Scientists warn less than four years remain to limit warming

The window to limit global warming to 1.5°C is closing rapidly, with scientists estimating that less than four years of carbon budget remain at current emission rates. While renewable energy adoption and electric vehicles are altering emissions trajectories, a new assessment indicates that total atmospheric carbon dioxide output continues to rise due to land-use changes and insufficient clean energy acceleration.

Fossil Fuel Emission Projections

Global fossil fuel emissions are forecast to decrease by 0.4% in 2026, reaching 38.2 billion metric tons (42.1 billion U.S. tons). This marginal decline is attributed partly to expanding clean energy infrastructure and supply disruptions stemming from the Iran conflict. However, rising emissions from deforestation and other land-use modifications are expected to push total global CO2 emissions to 43.3 billion metric tons (47.7 billion U.S. tons), an increase from 42.8 billion metric tons recorded in 2025.

Oil consumption accounts for the majority of the projected reduction in fossil fuel emissions, with global CO2 output from oil expected to drop by 1.9%. This decline reflects the energy shock associated with the Iran conflict, which has constrained supplies and driven up prices. Natural gas emissions are projected to fall by 0.3%, while coal emissions may rise by 0.6%. International aviation and shipping emissions are each expected to decrease by 1%, with reduced activity in the Middle East contributing specifically to the aviation sector's decline.

Structural vs. Temporary Reductions

Professor Pierre Friedlingstein, director of the Global Carbon Budget Office at the University of Exeter and lead author of the study, cautioned against interpreting these figures as sustainable progress. “A decline in fossil CO2 emissions is encouraging, but a reduction driven partly by geopolitical shocks is not a sustainable climate solution,” Friedlingstein stated. He emphasized that the long-term solution requires rapid deployment of clean energy technologies, noting that further acceleration is necessary for global emissions to peak and enter a sustained decline.

Glen Peters, Research Professor at the CICERO Center for International Climate Research, reinforced this perspective, distinguishing between temporary fluctuations and structural shifts. “A drop in emissions in one year is not a peak unless it is driven by structural change,” Peters said. He acknowledged that accelerated deployment of solar, wind, batteries, and electric vehicles is reducing emissions in dozens of countries and slowing growth in many others, but concluded that these changes are currently insufficient to lock in a global peak.

Clean Energy’s Impact on Demand

Solar power, wind energy, and electric vehicles are increasingly limiting emissions despite rising global energy demand. According to the assessment, these technologies are meeting or avoiding approximately two-thirds of the increase in energy demand. Solar and wind generation alone are projected to prevent 4.6 billion metric tons (5.1 billion U.S. tons) of CO2 emissions in 2026, a significant jump from 4.1 billion metric tons in 2025 and just 0.28 billion metric tons in 2010.

China plays a central role in this transformation. Although the country produces roughly 32% of global fossil fuel emissions, it accounts for half of the emissions avoided worldwide through renewable energy and electric vehicle adoption. China’s emissions are projected to decline by 0.9% in 2026, aided by lower oil consumption and continued expansion of renewable electricity. Coal emissions in China are expected to rise slightly by 0.3%. Additionally, China leads the world in carbon uptake from reforestation and afforestation efforts.

Professor Corinne Le Quéré, Royal Society Research Professor at the University of East Anglia’s School of Environmental Sciences, highlighted the tangible impact of these technologies. “Clean technologies are making a real difference in reducing global emissions. Solar and wind power and electric vehicles are expanding rapidly, led by China,” Le Quéré said. She noted that countries on every continent are decreasing emissions while growing their economies, suggesting that further acceleration could turn the tide on global emissions within a few years.

Regional Emission Trends

Emissions trends vary significantly across major economies. The United States is projected to see a 1.3% decline, primarily due to falling coal consumption following a 2025 increase driven by high natural gas prices and cold weather. The European Union is expected to record a 1.5% reduction, while Japan’s emissions could decrease by 1%. In contrast, India is moving in the opposite direction, with emissions projected to rise by 4.4%, exceeding its average annual growth rate of 3.5% over the past decade. Emissions across the rest of the world are expected to decrease by 0.7%, largely due to reduced oil consumption.

An accompanying analysis, currently in press in a separate peer-reviewed journal, identifies a broader decoupling of economic growth from carbon emissions. In 59 countries, emissions were lower in 2025 than in 2019, before the COVID-19 pandemic, even as their economies expanded. Emissions growth has also slowed in regions where total emissions continue to rise, including China, India, and other emerging economies.

Land Use and Carbon Sinks

The decline in fossil fuel emissions is being offset by increasing carbon releases from land-use change, such as deforestation. These emissions are projected to reach 5.1 billion metric tons (5.6 billion U.S. tons) in 2026. The increase is linked partly to peat fires and forest degradation in Southeast Asia, where drier conditions associated with El Niño have heightened fire risks. Nearly all peat fires are ignited by human activities.

Natural ecosystems play a critical role in regulating atmospheric CO2 levels. Forests, soils, and oceans absorb substantial amounts of carbon, acting as natural sinks. The Global Carbon Budget reports that land-based carbon absorption recovered after weakening sharply during the 2023 and 2024 El Niño event. However, the powerful El Niño developing in 2026 is expected to affect this natural carbon uptake over the coming year.

Remaining Carbon Budget

The latest assessment estimates that only 150 billion metric tons (165 billion U.S. tons) of CO2 can be emitted before cumulative emissions reach the level associated with 1.5°C (2.7°F) of global warming above preindustrial levels. At current emission rates, this remaining carbon budget amounts to less than four years. Atmospheric CO2 concentrations are projected to reach 427.7 parts per million in 2026, approximately 54% above preindustrial levels.

Removing carbon dioxide from the atmosphere remains a significant challenge. Permanent deforestation released an average of approximately 3.8 billion metric tons (4.2 billion U.S. tons) of CO2 annually between 2016 and 2025. Reforestation and afforestation offset roughly half of those emissions. China, the European Union, and the United States account for the largest combined removals through forest restoration and expansion, while deforestation outweighs these gains in countries including Brazil, Russia, and Indonesia. Technologies designed to remove atmospheric CO2 remain limited, currently capturing less than the amount released by fossil fuels in just 30 minutes.

Professor Julia Pongratz of Ludwig-Maximilian-University Munich stressed the need for comprehensive action. “Alongside reducing emissions, we need to scale up CO2 removal to reach greenhouse gas neutrality,” Pongratz said. She noted that while afforestation and reforestation already remove substantial amounts of CO2, these gains are still more than offset by emissions from deforestation, and novel carbon removal remains very limited.

Path to Sustained Peak

Despite continued increases in total emissions, the long-term growth rate has slowed substantially. Global CO2 emissions rose by an average of 0.3% annually over the past decade, compared with 1.7% annually during the preceding decade. The accompanying analysis projects that between now and the end of 2028, additional solar and wind generation and electric vehicles could prevent emissions equivalent to 64% to 79% of those associated with rising energy demand. Electric vehicles are becoming increasingly influential, although only about 10% of the global passenger car fleet was electrified in 2025 (or 6% excluding hybrids).

The researchers conclude that continued deployment of clean technologies could bring the first sustained global decline in CO2 emissions within reach. Achieving this outcome depends on maintaining and accelerating their expansion rather than relying on temporary reductions caused by economic or geopolitical disruptions. As the authors write, “If further acceleration of clean technology deployment can be supported through time, a sustained peak and decline in global CO2 emissions could be a few years away.”

Reference: “Global Carbon Budget 2026” by Pierre Friedlingstein, Michael O’Sullivan, Robbie M. Andrew, Judith Hauck, Matthew W. Jones, Peter Landschützer, Corinne Le Quéré, Hongmei Li, Ingrid T. Luijkx, Are Olsen, Glen P. Peters, Wouter Peters, Julia Pongratz, Clemens Schwingshackl, Stephen Sitch, Josep G. Canadell, Philippe Ciais, Kjetil Aas, Simone R. Alin, Vivek Arora, Nicholas R. Bates, Kimberly Bedard, David Martin Belda, Nicolas Bellouin, Alice Benoit-Cattin, Carla F. Berghoff, Sarah Berthet, Laurent Bopp, Ida Bagus Mandhara Brasika, Eleanor Burke, Leon Casse, Matthew A. Chamberlain, Frédéric Chevallier, Louise P. Chini, Margot Cronin, Susan E. Curless, Tim DeVries, Tobias Ehmen, Matthew P. Enright, Kazutaka Enyo, Michael Erb, Wiley Evans, Amanda R. Fay, Ben Felzer, Daniel J. Ford, Adrianna Foster, Filippa Fransner, Agneta Fransson, Andrew Friedman, Thomas Gasser, Marion Gehlen, Thanos Gkritzalis, Giacomo Grassi, Luke Gregor, Nicolas Gruber, Özgür Gürses, Wensu Hao, Kirsty Harrington, Jens Heinke, George C. Hurtt, Tatiana Ilyina, Akihiko Ito, Andrew R. Jacobson, Atul K. Jain, Rajesh Janardanan, Tereza Jarníková, Annika Jersild, Fei Jiang, Zhe Jin, Linus Kamb, Etsushi Kato, Ralph F. Keeling, Kees Klein Goldewijk, Jürgen Knauer, Jan Ivar Korsbakken, Taro Kunimitsu, Xin Lan, Vladimir Lapin, Siv K. Lauvset, Simone Le Chevère, Woo-Sung Lee, Enhui Liao, Junjie Liu, Zhu Liu, Sebastiaan Luyssaert, Lei Ma, Suman Maity, Gregg Marland, Patrick C. McGuire, Nicolas Metzl, Juliette Mignot, Natalie M. Monacci, Eric J. Morgan, Jens D. Müller, David R. Munro, Miaki Muramatsu, Shin-Ichiro Nakaoka, Craig Neill, Tobias Nützel, Léa Olivier, Timothy Osborn, Xosé A. Padín, Paul I. Palmer, Sudhanshu Pandey, Denis Pierrot, Ben Poulter, Zhangcai Qin, Yumou Qiu, Gregor Rehder, Laure Resplandy, Christian Rödenbeck, Alizée Roobaert, Thais M. Rosan, Simone Rossi, Jörg Schwinger, Gereon Seeberg, Roland Séférian, Elisabeth H. Shadwick, Ingunn Skjelvan, Karolina Slominska-Durdasiak, T. Luke Smallman, Mohanan G Sreeush, Qing Sun, Adrienne J. Sutton, Colm Sweeney, Shintaro Takao, Hiroaki Tatebe, Jens Terhaar, Hanqin Tian, Bronte Tilbrook, Takahiro Toyoda, Joaquin A. Triñanes, Francesco Tubiello, Guido R. van der Werf, Auke van der Woude, Sebastiaan J. van de Velde, Anthony P. Walker, Rik Wanninkhof, Xiaojuan Yang, Wenping Yuan, Xu Yue, Jiye Zeng, Ning Zheng and Bo Zheng, 10 November 2026, Earth System Science Data Discussions. DOI: 10.5194/essd-2026-895