Carbon budget · updated 31 October 2026
Carbon budget: how much CO₂ can we still emit for 1.5 °C?
For a 50% chance of keeping long-term warming to 1.5 °C. At about 42 billion tonnes per year (1,331 tonnes every second), that is 1.3 years — used up around February 2028.
Remaining 1.5 °C carbon budget at constant emissions (billion tonnes CO₂)
What it means, according to scientists
The Indicators of Global Climate Change project, led by Piers Forster with dozens of climate scientists, updates the IPCC's numbers every year. Their 2025 update put the remaining budget at about 130 billion tonnes of CO₂ from the start of 2025 — roughly three years of current emissions.
The IPCC's starting point for the same budget, in 2020, was 500 billion tonnes. Most of that difference is the CO₂ emitted since, plus updated estimates of how much warming has already happened.
Running out of the 1.5 °C budget does not make 1.5 °C instantly “lost” — warming responds over years — but it means staying under it would require temporarily overshooting and then removing CO₂ from the air. Every tonne avoided still lowers peak warming.
Sources: Forster et al. (2025), Indicators of Global Climate Change 2024;Global Carbon Budget;IPCC AR6 WG1 SPM (D.1).
Frequently asked questions
What is the carbon budget?
The remaining carbon budget is how much more CO₂ the world can emit while still having a given chance of limiting warming to a temperature goal, such as 1.5 °C. It exists because warming is roughly proportional to the total CO₂ ever emitted.
How much of the 1.5 °C carbon budget is left?
Scientists estimated about 130 billion tonnes of CO₂ remained from the start of 2025 for a 50% chance of 1.5 °C. At current emissions of about 42 billion tonnes per year, roughly 53 billion tonnes are left today.
What happens when the carbon budget runs out?
The world would be on course to exceed 1.5 °C as a long-term average. Warming would continue until net CO₂ emissions reach zero; temperatures could only come back down with large-scale net removal of CO₂ from the atmosphere.
How certain is this estimate?
Quite uncertain. Estimates of the budget depend on the climate's sensitivity, future non-CO₂ emissions such as methane, and how warming is measured. Small changes can shift the 1.5 °C budget by tens of billions of tonnes — which, at current emissions, is about a year. The budget for 2 °C is many times larger.
Source:Indicators of Global Climate Change 2024 (Forster et al. 2025); Global Carbon Budget
Licence: Derived estimate based on CC BY 4.0 publications. Linear extrapolation at constant emissions.
Latest data: 31 October 2026 · Checked: 31 October 2026 ·Download CSV · Methodology