The Earth is accumulating heat at an accelerating rate. Global warming reached 1.37°C in 2025

Strong and consistent evidence shows that the entire climate system is continuing to heat, driving rapid global warming. Human activities pushed global warming to 1.37°C in 2025, and its level is projected to surpass 1.5°C in about four years. Crucially, the rate at which heat is accumulating in the Earth system suggests high levels of future warming. These are some of the key findings from the latest Indicators of Global Climate Change (IGCC) report, published today in Earth System Science Data.

An international team of more than 70 scientists, including IPCC Lead Authors, Contributing Authors, and Chapter Scientists, from 56 institutions across 17 countries contributed to this year’s IGCC study. 

Prof. Piers Forster, Director of the Priestley Centre for Climate Futures at the University of Leeds and lead author, said:

A key indicator is the Earth's energy imbalance, which measures how fast heat is accumulating in the climate system, and provides a crucial measure of the pace of climate change. Without human influence, it should be close to zero, but it has been growing since the 1970s and is now at a record high, doubling in recent decades.

This year’s update also finds that global greenhouse gas (GHG) emissions are at an all-time high, reaching 56.8 billion tonnes (gigatonnes or Gt) of carbon dioxide equivalent emissions (CO2e) in 2024, mainly from the burning of fossil fuels. 

Warming driven by human activities

Other findings show that 2025 was the third warmest year on record, consistent with the level of human-caused warming the world has experienced, and that natural variability in the climate system had a limited effect on global mean temperatures last year.

Dr. Samantha Burgess, Strategic Lead for Climate in the Copernicus Climate Change Service (C3S) at ECMWF, said: “Our study demonstrates that nearly all of the warming over the last decade is driven by human activities. The impacts on livelihoods and ecosystems are already being felt worldwide, and will accelerate as temperatures continue to increase.”

The rate of human-induced warming remains at the all-time high of around 0.27°C per decade, driven primarily by record-high greenhouse gas levels, combined with the continued fall in sulfur dioxide (SO2) emissions partly resulting from measures to tackle air pollution. While CO2 emissions remain the dominant driver of global warming, the reduction in sulfur aerosols is unmasking part of the warming effect of GHGs.

Dr. Matt Palmer, Science Fellow at the UK Met Office, said: “It comes down to a simple principle: we are emitting more greenhouse gases than ever before, causing rising greenhouse gas levels which are trapping more and more heat in the atmosphere and pushing the world out of balance.” 

Earth's energy imbalance is growing

Dr. Karina Von Schuckmann, Senior Advisor, Ocean Science for Policy at Mercator Ocean International, added: “The Earth’s energy imbalance is growing fast, driving changes in every component of the climate system, including ocean and continental warming, permafrost thawing, ice loss, and sea level rise.”

Consistent with the increase in the Earth’s energy imbalance, the rate of global sea level rise is accelerating due to higher ocean temperatures and melting of land-based ice. Dr. Aimée Slangen, Research Leader at the Royal Netherlands Institute for Sea Research (NIOZ), said: “In 2025, global sea level rise reached a new record of 23 cm of rise since 1901, at a rate of around 1.8 mm per year, and this rate is speeding up fast. This might sound small, but even this level of change is increasing coastal flooding in low-lying areas around the world, harming livelihoods and ecosystems.”

New indicator - marine heatwaves

Changes in the occurrence and intensity of climate and weather extremes provide supporting evidence of widespread changes in the climate system. A newly included indicator, the number of days experiencing marine heatwaves, found that, globally, 2025 alone experienced 65 days of marine heatwaves. 

Prof. June-Yi Lee, Professor at Research Center for Climate Sciences, Pusan National University, highlighted: “Marine heatwaves are becoming more frequent, consistent with the ongoing warming of the ocean surface. The number of days experiencing marine heatwaves has more than tripled globally between 1991 and 2025. These events harm marine ecosystems while threatening food production, economies, and coastal protection. They also disrupt ocean-atmosphere carbon exchange, ocean acidity and oxygen levels, and can intensify extreme weather on land.”   

The remaining carbon budget – the total amount of carbon dioxide that can still be emitted if we want to keep global warming below 1.5°C – is meanwhile estimated to be 130 Gt CO2 from the start of 2026. This central estimate will be exhausted in around three years at current levels of CO2 emissions.

Despite GHG emissions not increasing as rapidly as in the 2000s, this year’s findings continue to show how far and how fast the climate is changing due to human activity, highlighting the need for society to massively increase decarbonisation efforts during this critical decade.

A comprehensive picture

Preserving and maintaining the global datasets that are crucial for providing the most up-to-date, accurate, comprehensive information for evidence-based decision making will meanwhile be critical to our ability to detect these changes in the future.

Dr. Chris Smith, Senior Research Scholar at the International Institute for Applied Systems Analysis, added: “This year’s edition of IGCC has involved over 40 global datasets, many of which are now threatened by funding decisions. We need concerted international action and coordination to ensure the continuity of observations of the climate. Without this, future assessments will be much more difficult at a time when urgent climate action is needed.”

Other key findings:

• Human-induced warming reached 1.37°C in 2025 relative to 1850-1900, increasing at a rate of around 0.27°C per decade (2016-2025). If current emissions continue, we can expect to reach 1.5°C around 2030. 
• Atmospheric GHG concentrations reached 425.6 parts per million (ppm) for carbon dioxide (CO2), 1936.3 parts per billion (ppb) for methane (CH4) and 339.4 ppb for nitrous oxide (N2O) in 2025. Concentrations of all three major GHGs have increased since 2019, with CO2 increasing by 15.6 ppm, CH4 by 70.0 ppb, and N2O by 7.2 ppb between 2019 and 2025.
• The decade 2016-2025 was 0.32°C warmer than the previous decade (2006–2015), amplified by the exceptionally warm years in 2023 and 2024 to give a larger than typical warming rate compared to the previous few decades. 
• While global land precipitation has shown considerable variability over recent years and decades, all datasets indicate its increase relative to 2024. In 2025, there was enhanced rainfall over Asia and the Maritime Continent, likely linked to La Niña conditions, as well as over Siberia and southern Africa. The pronounced rainfall deficit over central South America during 2023–2024 was markedly reduced in 2025. In contrast, wet conditions have persisted across the Arctic and much of Siberia from 2023 to 2025. 
• The rapid warming over the last few decades has resulted in record extreme temperatures over land. Land average maximum temperatures for any single day in a year reached 1.92°C over the last decade (2016-2025), an increase of 0.49°C compared to 2006-2015.   

For media enquiries, please contact: [email protected]

Read the research paper: Indicators of Global Climate Change 2025: annual update of key indicators of the state of the climate system and human influence