U.S. nonprofit says '99 percent' chance 2026 will be one of seven hottest years on record

Even as governments around the world clean up the air by cracking down on pollution, the planet is heating up faster, scientists say, with new forecasts showing that this year is almost certain to rank among the hottest ever recorded.

People seek shade to avoid the sun at Gwanghwamun Square in Jongno District, central Seoul, on Aug. 5, 2025, amid a heat wave. [YONHAP]

Even as governments around the world clean up the air by cracking down on pollution, the planet is heating up faster, scientists say, with new forecasts showing that this year is almost certain to rank among the hottest ever recorded.

In Korea, rising temperatures are expected to intensify heat waves and extreme weather, with analysts warning the effects of global warming will “directly affect” public safety and the economy.

The U.S.-based nonprofit climate and weather analysis group Berkeley Earth said on Wednesday that there is a 99 percent chance global average temperatures in 2026 will rank among the seven highest on record. It projected a 51 percent probability the year will place fourth, with a 21 percent chance of ranking second.

Last year already ranked as the third warmest on record compared to the preindustrial average from 1850 to 1900, and similar conditions are likely to persist this year, Berkeley Earth said.

The main driver of rising global temperatures remains the buildup of greenhouse gases such as carbon dioxide and methane. Although the rate of increase in carbon dioxide emissions has slowed, overall emissions continue to rise.

Global emissions in 2025 increased 1.1 percent from a year earlier to a record high, while atmospheric concentrations reached an unprecedented 425 to 426 parts per million.

Higher concentrations of greenhouse gases trap heat within the Earth system. They allow incoming solar radiation to pass through the atmosphere but prevent heat radiated from the Earth’s surface from escaping into space, causing temperatures to rise over land and oceans.

Berkeley Earth scientists also point to a less intuitive factor contributing to warming: declining air pollution, or, in more technical terms, man-made sulfur aerosols.

Aerosols, which include fine particles such as dust and sulfates suspended in the air, worsen air quality but also reflect sunlight and promote cloud formation, creating a cooling effect.

Such pollution, in addition to reductions to low cloud cover, have played a significant role in recent warming, according to the institute.

Ship tracks are seen over waters in the northeastern Pacific Ocean near Alaska on March 4, 2009. The long, streak-like clouds formed around particles contained in ship exhaust, a phenomenon that studies have found declined by about 80 percent following regulations introduced in 2020 to limit sulfur content in ship fuel. [NASA]

As countries including China strengthen environmental regulations and reduce aerosol emissions, more solar energy is reaching the Earth’s surface.

One visible example is the decline of ship tracks, or narrow cloud formations that follow major shipping routes. After the International Maritime Organization imposed stricter limits on sulfur content in marine fuel in 2020, emissions of sulfate aerosols that act as cloud seeds fell by about 80 percent.

Berkeley Earth said the combined effects of rising greenhouse gas concentrations and declining aerosols make another year of intense heat likely, even as the cooling influence of La Nina weakens in the second half of the year.

“The extremely unusual values we are seeing in recent annual average temperatures cannot be explained by rising carbon dioxide levels alone,” said Yeh Sang-wook, a professor of marine convergence engineering at Hanyang University. “The role of other substances such as aerosols needs to be examined.”

The implications extend to the Korean Peninsula.

“Global temperature increases have entered a stage where they directly affect Korea’s economy and public safety,” said O Jae-ho, emeritus professor at Pukyong National University’s College of Environmental and Marine Science and Technology.

“Heat waves, droughts, heavy rainfall and wildfires are likely to become more frequent and more severe,” O added.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom. BY HEO JEONG-WON [kim.juyeon2@joongang.co.kr]