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Researchers from 911½ñÈÕºÚÁÏ have contributed to a major international climate assessment showing that the Earth is accumulating heat at an accelerating rate, with human-induced warming reaching 1.37°C above pre-industrial levels in 2025.

The latest annual update from the Indicators of Global Climate Change (IGCC) initiative was co-authored by Professor Joeri Rogelj and Dr Robin Lamboll from 911½ñÈÕºÚÁÏ's Centre for Environmental Policy and the Grantham Institute. The report finds that if current emissions trends continue, the world is likely to exceed 1.5°C of warming within around four years.

Published in , the study brings together more than 70 scientists from 17 countries to provide an annual assessment of the state of the climate system and humanity's influence on it.

The researchers found that the Earth's energy imbalance, a measure of how much excess heat is being trapped by greenhouse gases, has more than doubled since the late twentieth century and is now at a record high.

"As extreme weather causes communities around the world to struggle and suffer, this report provides an annual ticking clock of the causes behind it. The absence of clear breaks in current trends, from global warming through to the greenhouse gas emissions driving it, is deeply worrying. We are close to warming the planet beyond 1.5°C, a critical benchmark beyond which climate impacts are expected to become disproportionately stronger and harder to manage." - Professor Joeri Rogelj

Tracking a rapidly changing climate

The Earth constantly receives energy from the Sun and releases energy back into space. When more energy enters the climate system than leaves it, the planet warms.

According to the report, the Earth's energy imbalance has increased significantly in recent decades, providing one of the clearest indicators that climate change is accelerating. The excess heat is being absorbed across the climate system, warming the atmosphere and oceans, melting ice, and contributing to rising sea levels.

The study found that average global temperatures during 2016 - 2025 were 1.26°C above pre-industrial levels, with 1.24°C of that warming attributable to human activities. Human-induced warming reached 1.37°C in 2025 alone.

Researchers estimate that the rate of human-induced warming over the last decade was approximately 0.27°C per decade, matching the highest rate observed in the instrumental record.

Greenhouse gas emissions remain at record highs

The findings show that global greenhouse gas emissions continue to rise. Total emissions reached a record 56.8 billion tonnes of carbon dioxide equivalent in 2024, driven primarily by the continued use of fossil fuels.

The researchers also found that reductions in air pollution are revealing more of the warming effect caused by greenhouse gases. Sulphur dioxide emissions, which have historically had a cooling effect by reflecting sunlight, have declined as countries implement measures to improve air quality.

While this brings important public health benefits, it also means that some previously masked warming is becoming more apparent.

Despite emissions remaining at historically high levels, the report notes there is some evidence that the growth in carbon dioxide emissions is slowing.

 Marine heatwaves and rising seas

The 2025 assessment introduces a new indicator tracking marine heatwaves - periods of unusually warm ocean temperatures that can damage ecosystems and disrupt fisheries.

The researchers found that the number of marine heatwave days has more than tripled globally since 1991. In 2025 alone, oceans around the world experienced 65 marine heatwave days.

Marine heatwaves can have wide-ranging consequences, including impacts on biodiversity, food production and coastal economies. They can also affect how the ocean absorbs carbon dioxide and influence weather patterns on land.

The study also reports that global mean sea level has risen by 23 centimetres since 1901. The rate of sea level rise is accelerating as warming oceans expand and glaciers and ice sheets continue to lose mass.

“This report shows that the impacts of climate change are increasingly visible, not just in the ever-breaking temperature trends on land, but in the accelerating rise and warming of the seas. The most hopeful thing we can say about recent trends is that total CO2 emissions remained fairly level this year.” - Dr Robin Lamboll

A shrinking carbon budget

The report updates estimates of the remaining carbon budget - the amount of carbon dioxide that can still be emitted while maintaining a reasonable chance of limiting warming to 1.5°C.

Researchers estimate that around 130 billion tonnes of carbon dioxide remained in the budget at the start of 2026. At current rates of emissions, that budget could be exhausted within approximately three years.

The authors say the findings highlight the scale and speed of ongoing climate change, as well as the importance of accelerating efforts to reduce greenhouse gas emissions during this critical decade.

The study also warns that many of the global observing systems used to monitor climate change are facing increasing funding pressures. The assessment relies on more than 40 international datasets that track changes across the atmosphere, oceans, land and ice.

Maintaining these long-term observations, the researchers say, will be essential for understanding how the climate is changing and informing evidence-based decision-making in the years ahead.

The paper, , is published in Earth System Science Data.