research paper on net zero

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• My Account Login
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Open access
• Published: 20 October 2021

Energy systems in scenarios at net-zero CO 2 emissions

• Julianne DeAngelo   ORCID: orcid.org/0000-0001-9801-3288 1 ,
• Inês Azevedo 2 ,
• John Bistline 3 ,
• Leon Clarke 4 ,
• Gunnar Luderer   ORCID: orcid.org/0000-0002-9057-6155 5 ,
• Edward Byers   ORCID: orcid.org/0000-0003-0349-5742 6 &
• Steven J. Davis   ORCID: orcid.org/0000-0002-9338-0844 1 , 7  

Nature Communications volume  12 , Article number:  6096 ( 2021 ) Cite this article

18k Accesses

89 Citations

32 Altmetric

Metrics details

• Climate-change mitigation
• Energy economics
• Energy policy

Achieving net-zero CO 2 emissions has become the explicitgoal of many climate-energy policies around the world. Although many studies have assessed net-zero emissions pathways, the common features and tradeoffs of energy systems across global scenarios at the point of net-zero CO 2 emissions have not yet been evaluated. Here, we examine the energy systems of 177 net-zero scenarios and discuss their long-term technological and regional characteristics in the context of current energy policies. We find that, on average, renewable energy sources account for 60% of primary energy at net-zero (compared to ∼ 14% today), with slightly less than half of that renewable energy derived from biomass. Meanwhile, electricity makes up approximately half of final energy consumed (compared to ∼ 20% today), highlighting the extent to which solid, liquid, and gaseous fuels remain prevalent in the scenarios even when emissions reach net-zero. Finally, residual emissions and offsetting negative emissions are not evenly distributed across world regions, which may have important implications for negotiations on burden-sharing, human development, and equity.

Similar content being viewed by others

Expert review of the science underlying nature-based climate solutions

B. Buma, D. R. Gordon, … S. P. Hamburg

Australian human-induced native forest regeneration carbon offset projects have limited impact on changes in woody vegetation cover and carbon removals

Andrew Macintosh, Don Butler, … Paul Summerfield

Meta-analysis shows the impacts of ecological restoration on greenhouse gas emissions

Tiehu He, Weixin Ding, … Quanfa Zhang

Introduction

Limiting global mean temperature increase to 2 °C or even 1.5 °C relative to the preindustrial era 1 requires that global annual CO 2 emissions are net-zero or net-negative by the end of this century, and perhaps as soon as 2050 2 , 3 , 4 , 5 . In the broader context of climate stabilization, the magnitude of global temperature increase is directly proportional to cumulative CO 2 emissions, such that adding any amount of CO 2 to the atmosphere will increase future amounts of warming 2 , 6 . For these reasons, and because it is a clear and absolute target, achieving net-zero emissions is increasingly a goal of energy and emissions policies around the world 3 , 7 , 8 , 9 , 10 . Central to meeting this goal is a rapid and sweeping transformation of energy systems, including drastic reductions in the use of fossil fuels, substantial improvements in energy and materials efficiency, extensive electrification of energy end uses, and management of carbon 11 , 12 , 13 , 14 , 15 , 16 . Moreover, this transformation of energy systems must be reconciled with both sustainable development goals 17 , 18 and the considerable inertia of existing fossil energy infrastructure 19 .

Given this context, energy analysts are increasingly exploring the challenges and opportunities for net-zero emissions energy systems 20 , including detailed analyses of specific energy services and/or technologies 21 , 22 , 23 , 24 , 25 . A number of recent studies have examined the mitigation pathways of energy systems in integrated assessment model (IAM) scenarios that limit warming to below 1.5 °C 26 , 27 , 28 , 29 , 30 , providing insight about possible transformations of the energy-economy-land system. However, the common features and tradeoffs of such scenarios at the point when global CO 2 emissions reach net-zero have yet to be systematically assessed. These characteristics at the point of net-zero CO 2 can inform policies that might take varying approaches – including potential approaches that are not represented by current scenario pathways – to reach the same goal of net-zero emissions.

Here, we analyze 177 IAM scenarios from the public 1.5 °C Scenario Database (the SR1.5 database) 31 , 32 in which global sources and sinks (including land use and agriculture) reach net-zero CO 2 emissions by 2100 (see Supplementary Table  1 ). Details of our processing and analytic approach are described in the Methods section. In summary, we assess global and regional energy use, energy sources, residual emissions, electrification, and climate policy among the scenarios, finding robust features that span multiple IAMs 33 . For example, renewable sources represent roughly 60% of primary energy at the point when they reach net-zero CO 2 emissions—and often more than half of such renewable energy is provided by biomass. However, it is important to note that the scenario ensemble is not a representative sample that can be used to infer likelihood; individual scenarios are equally plausible given model constraints.

Energy use and timing of net-zero

Figure  1 shows the relationships among global energy and socioeconomic variables in the year of global net-zero emissions, broken out by the level of projected global warming. These categories include overshoot scenarios that return to the specified amount of warming by the end-of-century (see Methods). Among the 177 net-zero scenarios, those that avoid mean end-of-century warming of 1.5 °C (blue points) tend to have lower levels of global energy use (t-statistic = 9.2, p  < 0.001) and less GDP per capita (t-statistic = 8.6, p  < 0.001): of the 77 1.5 °C scenarios, GDP per capita is < $40,000 per person per year in 91% (median $27,914, range $20,103–$58,506) and total final energy use is <500 EJ in 69% (median 439 EJ, range 227–646; Fig.  1a ). In contrast, energy use and GDP per capita are substantially higher in scenarios that achieve net-zero emissions but exceed 1.5 °C (green and orange points): of the 100 2 °C and >2 °C scenarios, GDP per capita is < $40,000 per person per year in only 43% (median $43,642, range $20,299–$116,666) and total final energy use is <500 EJ in 24% (median 580 EJ, range 345–857; Fig.  1a ). Although this may reflect reduced energy use and economic activity in scenarios with the most ambitious mitigation, it is also related to when net-zero emissions occur in these scenarios. Supplementary Fig.  1 supports this idea by showing that warming level is not strongly related to the levels of energy use and GDP ultimately reached in net-zero scenarios. Figure  1b shows that the warmer scenarios achieve net-zero emissions in progressively later years (median for all scenarios = 2064, range 2037–2100), because the additional time for the economy and energy system to grow in these scenarios leads to higher cumulative CO 2 emissions (and therefore higher levels of subsequent warming). Supplementary Figs.  2 and 3 support this idea that more ambitious scenarios achieve lower levels of warming via faster energy system transformations. However, in contrast to the timing of net-zero, the timing of peak emissions is consistent across the scenarios (and essentially immediate): emissions peak in 2017 (range 2014–2027) for 1.5 °C scenarios, in 2019 (range 2011–2029) for 2 °C scenarios, and in 2022 (range 2010–2036) for >2 °C scenarios (Fig.  1b ). Although many scenarios show emissions peaking prior to 2019 (which did not occur), the regional, socio-economic, and technological representations that prevail when these scenarios achieve net-zero emissions may nonetheless provide valuable insights for net-zero emissions policies.

Scenarios that reach net-zero emissions show differences in energy use ( a ), emissions trajectory ( b ), energy sources ( c ), residual emissions ( d ), electrification ( e ), and policy ( f ), particularly with respect to warming levels (blue = <1.5 °C, green = <2.0 °C, orange = >2.0 °C). Points represent individual scenarios, with a frequency of scenarios shown along each axis for each warming level (colors corresponding to warming levels) and for all scenarios (black). Colored dashed lines and values indicate medians for warming groups, with colors corresponding to warming groups. Gray dashed lines indicate reference values for the year shown in gray.

Energy sources

The use and sources of renewable energy in net-zero scenarios vary considerably, with no obvious relationship to the level of warming (Fig.  1c ). Although the median share of primary energy derived from renewable sources (including biomass, solar, wind, hydroelectricity, and geothermal, using the direct equivalent method 34 ) is ∼ 60% regardless of warming level, in some cases it is as little as 25% and reaches 80% in a few others (Fig. 1c ). Similarly, the median share of these renewables that are not biomass is ∼ 55% regardless of warming level, but ranges from 20–89% (Fig. 1c ). Supplementary Fig.  4 further decomposes the sources of primary energy in net-zero scenarios, showing, for example, that the largest share of primary energy from nuclear is 23%, with nuclear more often contributing a small share of energy (median share across all scenarios is 4.8%, range 0–23.4%). Moreover, the share of primary energy from fossil fuels (coal, oil, and natural gas) in net-zero scenarios with and without carbon capture ranges from 3–64%, with a median share across all scenarios of 33% (Supplementary Fig.  4 ). By definition, in net-zero scenarios, any residual emissions to the atmosphere from the use of fossil fuels are offset by negative emissions strategies.

Residual emissions and electrification

The scale of residual emissions, i.e. emissions that are counter-balanced by equivalent carbon sequestration, is important to consider given many feasibility concerns about negative emissions technologies 33 , 35 . Figure  1d shows that the emissions intensity of final energy may remain quite high in net-zero scenarios (e.g., >30 Mt CO2/EJ compared to the current level of ∼ 80 Mt CO2/EJ). This residual emissions intensity is insensitive to the warming level or the energy intensity of the global economy (although lower warming scenarios do tend to have lower energy intensities based on median values by warming group; Fig. 1d ). Given that the points depicted in Fig.  1d are globally net-zero, the residual emissions are entirely offset by negative emissions.

Complementing the common assertion that everything must be electrified 36 , 37 , the scenario set indicates that reducing final energy use is also an important determinant for achieving 1.5 or 2 °C. Electricity accounts for 35–80% of final energy across the range of net-zero scenarios, but is <70% in most >2 °C scenarios (Fig.  1e ). Even though electrification is a useful mechanism for decarbonization, warmer scenarios tend to exhibit slightly higher levels of electrification at the timing of net-zero: median shares of 1.5 °C, 2 °C and >2 °C scenarios are 46% (range 35–80%), 51% (range 38–77%), and 53% (range 42–67%), respectively, perhaps because they afford greater time for end-uses to transition (Fig.  1e ). This transition-time effect on the amount of electrification is supported by Supplementary Fig.  3 , which shows that scenarios that are later in reaching net-zero tend to compensate with higher amounts of electrification (Supplementary Fig.  3e ). Warming amount is also correlated to both net-zero year ( r  = 0.73, p  < 0.001; Fig.  1b ) and electrification ( r  = 0.27, p  < 0.001) in the Fig.  1 global scenarios, which further supports the idea that warmer scenarios have slightly higher amounts of electrification because they reach net-zero emissions later, thus allowing more time for end-uses to transition and for costs to decline. However, these are subtle distinctions in comparison to the differences in per capita final energy use, where median shares in 1.5 °C, 2 °C and >2 °C scenarios increase from 47 to 63 to 75 GJ per person, respectively. For comparison, in 2019 the average American, EU, and Chinese citizen used approximately 202, 93, and 63 GJ, respectively. Thus, keeping final energy low is clearly important to meet 1.5 °C, while there is more flexibility in the level of electrification that is required.

Negative emissions and policy

The prevailing carbon prices in net-zero scenarios—a proxy for global climate policies—range from zero to > $1000/t CO 2 , yet with no clear relationship to either warming level or the amount of carbon sequestration through bioenergy with carbon capture and storage (BECCS) (Fig.  1f ; note that 16 scenarios with prices > $2000/t CO 2 are not shown). It is important to note that carbon prices in the majority of SR1.5 scenarios are endogenous “shadow” carbon prices that reflect the marginal cost of abatement, and thus do not directly reflect the impact of explicit (exogenous) carbon pricing such as a carbon tax or cap-and-trade system 33 , 38 , 39 . Only 23 of the 177 scenarios we analyze here include exogenous carbon pricing. The relationship between BECCS and carbon price should therefore be interpreted as the impact of marginal abatement cost on BECCS deployment. The lack of a clear relationship between the two does not necessarily mean that marginal abatement cost is inconsequential for the magnitude of negative emissions, but rather indicates that other dynamics relating to technology availability and costs may be the main drivers of BECCS deployment. Additionally, the median amount of carbon sequestration from BECCS increases in 1.5 °C, 2 °C and >2 °C scenarios, from 6.4 (range 0–16.7) to 8.0 (range 0–18.8) to 11.3 (range 3.7-16.4) Gt CO 2 , respectively (Fig.  1f ), indicating that warmer scenarios must rely on greater amounts negative emissions technologies to reach net-zero emissions.

Regional energy use, energy sources, and electrification

Figure  2 shows regional differences in energy and emissions among net-zero scenarios (in the year in which global CO 2 emissions are net-zero). In some cases, these differences are substantial and systematic. For example, Fig.  2a shows that when global emissions are net-zero, total final energy consumption is typically greatest in Asia (blue points) and the OECD and EU countries (e.g., the U.S., U.K., France, Germany, etc.; pink points)—in some cases more than 3 times the energy use in the Middle East and Africa, Latin America, and Eastern Europe (including Russia; yellow, green and purple points, respectively). Regional differences in GDP per capita in the net-zero year are somewhat less dramatic, but projections in the OECD and EU region are often greatest (median of $67,944 per person, range $47,534–$146,341), and projections in the Middle East and Africa are often lowest (median of $18,960 per person, range $6,263–$97,721; Fig.  2a ).

Scenarios that reach net-zero emissions globally ( n  = 172 scenarios with all regions) show regional differences in energy use ( a ), energy sources ( b ), electrification ( c ), and net emissions ( d ). Points represent individual scenarios, with a frequency of scenarios shown along each axis for each region (Asia = blue, Latin America = green, Middle East+Africa = orange, OECD + EU countries = pink, and Eastern Europe+Russia = purple). Colored dashed lines and values indicate medians for each region. Gray dashed lines indicate global reference values for the year shown in gray.

As in the case of globally aggregated energy sources (Fig.  1c ), the share of primary energy derived from renewables and different types of renewables are quite different across scenarios, with relatively little sensitivity to the region (Fig.  2b ). An exception is Latin America (green points), which most scenarios show having both a higher share of primary energy from renewables (median 80%, range 33–98%) and a greater share of those renewables from biomass (median 58%, range 12–83%) than other regions (median shares of renewables 58–67%, and median share of renewables from biomass 35–45%).

Regional variations in electrification are also small (regions’ median shares range from 43–52%), though final energy use per capita varies across regions in a pattern similar to GDP per capita (Fig.  2a and c ; Supplementary Fig.  5 ). Despite lower GDP per capita, energy use per capita in Eastern Europe and Russia is similar to the OECD and EU region (median energy use of 105 and 112 GJ/person, respectively) — considerably greater than in the other three regions, where median energy use ranges from 36–61 GJ/person (Fig.  2c ; note that Eastern Europe and Russia per capita final energy exceeded 200 GJ/person in 2 scenarios that are not shown).

Regional Distribution of Residual and Negative Emissions

Importantly, when global emissions are net-zero, emissions in many scenarios are still net-positive in some regions and (proportionately) net-negative in others. Figure  2d shows the regional balance of per capita residual emissions from energy and industry and per capita negative emissions from BECCS—i.e. net energy system emissions in the region (when points are compared to the dashed black line). These differences in residual (F-statistic = 141.6, p  < 0.001) and negative emissions (F-statistic = 70.7, p  < 0.001) across regions can be at least partially explained by differences in investment: Supplementary Fig.  6 shows that cumulative investment in non-fossil electricity supply up to the global net-zero year is correlated with regional electrification ( r  = 0.55, p  < 0.001), negative emissions from BECCS ( r  = 0.58, p  < 0.001), and residual emissions from energy and industry ( r  = 0.86, p  < 0.001; Supplementary Fig.  6 ). The positive correlation between non-fossil electricity investment and both BECCS and residual emissions is likely due to BECCS primarily being used to offset residual emissions, such that scenarios with high amounts of BECCS also have high amounts of residual emissions at net-zero. Of course, investment is not the only cost-related driver of these regional characteristics, but it does appear to play a significant role in the smaller subset of scenarios that include investment output values. Residual emissions per capita tend to be greater in regions of Eastern Europe and Russia and the OECD and EU, withmedian values of 1.9 (range 0.1–5.2) and 1.8 (range 0.2–4.9) t CO 2 /person, respectively (purple and pink points in Fig.  2d ). However, these regions also have greater per capita negative emissions from BECCS than Asia and the Middle East and Africa regions, such that they are net-negative in nearly as many scenarios (40.1% and 49.4% for Eastern Europe and Russia and OECD+EU, respectively) as they are net-positive (59.9% and 50.6%, respectively). In contrast, Latin America’s energy system is net-negative in 78.1% of the scenarios (green points) and the Middle East and Africa and Asia regions are net-negative in just 14.0% and 19.4%, respectively (orange and blue points). This supports recent research on regional and country-level negative emissions distributions in the context of regional net-zero emissions 40 , 41 and indicates that burden-sharing between currently less-developed regions may not be well-balanced in IAM outputs when global emissions reach net-zero. While there are many different approaches to defining a well-balanced mitigation effort 42 , burden-sharing approaches that consider equity as a key component are vital for meeting sustainable development goals 43 . Analysis of the SR1.5 scenarios in the context of equitable emissions/negative emissions allocation and sustainable development warrants further research.

Figure  3a shows the global distributions of residual and negative emissions in net-zero scenarios, including both those explicitly tied to the energy system (i.e. residual emissions from energy and industrial processes and negative emissions from BECCS) and those related to agriculture and land use (including afforestation and reforestation), which are major sources of negative emissions in many IAMs 44 . The aggregate patterns are striking: in warmer scenarios, net emissions from agriculture and land use tend to be less negative, residual emissions are higher, and these trends must be compensated for by larger negative emissions from BECCS (Fig.  3a ). In net-zero scenarios where warming is >2 °C, negative emissions from BECCS in the net-zero year are on average 10.5 Gt CO 2 , and in no scenario <3.7 Gt (range 3.7–16.4; Fig.  3a ). In contrast, there are some 1.5 °C and <2.0 °C scenarios in which there are no negative emissions from BECCS because more modest residual emissions are balanced by larger negative emissions from land uses (excluding BECCS), such as afforestation (Table  1 ). The negative emissions from BECCS also decrease in more ambitious mitigation scenarios, with mean values of 8.7 (range 0–18.8) Gt CO 2 and 6.7 (range 0–16.7) Gt CO 2 for <2.0 °C and 1.5 °C scenarios, respectively (Fig.  3a ; Table  1 ). Although residual emissions by end-use sector were not available for many of the scenarios we assessed, transportation was the dominant source of residual emissions in the 40 scenarios which report these details, followed by either the industry or residential and commercial sectors (see Supplementary Fig.  7 ).

Residual and negative emissions in net-zero scenarios show global differences across different warming levels ( a ) and regions ( b ). In each case, the boxes show the range from 25 th to 75 th percentiles, whiskers show the 5 th and 95 th percentiles, and the lines and circles within the boxes denote the median and mean values, respectively.

Global averages conceal considerable regional heterogeneity of emissions in a net-zero world. Figure  3b shows that potential negative emissions from land use are largest in Latin America (on average −1.1 Gt CO 2 in the net-zero year, range −4.8 to 1.7 Gt), while Asia is projected to be by far the largest source of residual emissions (on average 3.8 Gt CO 2 in the net-zero year, range 0.3–10.3 Gt). Asia and the OECD and EU regions are also the largest sources of negative emissions from BECCS, with an average of 2.5 (range 0–8.7) and 2.4 (range 0–6.0) Gt negative CO 2 emissions in the net-zero year, respectively; Fig.  3b ).

Relationships between scenario characteristics

Figure  4 compares all 177 net-zero scenarios according to 6 global characteristics in the net-zero year: the share of final energy that is electricity, the share of primary energy derived from renewables, the share of renewable energy that is derived from non-biomass sources, energy conservation (i.e. the inverse of per capita energy demand), the magnitude of negative emissions from BECCS, and net land-use emissions. Each panel in Fig.  4 sorts all the scenarios (rows) according to one of these characteristics (columns), with scenario values shown as z-scores. Pairwise correlation coefficients (r) are also shown at the top of each column to quantitatively compare each set of parameters (Supplementary Fig.  8 ). Plotted this way, for example in (a), it is evident that those scenarios in which electricity accounts for a greater share of final energy also tend to be associated with greater shares of renewable energy ( r  = 0.64, p  < 0.05) and non-biomass renewable energy ( r  = 0.59, p  < 0.05), but less energy conservation (i.e. greater per capita energy use, r  = −0.35, p  < 0.05; Fig.  4a ). Scenarios with greater shares of renewable energy tend to have higher shares of non-biomass renewable energy ( r  = 0.50, p  < 0.05; Fig.  4b ), while scenarios with greater amounts of energy conservation tend to have lower shares of non-biomass renewable energy, and vice versa ( r  = −0.46, p  < 0.05; Fig.  4c and d ). The relationship among these characteristics and the magnitude of negative emissions from BECCS and/or net land-use emissions is less clear, and maybe more dependent on the IAM or specific scenario used in each case. Since the process-based IAMs considered here use cost-effectiveness analysis (CEA) 33 , which minimizes the total mitigation costs of reaching a specified climate goal, all associations between output variables are essentially a reflection of what is cheapest. For example, in a scenario where substantial residual emissions remain at net-zero and are offset by correspondingly large amounts of negative emissions, reducing gross emissions to zero must have been more expensive than continuing to emit and offsetting with negative emissions. The most cost-effective outputs for scenarios are also based on the assumptions of individual models, including the availability and cost of technologies.

Panels show parameter standard deviations for scenarios (rows) sorted by ( a ) electrification, ( b ) renewables share, ( c ) non-biomass renewables share, ( d ) energy conservation, ( e ) negative emissions from BECCS, and ( f ) net land-use emissions. “Electrification” is the share of final energy consumed as electricity. “Renewables” is the share of primary energy supplied by biomass, solar, wind, hydroelectricity, and geothermal. “Non-biomass ren.” is the share of renewable energy sources provided by sources other than biomass. “Energy conservation” here reflects the inverse of final energy per capita, such that warmer colors indicate higher levels of energy consumption. “Negative ems-BECCS” is the total amount of negative emissions from bioenergy with carbon capture and storage. “Net ems-land use” is the net amount of global CO2 emissions related to land use. Mean and standard deviation for parameters are shown below each column, and pairwise correlation coefficients (r) are shown in bold at the top of each column. Black r-values are statistically significant ( p  < 0.05), while red r-values are not.

To further explore this relationship between negative emissions and other parameters, the underlying structure of the IAMs is important to consider: some of the SR1.5 models are partial equilibrium models (e.g., POLES ADVANCE) while others are general equilibrium (e.g. AIM-CGE 2.0 and 2.1) or hybrid models (e.g., MESSAGE-GLOBIOM 1.0) that link the two 31 . Additionally, certain scenarios have conditions that limit the amount or type of negative emissions technology used, such as EMF33_1.5C_limbio, which sets a limit of 100 EJ/year for the amount of bioenergy from BECCS, cellulosic fuels, and hydrogen 31 . Supplementary Fig.  9 shows the scenario ranges for residual emissions, non-biomass renewable energy share, and electrification for each model. These ranges demonstrate how the structure and assumptions of individual models affect the scenario outputs 45 , 46 : for example, GCAM scenarios tend to have systematically higher residual emissions and lower amounts of non-biomass renewable energy and electrification than those of other models (Supplementary Fig.  9 ). Such model differences are visible when comparing individual scenarios, but the output ranges tend to bemore sensitive to the scenario constraints than the models (Supplementary Fig.  10 ).

In addition to renewable and net-zero targets, “electrify everything” has become an explicit policy goal in a growing number of places 47 , particularly regarding heating and cooking in the residential and commercial sectors 48 , 49 and light-duty transportation 50 , 51 . In contrast, in most net-zero scenarios, electricity accounts for less than half (median 48.5%) of final energy (Fig.  1e ), including in the OECD and EU regions (Fig.  2c ). Although electricity makes up a greater fraction of final energy in all net-zero scenarios than it does today ( ∼ 20% today), in some regions and cases electricity remains less than 30% of final energy used (Fig. 2c ). This emphasizes that IAMs project considerable ongoing use of solid, liquid and gaseous fuels in hard-to-electrify sectors (such as construction, agriculture, aviation and shipping) even when emissions are net-zero (Supplementary Fig.  11 ). In this context, lower levels of final energy use per capita is one of the more robust trends of 1.5 °C scenarios. Meanwhile, our finding that electricity is somewhat less prevalent at the net-zero point in scenarios with lower warming may reflect the additional time available for end uses to electrify in less ambitious (higher warming) scenarios (Fig.  1e and b ).

Although the carbon intensity of final energy declines drastically in many net-zero scenarios compared to present ( ∼ 80 Mt CO2/EJ; Fig. 1d ), the absolute quantity of residual emissions remains substantial in many of the scenarios—as often as not >10 Gt CO 2 globally in the net-zero year (Fig.  3 ). This translates into prodigious quantities of negative emissions required, with perhaps proportional social, techno-economic and biophysical challenges 15 , 35 , 52 . But we also find that both the residual emissions and the negative emissions required to offset them are not evenly distributed across world regions (Figs.  2 d and 3b ), which may have important implications for human development and equity 53 . In particular, net-zero scenarios frequently show substantial negative emissions from land use in the Latin America region but the bulk of residual emissions occurring in other regions (Fig.  3b ). Although the magnitude of negative emissions is not strongly related to the composition of the energy system, those scenarios with greater quantities of negative emissions from BECCS seem to also have greater levels of final energy demand and lower shares of non-biomass renewables (e.g., solar, wind, hydro; Fig.  4e ). In contrast, the scenarios with greater negative emissions from land use (e.g., afforestation; represented by orange color in Fig.  4f ) also have higher final energy demand, but have higher shares of non-biomass renewables (Fig.  4f ). This reflects a logical trade-off in the availability of bioenergy and land-based carbon storage and suggests that the balance in IAMs outputs is being influenced by the level of future energy demand. However, it should be noted that prior studies have found that the value of negative emissions from BECCS will be more important than the value of generated electricity 54 , 55 .

Finally, the relationships between energy use, GDP, and likely warming amount show that energy use is often limited in net-zero scenarios, especially for scenarios that limit warming to a greater extent (Fig.  1a ). The median final energy consumption in global net-zero scenarios is 521 (range 227-857) EJ, compared to 418 EJ in 2019 56 . Given that global population is expected to reach nearly 9.5 billion by 2064 (median net-zero year) in SSP2 57 , if per capita energy use remains constant at ∼ 55 GJ/person, total final energy consumption will approach 523 EJ in 2064 – approximately equal to the net-zero scenario level. If instead per capita energy use continues to increase by about 0.16 GJ/person per year, as it did from 1971-2018 on average 56 , 58 , total final energy consumption will approach 588 EJ in 2064 – 67 EJ above the net-zero scenario level. So, in order to limit final energy use to ∼ 521 EJ in the median net-zero year, mean global per-capita energy use would have to remain nearly constant.

The process-based IAMs considered here have proven extraordinarily useful for articulating the overall shape of long-term mitigation pathways at a macro-regional to a global scale, but they are also limited in many ways that might influence our understanding of net-zero on a more detailed level. For example, because IAMs are designed to focus on larger-scale trends, they tend to have lower technological, temporal, and spatial resolutions compared with detailed energy system models 59 , 60 and do not consider the broad range of societal dynamics and political economy factors that can drive national emissions reduction strategies. Their strength in comprehensiveness is therefore balanced by limits to the detail in which they can represent regional or technological details that may be very relevant for actual strategy making, particularly with regard to rapid and disruptive technological change (e.g., management of electricity grids with high penetration of variable renewables, electric cars, greater digitalization, and hydrogen utilization pathways in heavy industry). Some studies have shown that because of this lower spatiotemporal detail, IAMs may be underestimating the role of variable renewables such as solar PV 60 , 61 . Furthermore, in this study we do not explicitly consider the detailed aspects of agriculture, forestry and other land use (AFOLU) sector and non-CO 2 emissions; however, these aspects are accounted for in the IAM frameworks themselves, which consistently include the linkages and tradeoffs between AFOLU and non-CO 2 emissions. The global full-economy representation provided by IAMs in this context makes them important tools in understanding pathways to net-zero greenhouse gas emissions balance as foreseen in Article 4 of the Paris Agreement. For all of these reasons, the net-zero scenarios we analyze here certainly do not reflect many of the details that will characterize net-zero emissions energy systems in the real world, but IAMs nonetheless remain critical bridges between more detailed energy systems models and long-term projections of climate change.

In the time since the SR1.5 database was released, increased efforts have been made to improve the model representation of key technologies, such as carbon-neutral liquid fuels, long-term storage of variable renewable energy, and negative emissions strategies. Given that these results show liquid fuels remaining prevalent and negative emissions strategies becoming increasingly important in the existing net-zero scenarios, such modeling improvements will be important to monitor going forward. The relationship between higher residual emissions and corresponding higher amounts of negative emissions in warmer scenarios points toward reducing residual emissions as a target for policy improvement, since negative emissions strategies are required to offset any amount of residual emissions at net-zero. Reliance on massive amounts of future negative emissions poses a substantial risk, given that there is still considerable uncertainty surrounding the feasibility of negative emissions technologies at such large scales 15 , 35 . Policies that support carbon-neutral fuels and technologies now would in turn reduce future reliance on large quantities of negative emissions to avoid harmful levels of warming. Our findings thus represent an opportunity to assess emerging net-zero emissions policies and energy trends in the context of the longer-term global goal of limiting climate change.

Data source

All of the model scenarios analyzed as part of this study were obtained from the public 1.5 °C Scenario Database (the SR1.5 database), hosted by the International Institute for Applied Systems Analysis (IIASA) through a process facilitated by the Integrated Assessment Modelling Consortium (doi: 10.5281/zenodo.3363345 | url: data.ene.iiasa.ac.at/iamc-1.5c-explorer). The model outputs in the database were generated by the various Integrated Assessment Models (IAMs) listed in Supplementary Table  S1 , and compiled by the Integrated Assessment Modeling Consortium (IAMC) 31 , 32 . The full scenario set was curated as part of the IPCC Special Report of Global Warming of 1.5 °C, Chapter 2 on mitigation pathways and details of the models and scenarios are detailed in the Technical Annex of the Chapter. The processes are described in more detail by Huppmann et al. 31 , 32 . In this paper we use version r2.0 of the all regions dataset. The 177 scenarios we assess here were produced by 7 main models (with 16 individual model variations), and thus are not truly independent of each other since each IAM has its own assumptions built into the model framework.

While an updated scenario database is being developed for the upcoming IPCC Sixth Assessment Report (AR6), our analysis is specifically about the characteristic of the net-zero energy system at the point of net-zero, and not the pathway up to that point. The broader insights of net-zero energy system characteristics gained from our analysis are thus valuable and we expect they won’t differ significantly in subsequent analyses of the next generation of (AR6) scenarios. Moreover, although recent developments in the power sector, e.g. renewables, have been faster than expected, the observed values for 2019–2020 are still within the range of the SR1.5 scenarios. For example, in 2020, approximately 2.9 EJ was generated from solar electricity 62 and the SR1.5 scenario outputs for Secondary Energy|Electricity|Solar in 2020 range from 0.2–6.6 EJ, with a median value of 1.8 EJ and a mean value of 2.4 EJ. For wind energy, approximately 5.9 EJ was generated in 2020 62 , and the SR1.5 scenario outputs for Secondary Energy|Electricity|Wind in 2020 range from 1.0–23.6 EJ, with a median value of 7.4 EJ and a mean value of 6.9 EJ.

IAMs have a long and sometimes controversial history in their efforts to characterize emissions pathways with the aim of mitigating climate change. The IAMs here are primarily what would be considered as complex “process-based” IAMs, as opposed to simpler “cost-benefit” IAMs that primarily simulate climate-economy relationships to estimate the social cost of carbon 63 .

They use a variety of over-arching modelling methods including linear programming, partial- and computable general equilibrium, and recursive-dynamic formulations. The models used tend to represent macro-economic regions, comprising large countries and trading blocs, ranging from a few to tens of regions with inter-regional trade of commodities, such as fuels and biomass. This regional information was aggregated in the IPCC SR1.5 process to a common 5-region definition (as above) to facilitate comparison. Temporal resolution is typically at 5 or 10-year timesteps, which is good for determining the levels of investments required, whilst abstractions need to be made to ensure that reliability of electricity systems remains plausible, such as ensuring that enough flexible reserve is available to meet peak electricity demands.

Scenarios representing climate policy tend to be implemented using carbon budget constraints that limit the cumulative carbon emissions over a period such that warming does not pass the desired level, e,g. 2 °C. Further scenario-related constraints may limit a wide range of parameters, such as technological options and shares, rates of change and diffusion etc.

The IAMs whose scenarios we assess here do not include feedbacks from climate impacts and damages, despite the fact that some studies have shown these could be substantial 64 , 65 . Rather the models are designed to inform mitigation efforts and have relatively simplistic representations of the Earth system 65 . Some IAMs are beginning to include feedbacks between, for example, temperature changes and energy use 66 , and more ambitious efforts are underway that will incorporate human energy, food and water systems into robust Earth system models 67 , 68 .

Filtering and analysis of scenarios

Our analysis includes only scenarios that reach net-zero CO 2 emissions by the end of this century (year 2100). We define the net-zero emissions year for each scenario (i.e., the x-axis in Fig.  1b ) as the first year that net global CO 2 emissions were equal to or less than zero. Because each model produces parameter outputs at 5 or 10 year time steps, we interpolated annual data using second-order polynomials.

We only consider CO 2 and not CH 4 or N 2 O for several reasons. First, many of the current net-zero policy targets are for net-zero CO 2 specifically 7 . Results from this analysis will therefore be relevant to those policies in the context of net-zero CO 2 . Second, entirely eliminating CH 4 or N 2 O emissions will entail the development of new technologies, particularly for removing these gases from the atmosphere 69 , such that there are not yet practicable pathways to net-zero for these gases 7 . Third, N 2 O is primarily related to agriculture, and our analysis is focused on the energy system.

The scenarios are categorized into 6 regions (global and the five world regions defined in the SR1.5 database) and 3 consolidated levels of end-of-century global warming, based on the wider set determined in the IPCC report:

1.5 °C, which includes “below 1.5 °C,” “1.5 °C return with low overshoot,” “1.5 °C return with high overshoot”;

2 °C, which includes “lower 2.0 °C” and “higher 2.0 °C,” and;

>2 °C, which corresponds to the category “above 2.0 °C”. These scenarios have >50% likelihood of exceeding global mean temperature change of 2.0 °C by 2100, with no set upper bound of temperature change.

These global warming outcomes are primarily characterized by the “likely” (>50% chance) of reaching the specified temperature level by 2100. Further sub-categories of “overshoot” scenarios, based on the peak-warming and then return to a stabilization temperature help identify between scenarios that rely on substantial amounts of net-negative emissions.

The output variables for IAMs in the SR1.5 database are not entirely consistent; some models have extensive lists of outputs and regional and sectoral breakdowns, while others have comparatively few outputs and are missing some variables altogether. Our analysis therefore relies only on those IAM scenarios that include all output variables required for our analysis (177 out of 202 total net-zero emissions scenarios from the SR1.5 database; see Supplementary Table  S1 ). Our interest in including as many scenarios as possible had to be balanced against our interest in exploring more detailed geographical and technological characteristics. Our analysis used the following 7 output variables: (1) CO 2 emissions (total net, energy and industrial processes net, AFOLU net), (2) Population, (3) GDP (PPP), (4) Primary energy, direct equivalent (total, fossil, nuclear, solar, wind, hydro, biomass), (5) Carbon Sequestration through BECCS, (6) Carbon price, and (7) Final energy (total and share from electricity). Residual CO 2 emissions were calculated by adding the residual emissions from energy and industrial processes (and, if applicable, the residual AFOLU emissions) to the amount of carbon sequestration from BECCS (since BECCS is used to offset residual emissions) in the net-zero year via the following equations:

If ‘Emissions|CO 2 |Energy and Industrial Processes’ is positive at net-zero:

‘Emissions|CO 2 |Residual Fossil’ = ‘Emissions|CO 2 |Energy and Industrial Processes’ + ‘Carbon Sequestration|CCS|Biomass’

If ‘Emissions|CO 2 |Energy and Industrial Processes’ is negative at net-zero:

‘Emissions|CO 2 |Residual Fossil’ = ‘Emissions|CO 2 |Energy and Industrial Processes’ + ‘Carbon Sequestration|CCS|Biomass’ + ‘Emissions|CO 2 |AFOLU’

All processing and analysis was done in JupyterLab (version 1.2.6). Code is available via GitHub: https://doi.org/10.5281/zenodo.5501623 70

Additional context for policymakers

Around the world, countries and jurisdictions are adopting energy policies that mandate high levels of renewable or zero-carbon electricity in the next few decades 8 , 9 . For example, in the U.S., 14 states (California, Colorado, Hawaii, Maine, Maryland, Massachusetts, Nevada, New Mexico, New Jersey, New York, Oregon, Vermont, Virginia, and Washington) have laws requiring that >50% of electricity come from renewables such as wind, solar and biomass (but often excluding large-scale hydropower). Such goals are consistent with our analysis of net-zero scenarios generated by IAMs; renewables (including hydro) account for >50% of all primary energy in 74% of the net-zero scenarios. However, many places have pledged or mandated 100% renewable electricity and/or 100% net-zero emissions economy-wide by 2050, including the proposed EU Climate Law, and laws or government orders in the U.S. states of Hawaii, New York, Washington and California. Although details of these plans vary, it is noteworthy that very few of the net-zero scenarios reflect these goals at the macro-region level. This is due to the way that sources and sinks, from energy and land-use sectors, and between CO 2 and non-CO 2 sources, are optimized over much larger spatial extents including the influence of inter-regional trade, rather than the aforementioned policies that are enacted at state- and country-level. For example, the share of primary energy derived from renewables in the first year of net-zero or net-negative emissions is <80% in all but 2 of the 177 scenarios (Fig.  1c ). Similarly, emissions in the OECD and EU region remain net-positive in more than half of the net-zero scenarios (pink points in Fig.  2d ). Thus, we advise caution when interpreting these results, to note that the aforementioned zero-carbon energy policies are not necessarily over-ambitious or inconsistent with global and macro-regional IAM scenarios, because other nearby places and regions (e.g., Middle East and Africa), are likely to still be net-positive at the point at which global CO 2 emissions hit net-zero (Fig.  2d ).

Data availability

All of the model scenarios analyzed as part of this study were obtained from the public 1.5 °C Scenario Database (the SR1.5 database), hosted by the International Institute for Applied Systems Analysis (IIASA) through a process facilitated by the Integrated Assessment Modelling Consortium ( https://doi.org/10.5281/zenodo.3363345 | url: data.ene.iiasa.ac.at/iamc-1.5c-explorer ).

Code availability

UNFCCC. Adoption of the Paris Agreement. (2015).

Matthews, H. D. & Caldeira, K. Stabilizing climate requires near-zero emissions. Geophys. Res. Lett. 35 , L04705 (2008).

Article   ADS   CAS   Google Scholar  

Rogelj, J. et al. Zero emission targets as long-term global goals for climate protection. Environ. Res. Lett. 10 , 105007 (2015).

Rogelj, J. et al. In Special Report on the impacts of global warming of 1.5   °C (Intergovernmental Panel on Climate Change, 2018).

Sanderson, B. M., O’Neill, B. C. & Tebaldi, C. What would it take to achieve the Paris temperature targets? Geophysical Research Letters https://doi.org/10.1002/2016GL069563 (2016).

Matthews, H. D., Gillett, N. P., Stott, P. A. & Zickfeld, K. The proportionality of global warming to cumulative carbon emissions. Nature 459 , 829–833 (2009).

Article   ADS   CAS   PubMed   Google Scholar  

Rogelj, J., Geden, O., Cowie, A. & Reisinger, A. Net-zero emissions targets are vague: three ways to fix. Nature 591 , 365–368 (2021).

IEA. Clean Energy Innovation. (Paris, France, 2020).

Ross, K. & Damassa, T. Assessing the Post-2020 Clean Energy Landscape. (World Resources Institute, Washington, D.C., 2015).

Peker, E. In The Wall Street Journal (Brussels, 2019).

Hoffert, M. I. et al. Energy implications of future stabilization of atmospheric CO 2 content. Nature 395 , 881–884 (1998).

IPCC. Mitigation of Climate Change. Contribution of Working Group III to the IPCC 5th Fifth Assessment Report of the Intergovernmental Panel on Climate Change . (Cambridge University Press, 2014).

GEA. Global Energy Assessment: Toward a Sustainable Future . (Cambridge University Press and the International Institute for Applied Systems Analysis, 2012).

Marcucci, A., Kypreos, S. & Panos, E. The road to achieving the long-term Paris targets: energy transition and the role of direct air capture. Climatic Change 144 , 181–193 (2017).

Article   ADS   Google Scholar  

Fuss, S. et al. Betting on negative emissions. Nat. Clim. Change 4 , 850–853 (2014).

Sachs, J. D., Schmidt-Traub, G. & Williams, J. Pathways to zero emissions. Nat. Geosci. 9 , 799–801 (2016).

McCollum, D. L. et al. Energy investment needs for fulfilling the Paris Agreement and achieving the Sustainable Development Goals. Nat. Energy 3 , 589–599 (2018).

Fay, M. et al. Decarbonizing Development; three steps to a Zero-Carbon Future. (World Bank Group, Washington, DC, 2015).

Tong, D. et al. Committed emissions from existing energy infrastructure jeopardize 1.5 °C climate target. Nature 572 , 373–377 (2019).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Davis, S. J. et al. Net-zero emissions energy systems. Science 360 , 1419 (2018).

Article   CAS   Google Scholar  

Jenkins, J. D., Luke, M. & Thernstrom, S. Getting to zero carbon emissions in the electric power sector. Joule 2 , 2498–2510 (2018).

Article   Google Scholar  

Dowling, J. A. et al. Role of long-duration energy storage in variable renewable electricity systems. Joule , https://doi.org/10.1016/j.joule.2020.07.007 (2020).

Audoly, R., Vogt-Schilb, A., Guivarch, C. & Pfeiffer, A. Pathways toward zero-carbon electricity required for climate stabilization. Appl. Energy 225 , 884–901 (2018).

Bataille, C. Physical and policy pathways to net-zero emissions industry. WIRES Wiley Interdisciplinary Reviews , 1–20, https://doi.org/10.1002/wcc.633 (2019).

Industrial transformation 2050 industrial transformation 2050: Pathways to net‐zero emisisons from EU heavy industry. (University of Cambridge Institute for Sustainable Leadership., Cambridge, England, 2019).

Fofrich, R. A. et al. Early retirement of power plants in climate mitigation scenarios. Environmental Research Letters , https://doi.org/10.1088/1748-9326/ab96d3 (2020).

Gambhir, A., Rogelj, J., Luderer, G., Few, S. & Napp, T. Energy system changes in 1.5 °C, well below 2 °C and 2 °C scenarios. Energy Strategy Reviews , https://doi.org/10.1016/j.esr.2018.12.006. (2019).

Rogelj, J. et al. Scenarios towards limiting global mean temperature increase below 1.5 °C. Nat. Clim. Change 8 , 325–332 (2018).

Luderer, G. et al. Residual fossil CO 2 emissions in 1.5–2 °C pathways. Nat. Clim. Change 8 , 626–633 (2018).

Grubler, A. et al. A low energy demand scenario for meeting the 1.5 °C target and sustainable development goals without negative emission technologies. Nat. Energy 3 , 515–527 (2018).

Huppmann, D. et al. (Integrated Assessment Modeling Consortium & International Institute for Applied Systems Analysis, 2018).

Huppmann, D., Rogelj, J., Krey, V., Kriegler, E. & Riahi, K. A new scenario resource for integrated 1.5 °C research. Nat. Clim. Change https://doi.org/10.1038/s41558-018-0317-4 (2018).

Rogelj, J. et al. In Global Warming of 1.5   °C. An IPCC Special Report on the impacts of global warming of 1.5   °C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty (Intergovernmental Panel on Climate Change, 2018).

Macknick, J. Energy and CO 2 emission data uncertainties. Carbon Manag. 2 , 189–205 (2014).

Smith, P. et al. Biophysical and economic limits to negative CO 2 emissions. Nat. Clim. Change 6 , 40–50 (2016).

ADS   Google Scholar  

Jaffe, A. M. in The Wall Street Journal (2021).

Roberts, D. in Vox (2017).

Guivarch, C. & Rogelj, J. Carbon price variations in 2 °C scenarios explored. (Carbon Pricing Leadership Coalition, USA, 2017).

Riahi, K. et al. The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: An overview. Glob. Environ. Change 42 , 153–168 (2017).

Honegger, M. & Reiner, D. The political economy of negative emissions technologies: consequences for international policy design. Clim. Policy 18 , 306–321 (2018).

van Soest, H. L., den Elzen, M. G. J. & van Vuuren, D. P. Net-zero emission targets for major emitting countries consistent with the Paris Agreement. Nat. Commun. 12 , 2140 (2021).

Article   ADS   PubMed   PubMed Central   CAS   Google Scholar  

Zhou, P. & Wang, M. Carbon dioxide emissions allocation: a review. Ecol. Econ. 125 , 47–59 (2016).

Cantore, N. & Padilla, E. Equality and CO 2 emissions distribution in climate change integrated assessment modelling. Energy 35 , 298–313 (2010).

Fuhrman, J., M., H., Doney, S. C., Shobe, W. & Clarens, A. F. Front. Clim. 1:11. (2019). From Zero to Hero?: Why Integrated Assessment Modeling of Negative Emissions Technologies Is Hard and How We Can Do Better. Front. Clim. 1 , 11 (2019).

Jaxa-Rozen, M. & Trutnevyte, E. Sources of uncertainty in long-term global scenarios of solar photovoltaic technology. Nat. Clim. Change 11 , 266–273 (2021).

Bistline, J. The importance of temporal resolution in modeling deep decarbonization of the electric power sector. Environmental Research Letters , https://doi.org/10.1088/1748-9326/ac10df (2021).

Mingle, J. In Yale 360 (2020).

Deason, J. & Borgeson, M. Electrification of buildings: potential, challenges, and outlook. Curr. Sustain./Renew. Energy Rep. 6 , 131–139 (2019).

Sugiyama, M. Climate change mitigation and electrification. Energy Policy 44 , 464–468 (2012).

Needell, Z., McNerney, J., Chang, M. & Trancik, J. Potential for widespread electrification of personal vehicle travel in the United States. Nat. Energy 1 , 16112 (2016).

Zhang, R. & Fujimori, S. The role of transport electrification in global climate change mitigation scenarios. Environ. Reseach Lett. 15 , 034019 (2020).

Hepburn, C. et al. The technological and economic prospects for CO 2 utilization and removal. Nature 575 , 87–97 (2019).

Pozo, C., Galán-Martín, Á., Reiner, D. M., Dowell, N. M. & Guillén-Gosálbez, G. Equity in allocating carbon dioxide removal quotas. Nat. Clim. Change 10 , 640–646 (2020).

M., F. et al. The economics of bioenergy with carbon capture and storage (BECCS) deployment in a 1.5 °C or 2 °C world. Glob. Environ. Change 68 , 102262 (2021).

Muratori, M., Calvin, K., Wise, M., Kyle, P. & Edmonds, J. Global economic consequences of deploying bioenergy with carbon capture and storage (BECCS). Environ. Reseach Lett. 11 , 095004 (2016).

IEA. World energy balances. IEA World Energy Statistics and Balances 2021 , https://doi.org/10.1787/data-00510-en (2021).

Samir, K. C. & Lutz, W. The human core of the Shared Socioeconomic Pathways: population scenarios by age, sex and level of education for all countries to 2100. Glob. Environ. Change 42 , 181–192 (2016).

Google Scholar  

World Development Indicators . (World Bank, 2019).

Bistline, J. et al. Energy storage in long-term system models: a review of considerations, best practices, and research needs. Prog. Energy 2 , 039601 (2020).

Gambhir, A., Butnar, I., Li, P., Smith, P. & Strachan, N. A review of criticisms of integrated assessment models and proposed approaches to address these, through the lens of BECCS. Energies 12 , 1747 (2019).

Creutzig, F. et al. The underestimated potential of solar energy to mitigate climate change. Nat. Energy 2 , 17140 (2017).

Global Energy Review 2021. (International Energy Agency, Paris, France, 2021).

Fisher-Vanden, K. & Weyant, J. The evolution of integrated assessment: developing the next generation of use-inspired integrated assessment tools. Annu. Rev. Resour. Econ. 12 , 471–487 (2020).

Woodard, D. L., Davis, S. J. & Randerson, J. T. Economic carbon cycle feedbacks may offset additional warming from natural feedbacks. Proc. Natl Acad. Sci. 116 , 759–764 (2018).

Calvin, K. & Bond-Lamberty, B. I. Integrated human-earth system modeling—state of the science and future directions. Environ. Reseach Lett. 13 , 063006 (2018).

Calvin, K. et al. GCAM v5.1: representing the linkages between energy, water, land, climate, and economic systems. Geoscientific Model Dev. 12 , 677–698 (2019).

Calvin, K. et al. Characteristics of human-climate feedbacks differ at different radiative forcing levels. Glob. Planet. Change 180 , 126–135 (2019).

Collins, W. D. et al. The integrated Earth system model version 1: formulation and functionality. Geoscientific Model Dev. 8 , 2203–2219 (2015).

Jackson, R. B., Solomon, E. I., Canadell, J. G., Cargnello, M. & Field, C. B. Methane removal and atmospheric restoration. Nat. Sustainability 2 , 436–438 (2019).

DeAngelo, J. et al. Energy systems in scenarios at net-zero CO 2 emissions. net-zero-scenarios, https://doi.org/10.5281/zenodo.5501623, 2021.

Download references

Acknowledgements

The authors are grateful to Jinhyuk E. Kim for help in pre-processing scenario data. J.D. and S.J.D. acknowledge support from the U.S. National Science Foundation (INFEWS grant EAR 1639318). U.S. National Science Foundation (INFEWS grant EAR 1639318).

Author information

Authors and affiliations.

Department of Earth System Science, University of California, Irvine, Irvine, CA, USA

Julianne DeAngelo & Steven J. Davis

Department of Earth System Science, Stanford University, Stanford, CA, USA

Inês Azevedo

Electric Power Research Institute, Palo Alto, CA, USA

John Bistline

School of Public Policy, University of Maryland, College Park, MD, USA

Leon Clarke

Potsdam Institute for Climate Impact Research, Potsdam, Germany

Gunnar Luderer

Energy Program, International Institute for Applied Systems Analysis, Laxenburg, Austria

Edward Byers

Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA, USA

Steven J. Davis

You can also search for this author in PubMed   Google Scholar

Contributions

S.J.D. and J.D. conceived the study. J.D. performed the analyses, with support from G.L., E.B., J.B. and S.J.D. J.D. and S.J.D. led the writing with input from I.A., J.B., G.L., E.B. and L.C.

Corresponding author

Correspondence to Julianne DeAngelo .

Ethics declarations

Competing interests.

The authors declare no competing interests.

Additional information

Peer review information Nature Communications thanks Andres Clarens, Zhifu Mi, and Francesco Lamperti for their contribution to the peer review of this work. Peer reviewer reports are available.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary information, peer review file, rights and permissions.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Cite this article.

DeAngelo, J., Azevedo, I., Bistline, J. et al. Energy systems in scenarios at net-zero CO 2 emissions. Nat Commun 12 , 6096 (2021). https://doi.org/10.1038/s41467-021-26356-y

Download citation

Received : 01 March 2021

Accepted : 28 September 2021

Published : 20 October 2021

DOI : https://doi.org/10.1038/s41467-021-26356-y

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

This article is cited by

A cross-scale framework for evaluating flexibility values of battery and fuel cell electric vehicles.

• Benben Jiang

Nature Communications (2024)

MEIC-global-CO2: A new global CO2 emission inventory with highly-resolved source category and sub-country information

• Ruochong Xu
• Qiang Zhang

Science China Earth Sciences (2024)

Solar technology‒closed loop synergy facilitates low-carbon circular bioeconomy in microalgal wastewater treatment

• Praveen Kuppan
• Abinandan Sudharsanam
• Mallavarapu Megharaj

npj Clean Water (2023)

Second-life battery systems for affordable energy access in Kenyan primary schools

• Nisrine Kebir
• Alycia Leonard
• Stephanie A. Hirmer

Scientific Reports (2023)

Large global variations in the carbon dioxide removal potential of seaweed farming due to biophysical constraints

• Isabella B. Arzeno-Soltero
• Benjamin T. Saenz
• Kristen A. Davis

Communications Earth & Environment (2023)

By submitting a comment you agree to abide by our Terms and Community Guidelines . If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Carbon Neutrality : aiming for a net-zero carbon future

• Open access
• Published: 19 April 2022
• Volume 1 , article number  2 , ( 2022 )

Cite this article

You have full access to this open access article

• Changying Zhao 1  

4243 Accesses

6 Citations

11 Altmetric

Explore all metrics

Avoid common mistakes on your manuscript.

Greenhouse gas emissions have increased rapidly and global warming is an emerging huge threat to the human society since the industrial revolution. In 2015 the Paris Agreement set a global goal to achieve carbon neutrality in the second half of the century, and more than 130 countries have been committed to this goal. Carbon neutrality is a multi-disciplinary and comprehensive research area involving energy, environment, finance, management, and other disciplines. For example, the research in low-carbon energy transition not only covers related technologies such as renewables and energy storage, carbon capture, utilization and storage (CCUS), etc., but also involves social sciences topics including climate change investment and financing, carbon management, circular economy, etc. At present, there is no one comprehensive journal which can cover the above topics. Although several journals involve some aspects of low-carbon research, the coverage is quite narrow, mostly focusing on one single discipline such as energy, environmental or policy study. The lack of cross-disciplinary research in the low-carbon area has seriously hindered the rapid development and promotion of net-zero carbon technologies, policies and ideas. In view of this, Shanghai Jiao Tong University and Springer Nature jointly launched the journal of Carbon Neutrality in 2021.

Focused on low carbon energy, climate change, ecosystem and environmental governance, carbon finance and carbon management, Carbon Neutrality aims to establish itself as a flagship and leading international journal in the field of low carbon, publishing advanced and up-to-date original research and review papers with the highest quality in the area. The journal intends to create a cutting-edge international platform for scientists, engineers, policy makers, and entrepreneurs to exchange scientific and technological knowledge and explore effective carbon neutrality pathways and climate change solutions with shared expertise.

The Editorial Board of Carbon Neutrality consists of more than 40 prominent and world-leading experts. The research interests of the Editorial Board cover various disciplines such as low-carbon energy, low-carbon environment, carbon finance and carbon management, which lays a solid foundation for the high-quality development of the journal.

With the official publication of the first issue of Carbon Neutrality , I would like to express my sincere gratitude to the authors, reviewers, Editorial Board Members and editorial office staff for their support and valuable contributions to the journal. We cordially invite more and more low-carbon experts worldwide to join us in contributing manuscripts and witnessing the development of Carbon Neutrality . I believe, with our joint efforts, Carbon Neutrality will become a world-leading journal promoting the global research in feasible solutions for climate change as well as optimal pathways to net-zero emissions.

Author information

Authors and affiliations.

Shanghai Jiao Tong University, Shanghai, China

Changying Zhao

You can also search for this author in PubMed   Google Scholar

Contributions

All the authors read and approved the final manuscript.

Corresponding author

Correspondence to Changying Zhao .

Ethics declarations

Competing interests.

The authors declare that they have no competing interests.

Additional information

Publisher’s note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Zhao, C. Carbon Neutrality : aiming for a net-zero carbon future. Carb Neutrality 1 , 2 (2022). https://doi.org/10.1007/s43979-022-00013-9

Download citation

Published : 19 April 2022

DOI : https://doi.org/10.1007/s43979-022-00013-9

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Find a journal
• Publish with us
• Track your research

• Ways to Give
• Contact an Expert
• Explore WRI Perspectives

Filter Your Site Experience by Topic

Applying the filters below will filter all articles, data, insights and projects by the topic area you select.

• All Topics Remove filter
• Climate filter site by Climate
• Cities filter site by Cities
• Energy filter site by Energy
• Food filter site by Food
• Forests filter site by Forests
• Freshwater filter site by Freshwater
• Ocean filter site by Ocean
• Business filter site by Business
• Economics filter site by Economics
• Finance filter site by Finance
• Equity & Governance filter site by Equity & Governance

Search WRI.org

Not sure where to find something? Search all of the site's content.

What Does "Net-Zero Emissions" Mean? 8 Common Questions, Answered

• climate science
• carbon removal
• Paris Agreement
• climate policy
• greenhouse gases

Editor's Note: This article was updated in March 2023 to include WRI’s latest research and information about new national net-zero targets.

The latest  climate science  is clear: Limiting global warming to 1.5 degrees C (2.7 degrees F) is still possible. But to avoid the worst climate impacts, global greenhouse gas (GHG) emissions will need to  drop by nearly half by 2030  and ultimately reach net zero.

Recognizing this urgency, a rapidly growing number of national governments, local governments and business leaders are making commitments to reach net-zero emissions within their jurisdictions or businesses. To date,  over 90 countries  have communicated such “net-zero targets,” including the world’s largest emitters (China, the United States and India). On top of that, hundreds more regions, cities and companies have set targets of their own.

But what does a net-zero target mean, what’s the science behind net zero and which countries have already made such commitments? Here are answers to eight common questions:

1. What Does Net-Zero Emissions Mean?

Net-zero emissions, or “net zero,” will be achieved when all emissions released by human activities are counterbalanced by removing carbon from the atmosphere in a process known as  carbon removal .

Achieving net zero will require a two-part approach: First and foremost, human-caused emissions (such as those from fossil-fueled vehicles and factories) should be reduced as close to zero as possible. Any remaining emissions should then be balanced with an equivalent amount of carbon removal, which can happen through natural approaches like restoring forests or through technologies like  direct air capture and storage  (DACS), which scrubs carbon directly from the atmosphere.

2. When Does the World Need to Reach Net-Zero Emissions?

Under the Paris Agreement, countries agreed to limit warming to well below 2 degrees C (3.6 degrees F), ideally to  1.5 degrees C  (2.7 degrees F). Global climate impacts that are already unfolding under the current  1.1 degrees C  (1.98 degrees F) of warming — from melting ice to devastating heat waves and more intense storms — show the urgency of minimizing temperature increase.

The  latest science  suggests that limiting warming to 1.5 degrees C depends on CO2 emissions reaching net zero between 2050 and 2060.  Reaching net zero earlier in that range (closer to 2050) avoids a risk of temporarily "overshooting," or exceeding 1.5 degrees C. Reaching net zero later (nearer to 2060) almost guarantees surpassing 1.5 degrees C for some time before global temperature can be reduced back to safer limits through carbon removal.

Critically, the sooner  emissions peak , and the lower they are at that point, the more realistic achieving net zero becomes. This would also create less reliance on carbon removal in the second half of the century.

This does not suggest that all countries need to reach net-zero emissions at the same time. However, the chances of limiting warming to 1.5 degrees C depend significantly on how soon the highest emitters reach net zero. Equity-related considerations — including responsibility for past emissions, equality in per-capita emissions and capacity to act — also suggest earlier dates for wealthier, higher-emitting countries.

Importantly, the time frame for reaching net-zero emissions is different for CO2 alone versus for CO2 plus other greenhouse gases like methane, nitrous oxide and fluorinated gases. For non-CO2 emissions, the net zero date is later, in part because models assume that some of these emissions — such as methane from agricultural sources — are more difficult to phase out. However, these potent but short-lived gases will  drive temperatures higher  in the near term, potentially pushing temperature change past the 1.5 degrees C threshold much earlier.

Because of this, it's important for countries to specify whether their net-zero targets cover CO2 only or all GHGs. A comprehensive net-zero emissions target would include all GHGs, ensuring that non-CO2 gases are also reduced with urgency.

3. Is the World on Track to Reach Net-Zero Emissions on Time?

No — despite the enormous benefits of climate action to date, progress is happening far too slowly for the world to hold temperature rise to 1.5 degrees C (2.7 degrees F). The UN finds  that climate policies currently in place point to a 2.8 degrees C temperature rise by the end of the century.

4. What Needs to Happen to Achieve Net-Zero Emissions?

To achieve net-zero emissions, rapid transformation will be required across all global systems — from how we power our economies, to how we transport people and goods and feed a growing population.

For example, in pathways to 1.5 degrees C, zero-carbon sources will need to supply  98%-100% of electricity by 2050 . Energy efficiency and fuel-switching measures are critical for reducing emissions from transportation. Improving the efficiency of food production, changing dietary choices,  restoring degraded lands  and reducing food loss and waste  also have significant potential  to reduce emissions.

Additionally, action must be taken to reverse course in cases where change is at a standstill or headed in the wrong direction entirely. For instance , efforts to phase out unabated coal remain well off-track and must decline six times faster by 2030. The world also needs to halt deforestation and increase tree cover gain two times faster by 2030.

It is critical that the structural and economic transition toward net zero is approached in a just manner , especially for workers tied to high-carbon industries. Indeed, the costs and benefits of transitioning to a net-zero emissions economy must be distributed equitably.

The good news is that most of the technologies needed to unlock net zero are already available and increasingly cost-competitive with high-carbon alternatives. Solar and wind now provide the  cheapest power  available for most of the world. Markets are waking up to these opportunities and to the risks of a high-carbon economy, and they are shifting accordingly.

Investments in carbon removal techniques are also necessary. The different pathways assessed by the IPCC to achieve 1.5 degrees C  all rely on carbon removal to some extent . Removing CO2 from the atmosphere will compensate for emissions from sectors in which reaching net-zero emissions is more difficult, such as aviation.

5. How Many Countries Have Set Net-Zero Targets?

Global momentum for setting net-zero targets is growing quickly, with key economies like China, the United States, India and the European Union articulating such commitments. Bhutan was the first country to set a net-zero target in 2015. Now over 90 countries, representing nearly 80% of global emissions, are covered by a net-zero target.

Climate Watch’s  Net-Zero Tracker  shows how these targets were set, such as through nationally determined contributions (NDCs), long-term low GHG emissions development strategies (long-term strategies), domestic laws, policies, or high-level political pledges from heads of state or other cabinet members. The tracker also includes information on the scope of national net-zero targets, providing details about the GHGs and sectors covered by each, the extent to which the target relies on international offsets and more.

6. Does the Paris Agreement Commit Countries to Achieving Net-Zero Emissions?

In short, yes. Specifically, the Paris Agreement sets a  long-term goal  of achieving "a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century, on the basis of equity, and in the context of sustainable development and efforts to eradicate poverty." This concept of balancing emissions and removals is akin to reaching net-zero emissions.

The  Glasgow Climate Pact , signed at COP26 and marking the five-year anniversary of the Paris Agreement, also emphasized the importance of setting ambitious net zero goals. The pact urges countries to move “towards just transitions to net zero emissions by or around midcentury, taking into account different national circumstances.”  To this end, it encourages parties “that have not yet done so to communicate…long-term low greenhouse gas emission development strategies” that set the country on a pathway toward net zero. The shift from “in the second half of this century” to “by or around mid-century” reflects a notable increase in perceived urgency.

7. Why and How Should Countries Align Their Near-term Emissions Reduction Targets with Longer-term Net-Zero Goals?

Countries typically set net-zero targets for around 2050 — nearly three decades from now. However, to ensure that the world gets on the right track toward reaching net zero, those long-term objectives must guide and inform near-term action today. This will help avoid  locking in  carbon-intensive, non-resilient infrastructure and technologies. Countries can also cut near- and long-term costs by investing in green infrastructure that will not need to be phased out later, designing consistent policies and sending strong signals to the private sector to invest in climate action.

Under the Paris Agreement, countries agreed to submit climate plans every five years, known as  nationally determined contributions (NDCs ). NDCs, which currently target 2030, are an important tool to align near- and long-term emissions reduction goals. When informed by a country’s long-term vision, these documents can help governments implement the policies necessary today to realize an ambitious mid-century objective.

Many countries with net-zero targets are beginning to incorporate them directly into their NDCs, particularly now that the Glasgow Climate Pact “notes the importance of aligning nationally determined contributions with long-term low greenhouse gas emission development strategies.”

8. Are Net-Zero Targets a Form of Greenwashing?

Not necessarily, but they can be if used as an excuse to not take bold climate action in the near term.

Although net-zero targets continue to gain traction with governments and companies, skeptical voices have emerged, from  academic journals  to  Greta Thunberg’s speech  in Davos. Critiques of net-zero targets include:

The “net” aspect of net-zero targets could dampen efforts to rapidly cut emissions.

Critics are concerned that this could foster an overreliance on carbon removal, allowing decision-makers to use net-zero targets to avoid emission reductions in the near term. Decision-makers can address this concern by setting ambitious gross reduction targets (targets that do not rely on removals) alongside their longer-term net reduction targets.

Some countries’ net-zero targets rely on purchasing emissions reductions, delaying reductions within their own boundaries.

Some countries are setting net-zero targets that rely on carbon offsetting, which involves investing in or paying for emissions reductions from other countries to use toward their own targets. There’s concern that government leaders might use this strategy to avoid reducing their own emissions in the long term. Decision-makers can address this concern by setting deep emission reduction targets that explicitly avoid or limit using offsets to achieve their goals.

WRI’s experts are closely following the UN climate talks. Watch our  Resource Hub  for new articles, research, webinars and more.

The time horizon for net-zero targets — typically 2050 — feels distant.

Today’s infrastructure can last for decades and have a major impact on mid-century targets. Decision-makers must take this into account by establishing near- and mid-term milestones for their path to net-zero emissions, including by setting ambitious 2030 emission reduction targets as part of their NDCs. NDCs are subject to transparency and accountability mechanisms under the Paris Agreement that can foster implementation in the near term, which is critical for a long-term net-zero goal to be credible.

In short, net-zero commitments must be robust  to be effective and advance climate action. Countries must take concrete steps to ensure this if they are to effectively address the challenge at hand.

Relevant Work

Designing and communicating net-zero targets, your country set a net-zero target: what's next, tracking climate action: how the world can still limit warming to 1.5 degrees c, how you can help.

WRI relies on the generosity of donors like you to turn research into action. You can support our work by making a gift today or exploring other ways to give.

Stay Informed

World Resources Institute 10 G Street NE Suite 800 Washington DC 20002 +1 (202) 729-7600

© 2024 World Resources Institute

Join our live presentation on Jan 23rd as we present four stories that will shape 2024, followed by a live Q&A.

Together, we can unleash the positive, tangible and system-wide transformations needed to protect our planet for this and future generations.

Create an account

Create a free IEA account to download our reports or subcribe to a paid service.

Net Zero by 2050

A Roadmap for the Global Energy Sector

This report is part of Net Zero Emissions

About this report

The number of countries announcing pledges to achieve net zero emissions over the coming decades continues to grow. But the pledges by governments to date – even if fully achieved – fall well short of what is required to bring global energy-related carbon dioxide emissions to net zero by 2050 and give the world an even chance of limiting the global temperature rise to 1.5 °C. This special report is the world’s first comprehensive study of how to transition to a net zero energy system by 2050 while ensuring stable and affordable energy supplies, providing universal energy access, and enabling robust economic growth. It sets out a cost-effective and economically productive pathway, resulting in a clean, dynamic and resilient energy economy dominated by renewables like solar and wind instead of fossil fuels. The report also examines key uncertainties, such as the roles of bioenergy, carbon capture and behavioural changes in reaching net zero.

Summary for policy makers

Reaching net zero emissions globally by 2050 is a critical and formidable goal.

The energy sector is the source of around three-quarters of greenhouse gas emissions today and holds the key to averting the worst effects of climate change, perhaps the greatest challenge humankind has faced. Reducing global carbon dioxide (CO 2 ) emissions to net zero by 2050 is consistent with efforts to limit the long-term increase in average global temperatures to 1.5˚C. This calls for nothing less than a complete transformation of how we produce, transport and consume energy. The growing political consensus on reaching net zero is cause for considerable optimism about the progress the world can make, but the changes required to reach net zero emissions globally by 2050 are poorly understood. A huge amount of work is needed to turn today’s impressive ambitions into reality, especially given the range of different situations among countries and their differing capacities to make the necessary changes. This special IEA report sets out a pathway for achieving this goal, resulting in a clean and resilient energy system that would bring major benefits for human prosperity and well-being.

The global pathway to net zero emissions by 2050 detailed in this report requires all governments to significantly strengthen and then successfully implement their energy and climate policies. Commitments made to date fall far short of what is required by that pathway. The number of countries that have pledged to achieve net zero emissions has grown rapidly over the last year and now covers around 70% of global emissions of CO 2 . This is a huge step forward. However, most pledges are not yet underpinned by near-term policies and measures. Moreover, even if successfully fulfilled, the pledges to date would still leave around 22 billion tonnes of CO 2 emissions worldwide in 2050. The continuation of that trend would be consistent with a temperature rise in 2100 of around 2.1 °C. Global emissions fell in 2020 because of the Covid-19 crisis but are already rebounding strongly as economies recover. Further delay in acting to reverse that trend will put net zero by 2050 out of reach.

In this Summary for Policy Makers, we outline the essential conditions for the global energy sector to reach net zero CO 2 emissions by 2050. The pathway described in depth in this report achieves this objective with no offsets from outside the energy sector, and with low reliance on negative emissions technologies. It is designed to maximise technical feasibility, cost-effectiveness and social acceptance while ensuring continued economic growth and secure energy supplies. We highlight the priority actions that are needed today to ensure the opportunity of net zero by 2050 – narrow but still achievable – is not lost. The report provides a global view, but countries do not start in the same place or finish at the same time: advanced economies have to reach net zero before emerging markets and developing economies, and assist others in getting there. We also recognise that the route mapped out here is a path, not necessarily the path, and so we examine some key uncertainties, notably concerning the roles played by bioenergy, carbon capture and behavioural changes. Getting to net zero will involve countless decisions by people across the world, but our primary aim is to inform the decisions made by policy makers, who have the greatest scope to move the world closer to its climate goals.

Net zero by 2050 hinges on an unprecedented clean technology push to 2030

The path to net zero emissions is narrow: staying on it requires immediate and massive deployment of all available clean and efficient energy technologies. In the net zero emissions pathway presented in this report, the world economy in 2030 is some 40% larger than today but uses 7% less energy. A major worldwide push to increase energy efficiency is an essential part of these efforts, resulting in the annual rate of energy intensity improvements averaging 4% to 2030 – about three-times the average rate achieved over the last two decades. Emissions reductions from the energy sector are not limited to CO 2 : in our pathway, methane emissions from fossil fuel supply fall by 75% over the next ten years as a result of a global, concerted effort to deploy all available abatement measures and technologies.

Ever-cheaper renewable energy technologies give electricity the edge in the race to zero. Our pathway calls for scaling up solar and wind rapidly this decade, reaching annual additions of 630 gigawatts (GW) of solar photovoltaics (PV) and 390 GW of wind by 2030, four-times the record levels set in 2020. For solar PV, this is equivalent to installing the world’s current largest solar park roughly every day. Hydropower and nuclear, the two largest sources of low-carbon electricity today, provide an essential foundation for transitions. As the electricity sector becomes cleaner, electrification emerges as a crucial economy-wide tool for reducing emissions. Electric vehicles (EVs) go from around 5% of global car sales to more than 60% by 2030.  

Priority action: Make the 2020s the decade of massive clean energy expansion

All the technologies needed to achieve the necessary deep cuts in global emissions by 2030 already exist, and the policies that can drive their deployment are already proven.

As the world continues to grapple with the impacts of the Covid-19 pandemic, it is essential that the resulting wave of investment and spending to support economic recovery is aligned with the net zero pathway. Policies should be strengthened to speed the deployment of clean and efficient energy technologies. Mandates and standards are vital to drive consumer spending and industry investment into the most efficient technologies. Targets and competitive auctions can enable wind and solar to accelerate the electricity sector transition. Fossil fuel subsidy phase-outs, carbon pricing and other market reforms can ensure appropriate price signals. Policies should limit or provide disincentives for the use of certain fuels and technologies, such as unabated coal-fired power stations, gas boilers and conventional internal combustion engine vehicles. Governments must lead the planning and incentivising of the massive infrastructure investment, including in smart transmission and distribution grids.

Electric car sales in the net zero pathway, 2020-2030

Capacity additions of solar pv and wind in the net zero pathway, 2020-2030, energy intensity of gdp in the net zero pathway, 2020-2030, net zero by 2050 requires huge leaps in clean energy innovation.

Reaching net zero by 2050 requires further rapid deployment of available technologies as well as widespread use of technologies that are not on the market yet. Major innovation efforts must occur over this decade in order to bring these new technologies to market in time. Most of the global reductions in CO 2 emissions through 2030 in our pathway come from technologies readily available today. But in 2050, almost half the reductions come from technologies that are currently at the demonstration or prototype phase. In heavy industry and long-distance transport, the share of emissions reductions from technologies that are still under development today is even higher.

The biggest innovation opportunities concern advanced batteries, hydrogen electrolysers, and direct air capture and storage. Together, these three technology areas make vital contributions the reductions in CO 2 emissions between 2030 and 2050 in our pathway. Innovation over the next ten years – not only through research and development (R&D) and demonstration but also through deployment – needs to be accompanied by the large-scale construction of the infrastructure the technologies will need. This includes new pipelines to transport captured CO 2 emissions and systems to move hydrogen around and between ports and industrial zones.

Priority action: Prepare for the next phase of the transition by boosting innovation

Clean energy innovation must accelerate rapidly, with governments putting R&D, demonstration and deployment at the core of energy and climate policy.

Government R&D spending needs to be increased and reprioritised. Critical areas such as electrification, hydrogen, bioenergy and carbon capture, utilisation and storage (CCUS) today receive only around one-third of the level of public R&D funding of the more established low-carbon electricity generation and energy efficiency technologies. Support is also needed to accelerate the roll-out of demonstration projects, to leverage private investment in R&D, and to boost overall deployment levels to help reduce costs. Around USD 90 billion of public money needs to be mobilised globally as soon as possible to complete a portfolio of demonstration projects before 2030. Currently, only roughly USD 25 billion is budgeted for that period. Developing and deploying these technologies would create major new industries, as well as commercial and employment opportunities.

Annual CO2 emissions savings in the net zero pathway, 2030 and 2050, relative to 2020

The transition to net zero is for and about people.

A transition of the scale and speed described by the net zero pathway cannot be achieved without sustained support and participation from citizens. The changes will affect multiple aspects of people’s lives – from transport, heating and cooking to urban planning and jobs. We estimate that around 55% of the cumulative emissions reductions in the pathway are linked to consumer choices such as purchasing an EV, retrofitting a house with energy-efficient technologies or installing a heat pump. Behavioural changes, particularly in advanced economies – such as replacing car trips with walking, cycling or public transport, or foregoing a long-haul flight – also provide around 4% of the cumulative emissions reductions.

Providing electricity to around 785 million people that have no access and clean cooking solutions to 2.6 billion people that lack those options is an integral part of our pathway. Emissions reductions have to go hand-in-hand with efforts to ensure energy access for all by 2030. This costs around USD 40 billion a year, equal to around 1% of average annual energy sector investment, while also bringing major co-benefits from reduced indoor air pollution.

Some of the changes brought by the clean energy transformation may be challenging to implement, so decisions must be transparent, just and cost-effective. Governments need to ensure that clean energy transitions are people-centred and inclusive. Household energy expenditure as a share of disposable income – including purchases of efficient appliances and fuel bills – rises modestly in emerging market and developing economies in our net zero pathway as more people gain access to energy and demand for modern energy services increases rapidly. Ensuring the affordability of energy for households demands close attention: policy tools that can direct support to the poorest include tax credits, loans and targeted subsidies.

Priority action: Clean energy jobs will grow strongly but must be spread widely

Energy transitions have to take account of the social and economic impacts on individuals and communities, and treat people as active participants.

The transition to net zero brings substantial new opportunities for employment, with 14 million jobs created by 2030 in our pathway thanks to new activities and investment in clean energy. Spending on more efficient appliances, electric and fuel cell vehicles, and building retrofits and energy-efficient construction would require a further 16 million workers. But these opportunities are often in different locations, skill sets and sectors than the jobs that will be lost as fossil fuels decline. In our pathway, around 5 million jobs are lost. Most of those jobs are located close to fossil fuel resources, and many are well paid, meaning structural changes can cause shocks for communities with impacts that persist over time. This requires careful policy attention to address the employment losses. It will be vital to minimise hardships associated with these disruptions, such as by retraining workers, locating new clean energy facilities in heavily affected areas wherever possible, and providing regional aid.

Global employment in energy supply in the Net Zero Scenario, 2019-2030

An energy sector dominated by renewables.

In the net zero pathway, global energy demand in 2050 is around 8% smaller than today, but it serves an economy more than twice as big and a population with 2 billion more people. More efficient use of energy, resource efficiency and behavioural changes combine to offset increases in demand for energy services as the world economy grows and access to energy is extended to all.

Instead of fossil fuels, the energy sector is based largely on renewable energy. Two-thirds of total energy supply in 2050 is from wind, solar, bioenergy, geothermal and hydro energy. Solar becomes the largest source, accounting for one-fifth of energy supplies. Solar PV capacity increases 20-fold between now and 2050, and wind power 11-fold.

Net zero means a huge decline in the use of fossil fuels. They fall from almost four-fifths of total energy supply today to slightly over one-fifth by 2050. Fossil fuels that remain in 2050 are used in goods where the carbon is embodied in the product such as plastics, in facilities fitted with CCUS, and in sectors where low-emissions technology options are scarce.

Electricity accounts for almost 50% of total energy consumption in 2050. It plays a key role across all sectors – from transport and buildings to industry – and is essential to produce low-emissions fuels such as hydrogen. To achieve this, total electricity generation increases over two-and-a-half-times between today and 2050. At the same time, no additional new final investment decisions should be taken for new unabated coal plants, the least efficient coal plants are phased out by 2030, and the remaining coal plants still in use by 2040 are retrofitted. By 2050, almost 90% of electricity generation comes from renewable sources, with wind and solar PV together accounting for nearly 70%. Most of the remainder comes from nuclear.    

Emissions from industry, transport and buildings take longer to reduce. Cutting industry emissions by 95% by 2050 involves major efforts to build new infrastructure. After rapid innovation progress through R&D, demonstration and initial deployment between now and 2030 to bring new clean technologies to market, the world then has to put them into action. Every month from 2030 onwards, ten heavy industrial plants are equipped with CCUS, three new hydrogen-based industrial plants are built, and 2 GW of electrolyser capacity are added at industrial sites. Policies that end sales of new internal combustion engine cars by 2035 and boost electrification underpin the massive reduction in transport emissions. In 2050, cars on the road worldwide run on electricity or fuel cells. Low-emissions fuels are essential where energy needs cannot easily or economically be met by electricity. For example, aviation relies largely on biofuels and synthetic fuels, and ammonia is vital for shipping. In buildings, bans on new fossil fuel boilers need to start being introduced globally in 2025, driving up sales of electric heat pumps. Most old buildings and all new ones comply with zero-carbon-ready building energy codes. 1

Priority action: Set near-term milestones to get on track for long-term targets

Governments need to provide credible step-by-step plans to reach their net zero goals, building confidence among investors, industry, citizens and other countries.

Governments must put in place long-term policy frameworks to allow all branches of government and stakeholders to plan for change and facilitate an orderly transition. Long-term national low-emissions strategies, called for by the Paris Agreement, can set out a vision for national transitions, as this report has done on a global level. These long-term objectives need to be linked to measurable short-term targets and policies. Our pathway details more than 400 sectoral and technology milestones to guide the global journey to net zero by 2050.  

There is no need for investment in new fossil fuel supply in our net zero pathway

Beyond projects already committed as of 2021, there are no new oil and gas fields approved for development in our pathway, and no new coal mines or mine extensions are required. The unwavering policy focus on climate change in the net zero pathway results in a sharp decline in fossil fuel demand, meaning that the focus for oil and gas producers switches entirely to output – and emissions reductions – from the operation of existing assets. Unabated coal demand declines by 98% to just less than 1% of total energy use in 2050. Gas demand declines by 55% to 1 750 billion cubic metres and oil declines by 75% to 24 million barrels per day (mb/d), from around 90 mb/d in 2020.

Clean electricity generation, network infrastructure and end-use sectors are key areas for increased investment. Enabling infrastructure and technologies are vital for transforming the energy system. Annual investment in transmission and distribution grids expands from USD 260 billion today to USD 820 billion in 2030. The number of public charging points for EVs rises from around 1 million today to 40 million in 2030, requiring annual investment of almost USD 90 billion in 2030. Annual battery production for EVs leaps from 160 gigawatt-hours (GWh) today to 6 600 GWh in 2030 – the equivalent of adding almost 20 gigafactories 2  each year for the next ten years. And the required roll-out of hydrogen and CCUS after 2030 means laying the groundwork now: annual investment in CO 2 pipelines and hydrogen-enabling infrastructure increases from USD 1 billion today to around USD 40 billion in 2030.

Priority action: Drive a historic surge in clean energy investment

Policies need to be designed to send market signals that unlock new business models and mobilise private spending, especially in emerging economies.

Accelerated delivery of international public finance will be critical to energy transitions, especially in developing economies, but ultimately the private sector will need to finance most of the extra investment required. Mobilising the capital for large-scale infrastructure calls for closer co operation between developers, investors, public financial institutions and governments. Reducing risks for investors will be essential to ensure successful and affordable clean energy transitions. Many emerging market and developing economies, which rely mainly on public funding for new energy projects and industrial facilities, will need to reform their policy and regulatory frameworks to attract more private finance. International flows of long-term capital to these economies will be needed to support the development of both existing and emerging clean energy technologies.

Clean energy investment in the net zero pathway, 2016-2050

An unparalleled clean energy investment boom lifts global economic growth.

Total annual energy investment surges to USD 5 trillion by 2030, adding an extra 0.4 percentage point a year to annual global GDP growth, based on our joint analysis with the International Monetary Fund. This unparalleled increase – with investment in clean energy and energy infrastructure more than tripling already by 2030 – brings significant economic benefits as the world emerges from the Covid-19 crisis. The jump in private and government spending creates millions of jobs in clean energy, including energy efficiency, as well as in the engineering, manufacturing and construction industries. All of this puts global GDP 4% higher in 2030 than it would be based on current trends.

Governments have a key role in enabling investment-led growth and ensuring that the benefits are shared by all. There are large differences in macroeconomic impacts between regions. But government investment and public policies are essential to attract large amounts of private capital and to help offset the declines in fossil fuel income that many countries will experience. The major innovation efforts needed to bring new clean energy technologies to market could boost productivity and create entirely new industries, providing opportunities to locate them in areas that see job losses in incumbent industries. Improvements in air quality provide major health benefits, with 2 million fewer premature deaths globally from air pollution in 2030 than today in our net zero pathway. Achieving universal energy access by 2030 would provide a major boost to well-being and productivity in developing economies.

New energy security concerns emerge, and old ones remain

The contraction of oil and natural gas production will have far-reaching implications for all the countries and companies that produce these fuels. No new oil and natural gas fields are needed in our pathway, and oil and natural gas supplies become increasingly concentrated in a small number of low-cost producers. For oil, the OPEC share of a much-reduced global oil supply increases from around 37% in recent years to 52% in 2050, a level higher than at any point in the history of oil markets. Yet annual per capita income from oil and natural gas in producer economies falls by about 75%, from USD 1 800 in recent years to USD 450 by the 2030s, which could have knock-on societal effects. Structural reforms and new sources of revenue are needed, even though these are unlikely to compensate fully for the drop in oil and gas income. While traditional supply activities decline, the expertise of the oil and natural gas industry fits well with technologies such as hydrogen, CCUS and offshore wind that are needed to tackle emissions in sectors where reductions are likely to be most challenging.

The energy transition requires substantial quantities of critical minerals, and their supply emerges as a significant growth area. The total market size of critical minerals like copper, cobalt, manganese and various rare earth metals grows almost sevenfold between 2020 and 2030 in the net zero pathway. Revenues from those minerals are larger than revenues from coal well before 2030. This creates substantial new opportunities for mining companies. It also creates new energy security concerns, including price volatility and additional costs for transitions, if supply cannot keep up with burgeoning demand.

The rapid electrification of all sectors makes electricity even more central to energy security around the world than it is today. Electricity system flexibility – needed to balance wind and solar with evolving demand patterns – quadruples by 2050 even as retirements of fossil fuel capacity reduce conventional sources of flexibility. The transition calls for major increases in all sources of flexibility: batteries, demand response and low-carbon flexible power plants, supported by smarter and more digital electricity networks. The resilience of electricity systems to cyberattacks and other emerging threats needs to be enhanced.

Priority action: Address emerging energy security risks now

Ensuring uninterrupted and reliable supplies of energy and critical energy-related commodities at affordable prices will only rise in importance on the way to net zero.

The focus of energy security will evolve as reliance on renewable electricity grows and the role of oil and gas diminishes. Potential vulnerabilities from the increasing importance of electricity include the variability of supply and cybersecurity risks. Governments need to create markets for investment in batteries, digital solutions and electricity grids that reward flexibility and enable adequate and reliable supplies of electricity. The growing dependence on critical minerals required for key clean energy technologies calls for new international mechanisms to ensure both the timely availability of supplies and sustainable production. At the same time, traditional energy security concerns will not disappear, as oil production will become more concentrated.

Critical minerals demand in the net zero pathway, 2020-2050

Oil supply in the net zero pathway, 2020-2050, international co-operation is pivotal for achieving net zero emissions by 2050.

Making net zero emissions a reality hinges on a singular, unwavering focus from all governments – working together with one another, and with businesses, investors and citizens. All stakeholders need to play their part. The wide-ranging measures adopted by governments at all levels in the net zero pathway help to frame, influence and incentivise the purchase by consumers and investment by businesses. This includes how energy companies invest in new ways of producing and supplying energy services, how businesses invest in equipment, and how consumers cool and heat their homes, power their devices and travel.

Underpinning all these changes are policy decisions made by governments. Devising cost-effective national and regional net zero roadmaps demands co-operation among all parts of government that breaks down silos and integrates energy into every country’s policy making on finance, labour, taxation, transport and industry. Energy or environment ministries alone cannot carry out the policy actions needed to reach net zero by 2050.

Changes in energy consumption result in a significant decline in fossil fuel tax revenues. In many countries today, taxes on diesel, gasoline and other fossil fuel consumption are an important source of public revenues, providing as much as 10% in some cases. In the net zero pathway, tax revenue from oil and gas retail sales falls by about 40% between 2020 and 2030. Managing this decline will require long-term fiscal planning and budget reforms.

The net zero pathway relies on unprecedented international co-operation among governments, especially on innovation and investment. The IEA stands ready to support governments in preparing national and regional net zero roadmaps, to provide guidance and assistance in implementing them, and to promote international co-operation to accelerate the energy transition worldwide. 

Priority action: Take international co-operation to new heights

This is not simply a matter of all governments seeking to bring their national emissions to net zero – it means tackling global challenges through co-ordinated actions.

Governments must work together in an effective and mutually beneficial manner to implement coherent measures that cross borders. This includes carefully managing domestic job creation and local commercial advantages with the collective global need for clean energy technology deployment. Accelerating innovation, developing international standards and co-ordinating to scale up clean technologies needs to be done in a way that links national markets. Co-operation must recognise differences in the stages of development of different countries and the varying situations of different parts of society. For many rich countries, achieving net zero emissions will be more difficult and costly without international co-operation. For many developing countries, the pathway to net zero without international assistance is not clear. Technical and financial support is needed to ensure deployment of key technologies and infrastructure. Without greater international co-operation, global CO 2 emissions will not fall to net zero by 2050. 

Global energy-related CO2 emissions in the net zero pathway and Low International Cooperation Case, 2010-2090

A zero-carbon-ready building is highly energy efficient and either uses renewable energy directly or uses an energy supply that will be fully decarbonised by 2050, such as electricity or district heat.

Battery gigafactory capacity assumption = 35 gigawatt-hours per year.

Reference 1

Reference 2, related net zero reports, related files.

• English Download "English"
• Italian Download "Italian"

Executive summaries

• Chinese Download "Chinese"
• Polish Download "Polish"

Full report translations

• Launch presentation Download "Launch presentation"
• The need for net zero demonstration projects Download "The need for net zero demonstration projects"

Additional downloads

Cite report.

IEA (2021), Net Zero by 2050 , IEA, Paris https://www.iea.org/reports/net-zero-by-2050, Licence: CC BY 4.0

Share this report

• Share on Twitter Twitter
• Share on Facebook Facebook
• Share on LinkedIn LinkedIn
• Share on Email Email
• Share on Print Print

Subscription successful

Thank you for subscribing. You can unsubscribe at any time by clicking the link at the bottom of any IEA newsletter.