WMO’s annual assessment: a global climate alert
The new annual report by the World Meteorological Organization (WMO) on the “State of the Global Climate 2025”, published on World Meteorological Day, issues a very serious warning to the planet: Earth is undergoing a phase of accelerated warming that threatens ecosystems, food security, and global economic stability.
The state of the global climate: record heat and millennia of warming
According to the report, the years between 2015 and 2025 were the 11 warmest years since measurements began in 1980. Rising concentrations of greenhouse gases in the atmosphere, such as carbon dioxide, methane, and nitrous oxide in 2024 (the latest year for which consolidated global data is available) reached the highest levels in the last 800,000 years. This volume of concentrations reduces the rate at which energy leaves the Earth’s system. Earth’s energy imbalance, a new indicator in this year’s report, leads to an accumulation of excess energy, making oceans much warmer, weather phenomena increasingly extreme, and threatening health and food supplies.
The WMO report explains that due to the persistence of CO2 in the atmosphere and the thermal inertia of the oceans, many of the climate changes already triggered, such as sea level rise and glacier melt, are considered irreversible on a human timescale.
Average global surface temperature
Regarding the average surface temperature, according to the report, the last three years were the three warmest in 176 years of combined land and ocean records. 2025 is either the second or the third warmest year, depending on the dataset considered. Last year was indeed slightly cooler than the record reached in 2024, partly due to the transition from El Niño to La Niña. The report confirms that 2024 was the warmest year on record: the global average temperature was approximately 1.55 degrees Celsius higher than the pre-industrial average (1850-1900). 2025, despite benefiting at times from the cooling effect of La Niña, recorded an average global surface temperature of 1.43 °C above the 1850-1900 average.
Global climate and ocean heat storage
Returning to Earth’s energy imbalance, the report states that the vast majority of excess energy, almost 91%, was absorbed by the ocean in the form of heat. This heat stored in the ocean reached a new record in 2025. In 2025, ocean heat content reached its highest level in 66 years of observational records, surpassing the previous record set in 2024. In the last nine years, every single year has marked a new high for ocean heat content. Furthermore, the rate of ocean warming in the last twenty years (2005–2025) has more than doubled compared to that observed in the period 1960–2005.
In addition to absorbing most of the energy trapped by rising greenhouse gas concentrations, the ocean has also absorbed nearly 29% of anthropogenic carbon dioxide emissions over the last decade. While this helps buffer the effects of climate change, it also alters the chemical composition of the water, reducing its pH and thus contributing to the process of ocean acidification.
Glacier situation
Another 3% of the excess energy contributes to glacier melt. In the hydrological year 2024/2025 (i.e., from September 2024 to August 2025), again according to the report, glacier mass loss, calculated on a set of reference glaciers, is among the five most negative mass balances ever recorded. Eight of the ten most negative annual mass balances from 1950 to 2025 have occurred since 2016. In 2025, data showed exceptional levels of glacial mass loss in Iceland and along the Pacific coast of North America.
Sea ice extent
The report highlights that Arctic sea ice extent has decreased in all seasons since satellite measurements began in 1979. The annual maximum extent in 2025 was the lowest or second lowest ever recorded. Sea ice extent around Antarctica had shown slight long-term improvement until 2015, but since then, levels throughout the annual cycle have decreased considerably. In the last four years, the four lowest levels of Antarctic sea ice extent have been recorded.
Atmospheric carbon dioxide concentration
In 2024, the atmospheric carbon dioxide concentration reached the highest level in the last 2 million years. Concentrations of methane and nitrous oxide reached the highest levels in the last 800,000 years. The annual increase in carbon dioxide concentration in 2024 was the largest since modern measurements began in 1957. Real-time data show that levels of these three main greenhouse gases continued to rise in 2025.
Access the report by WMO on the “State of the Global Climate 2025”