Global carbon emissions on track to exhaust 1.5°C budget in three years, study warns

The central estimate of the remaining carbon budget for 1.5°C is 130 billion tons of carbon dioxide (CO₂) (from the beginning of 2025). This would be exhausted in a little more than three years at current levels of CO₂ emissions, according to the latest Indicators of Global Climate Change study published in the journal Earth System Science Data, and the budget for 1.6°C or 1.7°C could be exceeded within nine years.

Prof. Piers Forster, Director of the Priestley Center for Climate Futures at the University of Leeds and lead author of the study, said, “Our third annual edition of Indicators of Global Climate Change shows that both warming levels and rates of warming are unprecedented.

“Continued record-high emissions of greenhouse gases mean more of us are experiencing unsafe levels of climate impacts. Temperatures have risen year-on-year since the last IPCC report in 2021, highlighting how climate policies and pace of climate action are not keeping up with what’s needed to address the ever-growing impacts.”

This year’s update of key climate system indicators carried out by a team of over 60 international scientists included two additional indicators, sea-level rise and global land precipitation, to give a total of 10 indicators1. This information is crucial for decision-makers seeking a current, comprehensive picture of the state of the global climate system.

In 2024, the best estimate of observed global surface temperature rise was 1.52°C, of which 1.36°C can be attributed to human activity2. The high level of human-induced warming and its high warming rate are due to global greenhouse gas emissions remaining at an all-time high in recent years.

According to the study, 2024’s high temperatures are “alarmingly unexceptional,” given the level of human-caused climate change. This human influence is at an all-time high and, combined with natural variability in the climate system (which causes temperatures to vary naturally year-to-year), has pushed global average temperature rise to record levels.

While reaching 1.5°C of global temperature rise in a single year does not mean there has been any breach of the landmark Paris Agreement—for that, average global temperatures would need to exceed 1.5°C over multiple decades—these results do reaffirm how far and fast emissions are heading in the wrong direction. And the impacts will only stop worsening when CO₂ emissions from fossil fuels and deforestation reach net zero.

When analyzing longer-term temperature change, best estimates show that between 2015–2024, average global temperatures were 1.24°C higher than in pre-industrial times, with 1.22°C caused by human activities, meaning that, essentially, our best estimate is that all of the warming we have seen over the last decade has been human-induced.

Human activities have resulted in the equivalent of around 53 billion tons of CO₂ (Gt CO₂e) being released into the atmosphere each year over the last decade, primarily due to increasing emissions from burning fossil fuels and deforestation. In 2024, emissions from international aviation—the sector with the steepest drop in emissions during the pandemic—also returned to pre-pandemic levels.

GHG emissions have also led to higher levels of greenhouse gases accumulating in the atmosphere. Combined with declines in emissions of sulfur dioxide (SO₂) leading to planet-cooling aerosols, the outcome is that the planet is continuing to heat up.

The damage caused by aerosols to human health far outweighs any minimal cooling “gains,” and there are other short-lived GHGs that can and should be tackled alongside CO₂, such as methane (CH₄), which could provide short-term cooling to compensate for the aerosol decline.

Human activities have also been affecting the Earth’s energy balance. Surplus heat accumulating in the Earth’s system at an accelerating rate is driving changes in every component of the climate system. The rate of global heating seen between 2012 and 2024 has about doubled from the levels seen in the 1970s and 1980s, leading to detrimental changes of vital components, including sea level rise, ocean warming, ice loss, and permafrost thawing.

Dr. Karina Von Schuckmann, Senior Advisor, Ocean Science for Policy at Mercator Ocean International said, “The ocean is storing about 91% of this excess heat driven by greenhouse gas emissions, which leads to ocean warming. Warmer waters lead to rising sea levels and intensified weather extremes, and can have devastating impacts on marine ecosystems and the communities that rely on them. In 2024, the ocean reached record values globally.”

Between 2019 and 2024, global mean sea level has also increased by around 26 mm, more than doubling the long-term rate of 1.8 mm per year seen since the turn of the twentieth century.

Dr. Aimée Slangen, Research Leader at the NIOZ Royal Netherlands Institute for Sea Research said, “Since 1900, the global mean sea level has risen by around 228 mm. This seemingly small number is having an outsized impact on low-lying coastal areas, making storm surges more damaging and causing more coastal erosion, posing a threat to humans and coastal ecosystems.

“The concerning part is that we know that sea-level rise in response to climate change is relatively slow, which means that we have already locked in further increases in the coming years and decades.”

The IPCC’s last assessment of the climate system, published in 2021, highlighted how climate change was leading to widespread adverse impacts on nature and people, with rapid and deep reductions in GHGs emissions needed to limit warming to 1.5°C.

Prof. Joeri Rogelj, Research Director at the Grantham Institute and Climate Science & Policy Professor at the Center for Environmental Policy at Imperial College London said, “The window to stay within 1.5°C is rapidly closing. Global warming is already affecting the lives of billions of people around the world.

“Every small increase in warming matters, leading to more frequent, more intense weather extremes. Emissions over the next decade will determine how soon and how fast 1.5°C of warming is reached. They need to be swiftly reduced to meet the climate goals of the Paris Agreement.”

Other key findings:

• Human-caused warming has increased at a rate of around 0.27°C/decade (2015–2024).

• The most recent decade (2015–2024) was 0.31°C warmer than the previous decade (2005–2014). These changes, although amplified somewhat by the exceptionally warm years in 2023 and 2024, are broadly consistent with warming rates over the last few decades.

• The rapid warming over the last few decades has resulted in record extreme temperatures over land, with average maximum temperatures reaching 1.9°C over the decade 2015–2024 and rising at a substantially faster rate than global mean surface temperature.