Global warming is advancing at a quarter of a degree per decade, the highest rate per since records began.

According to a new report by over 50 leading international scientists, including Imperial College London researchers Joeri Rogelj and Robin Lamboll, the remaining carbon budget - how much CO₂ can be emitted while limiting warming to 1.5°C - has significantly reduced compared to the IPCC’s 2021 estimate (from 500 Gt to just 200 Gt).

Professor Joeri Rogelj, from the Centre for Environmental Policy and Director of Research at the Grantham Institute at Imperial, said:

“The 1.5°C carbon budget is smaller than ever. Global warming stands now at 1.3°C, dangerously close to the Paris Agreement's 1.5°C limit. Significantly lowering greenhouse gas pollution over the next 5 to 10 years is the only way to ensure that the planet is not warming by another quarter of degree by 2035.”

Staying within this budget would give the world a 50-50 chance at limiting warming to 1.5°C and amounts to around five years of present-day emissions. The report shows that human-induced warming rose to 1.19°C over the past decade (2014-2023).

The reduction of the carbon budget from the IPCC’s 2021 assessment also reflects a potential ‘information gap’, caused by the rapid changes in climate indicators (with the next IPCC assessment planned for 2027).

The high rate of warming recorded in the study is attributed to a combination of consistently high greenhouse gas emissions, equivalent to 53 billion tonnes of CO₂ per year, as well as ongoing improvements in air quality, which are reducing the strength of human-caused cooling from particles in the atmosphere.

Looking at 2023 in isolation, warming caused by human activity reached 1.3°C. This is lower than the total culminative amount of warming (1.43 °C), indicating that natural climate variability, in particular El Niño, also played a role in 2023’s record temperatures. 

One key development that the report explores are the effects of sulphur emissions reductions from the global shipping industry.

Sulphur causes cooling by directly reflecting sunlight back to space and by helping more reflective clouds to form. Therefore, lower sulphur emissions, which brings numerous benefits such as reducing air pollution and improving human, tree and plant health, exposes the world to more warming. The report states that we should expect further reductions in the cooling effect of sulphur as emissions decline.

Dr Robin Lamboll, research fellow at the Centre for Environmental Policy at Imperial, said:

“This report shows the climatic consequences of another disappointing year […] While there are signs that global emissions are no longer growing, we need them to fall rapidly in order to preserve even the Paris agreement fallback targets.”

This research comes as climate experts meet in Bonn to prepare the ground for the COP29 climate conference which takes place in November in Baku, Azerbaijan.

It is hoped that the report will play a strong role in informing new Nationally Determined Contributions, the improved climate plans that every country in the world has promised to put forward to the United Nations Framework Convention on Climate Change (UNFCCC) by 2025 to cut emissions and adapt to climate impacts.

The new report is accompanied by an open data, open science platform – the Climate Change Tracker’s Indicators of Global Climate Change dashboard which provides easy access to updated information on the key climate indicators.