The Path to Limiting Long-Term Warming
Global temperatures are expected to rise above 1.5°C compared with pre-industrial levels. A new climate analysis finds that the world could still return to that limit by 2100, but only if countries make deep cuts in greenhouse gas emissions and remove large amounts of carbon dioxide from the air.
A Narrow Path Back to 1.5°C
In the least severe pathway studied, warming reaches a high point of about 1.7°C to 1.8°C around the middle of the century, then falls to 1.5°C or lower by 2100. There is about a one-in-two chance of reaching that outcome.
Getting onto this path would require global greenhouse gas emissions to fall by 18% by 2030, 45% by 2035, and 69% by 2040, compared with 2025 levels. That means average yearly cuts of about 5.7% from 2025 to 2035.
Current national climate pledges fall far short. If countries fully meet them, emissions would decline by only 5% to 8% by 2030 and 11% to 15% by 2035, compared with 2025 levels. The needed yearly cuts are also steeper than those in earlier climate pathways, which called for reductions of about 5% per year.
Going above 1.5°C would not make a return impossible, but every added year and fraction of a degree increases the danger from events such as floods, heat waves, and wildfires. At today’s level of carbon dioxide emissions, every five years would add about 0.1°C to peak warming.
Current Projections Remain High
If today’s policies stay in place, warming could reach 2.8°C during this century and continue rising afterward. If countries meet their climate pledges and maintain similar efforts, warming could be held to 2.6°C. Even if every pledge and additional net-zero goal is met, the estimate is still 2.1°C.
These outlooks are worse than earlier estimates. The changes reflect the United States leaving the Paris climate agreement and updated calculations of past emissions. New national pledges have made little difference to the projections.
Holding the peak below 1.7°C to 1.8°C will become impossible without fast action. The lowest-overshoot pathway would also depend on removing about 320 billion tonnes of carbon dioxide from the atmosphere and storing it permanently over the century. That is roughly equal to eight years of global carbon dioxide emissions at 2024 levels. The ability to remove and store so much carbon remains uncertain because of economic, social, and technical challenges.
Clean Energy and Climate Policies Can Help
There are signs that action can work. Since countries adopted the Paris Agreement, renewable energy has expanded, coal and oil supplies have grown more slowly than expected, and climate policies have reduced emissions in many places.
More than 220 evaluations of climate policies offer evidence of progress. Policies in the electricity sector cut emissions by an average of 9%. Economic tools, including carbon taxes and programs that limit and trade emissions, reduced emissions by 5% to 13% across the sectors and periods studied.
These results are not yet widespread enough. They have been concentrated in certain countries, industries, and time periods. Reaching the least severe warming pathway would require countries to repeat and expand successful efforts, then keep them in place.
More Ambitious Goals Are Needed
Countries have already agreed to expand renewable energy, improve energy efficiency, shift away from fossil fuels, reduce emissions other than carbon dioxide, and stop deforestation. But recent trends in several areas are moving in the wrong direction. This includes emissions from energy, road transport, and methane.
Some emissions may level off by 2030 under current policies, but none are expected to fall quickly enough to limit how high temperatures rise or how long they stay above 1.5°C. Future global climate goals could strengthen earlier commitments and set clearer targets for 2035 and 2040.
- By 2035, renewable electricity capacity would need to be at least three times its 2025 level. By 2040, it would need to reach at least 4.5 times that level.
- Energy use per unit of economic output would need to improve by at least 30% by 2035 and 40% by 2040, compared with 2025.
- By 2035, the global shares of coal, oil, and gas in total energy supply would need to fall by at least 55%, 15%, and 5%, respectively. By 2040, the cuts would need to reach at least 75%, 30%, and 35%.
- Coal-fired electricity generation would need to drop by at least 75% by 2035 and be almost entirely phased out around the world by 2040.
- Methane emissions would need to fall by at least 25% by 2035 and 40% by 2040.
Renewable energy growth offers a reason for confidence. Since the Paris Agreement was adopted, global renewable electricity capacity has increased three times faster than expected. Solar power capacity has grown seven times faster. Continuing that growth, with stronger policies, could help triple renewable energy capacity by 2030 and raise wind and solar power to levels needed for the least severe warming pathway.