Carbon Budget for 1.5°C May Be Exhausted in Three Years, Warn Scientists

Just over three years left before the carbon budget for limiting global warming to 1.5°C is used up

June 19, 2025

According to the Indicators of Global Climate Change (IGCC) report published today in Earth System Science Data, with current CO₂ emissions levels, the remaining budget (130 billion tonnes) is being rapidly depleted.

Dr. Chris Smith, senior scientist at Vrije Universiteit Brussel and second author on the study, highlighted the critical trends:

“2024 continued the pattern of rising greenhouse gas concentrations—the main driver of global heating. Although air pollution from fossil fuels is decreasing, widespread wildfires are partly offsetting the cooling effect from reduced aerosols.”

The study, produced by a team of 61 scientists from 54 institutions, including IPCC contributors, provides the most up-to-date and comprehensive assessment of the state of the climate system. This year’s report expands to include 10 key indicators, such as sea-level rise and global land precipitation.

Key Findings:

Global surface temperatures in 2024 were 1.52°C above pre-industrial levels, with 1.36°C directly linked to human activity.
Human-induced warming is increasing at 0.27°C per decade, with the last decade (2015–2024) 0.31°C warmer than the one before.
The carbon budget for 1.6°C or 1.7°C could be exhausted within nine years.
The ocean, absorbing over 90% of excess heat, reached record temperatures in 2024, driving sea level rise, weather extremes, and marine ecosystem disruption.
Global mean sea level has risen 26 mm between 2019 and 2024, more than double the long-term rate.

Without deep and rapid emissions cuts, the impacts will only intensify. Lead author Prof. Piers Forster (University of Leeds) emphasized that the pace of climate action still lags dangerously behind the science:

“Temperatures have increased every year since the last IPCC report in 2021.”

The report underscores that the impacts of climate change—from heatwaves and rising seas to ecosystem collapse—are entirely driven by human activities, notably the burning of fossil fuels and deforestation.

Dr. Smith added: “While declining air pollutants may improve health outcomes, their reduced presence means less cooling, underscoring the need to also reduce methane and other short-lived climate pollutants to limit warming in the short term.”

The findings reinforce the rapidly narrowing window to meet the Paris Agreement goals. Net-zero CO₂ emissions—and reductions in all greenhouse gases—are essential to stabilise global temperatures and avert escalating impacts.

“At a time when the EU are considering weakening their 2040 greenhouse gas emissions reduction target, our report shows that the pace of climate change continues unrelented. Now is not the time for backsliding; Europe needs to take the lead in decarbonization”. Dr. Smith concludes.

Reference:

Forster, P. M., Smith, C., Walsh, T., et al. 2025: Indicators of Global Climate Change 2024: annual update of key indicators of the state of the climate system and human influence, Earth Syst. Sci. Data, 17, 2641–2680, https://doi.org/10.5194/essd-17-2641-2025

Contact:

Chris Smith: chris.smith@vub.be | cjsmith.be | +32 492 88 62 89