Study: Global Fossil-Fuel CO2 Emissions to Hit Record 38.1 Billion Tonnes in 2025 — 1.5°C Budget Exhausted in Four Years

Global fossil-fuel CO2 emissions set to reach a new high in 2025

New research published as world leaders gather for COP30 in the Brazilian Amazon warns that CO2 emissions from fossil fuels are projected to reach a record 38.1 billion tonnes in 2025. The annual Global Carbon Budget — which assesses CO2 from burning oil, gas and coal, cement production and land-use change such as deforestation — links these emissions to the temperature limits set in the 2015 Paris Agreement.

An international team of scientists, writing in the journal Earth System Science Data, estimates fossil-fuel emissions will be about 1.1% higher in 2025 than in 2024. The study concludes that the rapid deployment of renewables worldwide has not yet offset growing global energy demand.

Carbon budget and urgency

The researchers calculate a remaining carbon allowance of 170 billion tonnes of CO2 to keep warming within 1.5°C above pre-industrial levels. At current emission rates, that budget would be exhausted in roughly four years — a gap the lead author describes as making the 1.5°C target essentially "impossible" without immediate, deep cuts.

"This equates to four years of emissions at the current rate before the budget for 1.5°C is exhausted, so that is impossible, essentially." — Pierre Friedlingstein, University of Exeter

Regional trends and drivers

The report highlights mixed regional trends: China’s fossil emissions were largely flat this year — particularly coal — which could signal a shift as renewables expand, though policy uncertainty means a definitive peak is not yet clear. In the United States, coal-related CO2 rose by 7.5% as higher natural gas prices prompted a switch back to coal for power generation. Both the US and the EU reversed recent declines and recorded increased emissions this year, partly driven by cooler winter months and higher heating demand.

India recorded a smaller rise in CO2 than in recent years, aided by an early monsoon and strong growth in renewable generation.

All emissions and land use

When emissions from land-use change are included, humanity’s total projected CO2 output for the year reaches about 42.2 billion tonnes, slightly below last year’s level but subject to considerable uncertainty. Researchers point to reduced deforestation and fewer large fires in South America — partly linked to the end of very dry 2023–2024 El Niño conditions — as a factor in lower net land-use emissions.

The authors also note that 35 countries have now reduced their emissions while still growing their economies — roughly double the number from a decade ago — showing that emissions reductions alongside economic growth are achievable with the right policies.

Implications for COP30

Released as COP30 convenes in Belém, the study casts a long shadow over the talks, which this year proceed without the participation of the United States, the world’s second-largest emitter. Observers warn that national climate plans remain insufficient and call for far stronger, immediate action to avert the most dangerous impacts of warming.

Source: Global Carbon Budget report, published in Earth System Science Data.