Why global warming is accelerating — and what it means for the future

Global temperatures over the past three years have risen faster than expected, sparking a growing debate among scientists about whether climate change itself is accelerating — and how much time remains to limit its worst impacts.

Most researchers agree that global warming is speeding up. But some argue the pace is exceeding what climate models predicted, while others say the recent surge is largely due to natural variability that may ease in the coming years.

“This is really a question of how severe climate change will become,” said Zeke Hausfather of Berkeley Earth.

For decades, Earth warmed at about 0.18°C per decade, but that rate appears to have increased since the 2010s. The shift became more apparent when 2023 emerged as the hottest year on record, accompanied by devastating floods, cyclones and wildfires across multiple continents.

Why temperatures may be rising faster

A major explanation comes from research by James Hansen of Columbia University, who estimates warming has accelerated to around 0.32°C per decade since 2010.

His team links this to a “Faustian bargain” with aerosol pollution. For years, sulphur emissions from fossil fuels reflected sunlight and helped cool the planet. As countries cut this pollution — notably China and through global shipping rules enforced by the International Maritime Organization — that masking effect is fading.

“The atmosphere is cleaner, so more solar radiation is reaching Earth,” said Samantha Burgess of the EU’s Copernicus Climate Change Service.

This effect appeared to intensify when 2024 temperatures exceeded 1.5°C above pre-industrial levels for the first time, with extreme heatwaves and storms continuing into 2025.

The role of natural factors

Not all scientists agree that acceleration is as dramatic as some studies suggest.

Natural influences have also played a role, including:

• A peak in the Sun’s 11-year activity cycle

• A massive 2022 underwater volcanic eruption near Tonga that injected water vapour into the atmosphere

• A strong El Niño event in 2023–24, which temporarily boosts global temperatures

Michael Mann of University of Pennsylvania argues recent warming remains consistent with existing climate models and does not require new explanations.

A possible wild card: cloud feedback

Another concern is the role of clouds — one of the least understood elements in climate science.

Research led by Helge Goessling at the Alfred Wegener Institute suggests that declining low-level clouds may have contributed about 0.2°C of warming in 2023. If warming is reducing cloud cover further, it could create a feedback loop that accelerates heating.

“If cloud feedback is driving this, it could mean the climate is more sensitive than models suggest,” said Brian Soden of the University of Miami.

Why it matters

The distinction is critical. If warming is accelerating due mainly to cleaner air, the pace may stabilise over time. But if feedback loops are taking hold, the planet could heat faster than expected.

Current projections suggest about 2.7°C of warming this century under existing policies, but with uncertainty of around ±1°C. In a worst-case scenario, that could approach 3.7°C, making some regions effectively uninhabitable.

“2.7°C would still be severe, but more regions could adapt compared to 3.7°C,” Hausfather said.

The bottom line

While scientists debate the exact pace, there is broad agreement on one point: emissions must fall quickly.

“Global warming is accelerating slightly, but we’ve also lost time because we haven’t taken sufficient action,” Burgess said.

In other words, whether the recent surge is temporary or a sign of deeper change, the window to act is narrowing.