Global weather and science agencies have confirmed that the global average temperature for 2025 was 1.43°C above pre-industrial levels, making it either the second- or third-hottest in the 176-year observational record, the World Meteorological Organisation (WMO) said today.
The WMO collated nine datasets to reach the global average temperature for 2025, which has a margin of uncertainty of 0.13°C either higher or lower — meaning that 2025 could have exceeded 1.5°C above the pre-industrial average. The Paris climate agreement seeks to limit the global rise in temperature to "well below" 2°C above pre-industrial levels, and pursues a 1.5°C threshold.
The past 11 years, 2015-25 inclusive, were the 11 warmest on record and the past three years, 2023-25, were the three hottest across all nine datasets, the WMO said. Science and weather agencies agree that 2024 is the hottest year on record.
The atmospheric concentration of CO2 reached its highest level in the last 2mn years in 2024, the most recent full year with consolidated global observations, the WMO said. Key greenhouse gases (GHG) methane and nitrous oxide in 2024 reached their highest levels in at least the last 800,000 years, it added. Data show that levels of those three GHGs continued to increase in 2025.
CO2 stood at 423.9 parts per million (ppm) in 2024 — 3.5ppm higher than 2023 and 152pc of the estimated pre-industrial concentration, the WMO said. The concentration of 423.9ppm represents about 3.3 trillion t/CO2 in the atmosphere. The rise in CO2 concentration on the year in 2024 was the biggest annual increase since modern measurements began in 1957, "driven by continued fossil CO2 emissions, and reduced effectiveness of land and ocean carbon sinks", the WMO said.
The concentration of methane in the atmosphere rose to 1,942 parts per billion (ppb) in 2024 and that of nitrous oxide to 338ppb — 266pc and 125pc of pre-industrial levels, respectively.
But the "human-caused increase in the concentration of CO2 in the atmosphere is the largest driver of climate change", the WMO said.
"In this age of war, climate stress is also exposing another truth: our addiction to fossil fuels is destabilising both the climate and global security. Now more than ever, we must accelerate a just transition to renewable energy", UN secretary general Antonio Guterres said, when the WMO data were released.
"Human activities are increasingly disrupting the natural equilibrium and we will live with these consequences for hundreds and thousands of years", WMO secretary general Celeste Saulo said.
The WMO collates data from the EU's Copernicus, Japan's Meteorological Agency, the UK's Met Office, the US' National Aeronautics and Space Administration and National Oceanic and Atmospheric Administration, and US non-profit Berkeley Earth. It also uses a UK-US dataset, DCENT and two Chinese datasets.
