November 2025
Save the Climate has released a report by Jean Poitou titled “Global Climate - Where Are We Today,” providing an assessment of the climate situation as of the third quarter of 2025. We summarize its key points in this communique.
Over a little more than a century, the Earth’s global mean surface temperature has increased by 1.24 °C. The increase has been smaller over the oceans than over the continents, where it has accelerated and reached 1.9 °C in 2024.
Warming is caused by the accumulation of greenhouse gases in the atmosphere. Human activities emit mainly carbon dioxide, methane, and nitrous oxide. After decades of steady growth, the annual emissions rate has begun to decline. However, the atmospheric concentration of these gases continues to rise, increasing the warming.
Most of the warming is due to CO₂. Among human activities, there are two that cause cooling:
- Changes in land use, particularly deforestation, lead to a significant increase in the reflectivity of affected soils. Because they reflect more of the incoming solar radiation, their warming is reduced;
- Aerosols produced by human activities create a layer that reduces the intensity of solar radiation reaching the Earth’s surface. However, aerosol emissions must be reduced to fight pollution.
The excess heat is distributed very unevenly within the Earth system components. The ocean absorbs about 91% of it, while the atmosphere takes in only about 1%.
Human activities are responsible for nearly all of the observed warming; the Sun’s contribution is marginal.
Precipitations show very high variability, with no clear trend in the evolution of total global rainfall.
Warming raises the sea-level—partly through the thermal expansion of seawater and partly through water additions from melting polar and alpine glaciers. As warming increases, the rate of sea-level rise increases.
The Paris Agreement specified that global warming should ultimately not exceed 2 °C and, if possible, be limited to 1.5 °C. Equilibrium warming depends mainly on the total amount of carbon dioxide emitted since the start of the industrial era. At the current emission rate, and to keep the probability of exceeding these temperature thresholds below 50%, the emissions limit will be reached in less than 4 years for 1.5 °C of warming, and in 26 years for 2 °C.
One consequence of global warming is an increase in the number or intensity of extreme events—events whose magnitude, duration, or spatial extent is uncommonly large.
Jean Poitou’s study on this issue is available (pdf format): “Global Climate - Where Are We Today” or html version
Copyright © 2025 Association Sauvons Le Climat
