A new report by an international team of scientists reveals that Earth's climate system is accumulating heat at an accelerating rate. Human-induced global warming reached 1.37 degrees Celsius in 2025, and the Paris Agreement threshold of 1.5 degrees Celsius is projected to be surpassed in about four years, according to strong and consistent evidence.
Record-High Greenhouse Gas Levels
The study, published in the journal Earth System Science Data, involved over 70 scientists from 56 institutions across 17 countries, including the UK, the US, India, and Europe. It found that record-high greenhouse gas (GHG) levels, combined with a continued drop in sulphur aerosols—which unmask part of the warming effect of GHGs—are driving human-induced warming. This warming remains at an all-time high of around 0.27 degrees Celsius per decade.
Carbon Dioxide Emissions and Decarbonisation
While there is evidence that carbon dioxide emission growth is slowing, the researchers emphasize that society needs to massively increase decarbonisation efforts during this critical decade. The rate at which heat is accumulating in the Earth system suggests high levels of future warming.
Lead author Piers Forster, professor and director of the Priestley Centre for Climate Futures at the University of Leeds, UK, 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."
Greenhouse Gas Emissions at All-Time High
Greenhouse gas emissions across the world reached an all-time high of 56.8 billion tonnes (gigatonnes) of carbon dioxide equivalent emissions (CO2e) in 2024, mainly from the burning of fossil fuels. The analysis, which examined over 40 global datasets, also estimated that the remaining carbon budget—the amount of carbon dioxide that can still be emitted to keep global warming below 1.5 degrees Celsius—is 130 gigatonnes from the start of 2026. At current emission levels, this budget will be exhausted in around three years.
Human-Induced Warming and Natural Variability
The authors wrote, "Human-induced warming reached 1.37 degrees Celsius relative to 1850-1900 in the year 2025, increasing at a rate of 0.27 degrees Celsius per decade over 2016-2025." The year 2025 was the third warmest on record, consistent with the level of human-caused warming, and natural variability had a limited effect on global mean temperatures last year.
Co-author Samantha Burgess, strategic lead for climate at the Copernicus Climate Change Service (C3S) of the European Centre for Medium-Range Weather Forecasts (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."
Marine Heatwaves Increasing
The fourth edition of the report includes a new indicator: the number of days experiencing marine heatwaves. Globally, 2025 alone experienced 65 days of marine heatwaves. Co-author June-Yi Lee, professor at the Research Center for Climate Sciences, Pusan National University in the Republic of Korea, said, "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."
Lee added, "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."
Need for Urgent Action
Even though greenhouse gas emissions are not increasing as rapidly as in the 2000s, the findings show how far and how fast human activity is changing the climate. The team highlighted the need for society to massively increase decarbonisation efforts during this critical decade to avoid the worst impacts of climate change.
