Paris accord threshold could be breached in 4 years as warning accelerates: Analysis

NEW DELHI: Earth's climate system is accumulating heat at an accelerating rate as human activity pushed global warming to 1.37 degrees Celsius last year, with the figure projected to surpass the Paris Agreement threshold of 1.5 degrees in about four years, strong and consistent evidence shows, researchers have said.

Record-high greenhouse gas (GHG) levels, combined with a continued drop in sulphur aerosols – thereby unmasking a part of the GHGs' warming effect – are driving human-induced warming, which remains at an all-time high of around 0.27 degrees Celsius per decade, an international team of more than 70 scientists from 56 institutions across 17 countries, including the UK, the US, India and in Europe, said.

There is evidence that carbon dioxide emission growth is slowing, but society needs to massively increase decarbonisation efforts during this critical decade, the researchers said.

They added that the rate at which heat is accumulating in the Earth system suggests high levels of future warming. The team has published findings from the fourth edition of the Indicators of Global Climate Change (IGCC) report in the Earth System Science Data journal.

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," Forster said.

Greenhouse gas emissions across the world were found to be at an all-time high, reaching 56.8 billion tonnes (gigatonnes) of carbon dioxide equivalent emissions (CO2e) in 2024, mainly from the burning of fossil fuels.

The analysis, which looked at over 40 global datasets, also estimated that the remaining carbon budget -- the amount of carbon dioxide that can still be emitted if global warming is to be kept below 1.5 degrees Celsius -- is 130 gigatonnes from the start of 2026.

At current levels of carbon dioxide emissions, the central estimate will be exhausted in around three years, the researchers said.

"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 authors wrote.

The year 2025 was the third warmest on record, consistent with the level of human-caused warming the world has experienced, and natural variability in the climate system had a limited effect on global mean temperatures last year, they 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," author Samantha Burgess, strategic lead for climate in the Copernicus Climate Change Service (C3S) at the European Centre for Medium-Range Weather Forecasts (ECMWF), said.

The fourth edition newly included an indicator: the number of days experiencing marine heatwaves. Globally, 2025 alone experienced 65 days of marine heatwaves.

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."

"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," Lee said.

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, highlighting the need for society to massively increase decarbonisation efforts during this critical decade, the team said.