The period from 2015 to 2025 marks the eleven hottest years ever recorded globally, according to the World Meteorological Organization, which warns of an unprecedented imbalance in the Earth’s climate system in its annual report released on the occasion of World Meteorological Day.
This trend is driven by the continuous rise in greenhouse gas concentrations, leading to sustained warming of the atmosphere and oceans, as well as accelerated ice melt.
In 2025, the global average temperature stood about 1.43 degrees Celsius above pre-industrial levels, ranking the year among the two or three warmest ever recorded.
For the first time, the report highlights Earth’s energy imbalance as a key indicator. This measures the difference between the energy received from the Sun and that radiated back into space. It has been steadily increasing since the 1960s and reached a record high in 2025.
This imbalance reflects an accumulation of energy in the climate system, largely absorbed by the oceans, which take in more than 91 percent of this excess.
Over the past two decades, oceans have absorbed each year an amount of energy equivalent to nearly 18 times global energy consumption. While this plays a crucial role in regulating temperature, it also leads to faster ocean warming and increased acidification. In 2025, ocean heat content reached a new record, with the rate of warming more than doubling since 2005.
At the same time, ice melt continues at a rapid pace. The Greenland and Antarctic ice sheets are experiencing significant losses, while sea ice extent remains close to historic lows, particularly in the Arctic.
Exceptional melting events were recorded in 2025, notably in Iceland and along the Pacific coast of North America. These changes are contributing to rising sea levels, whose acceleration has been observed since satellite measurements began in the 1990s.
On land, this excess energy is translating into more frequent and intense extreme weather events. Heatwaves, droughts, wildfires, storms and floods caused thousands of deaths, affected millions of people and resulted in billions of dollars in economic losses in 2025.
The report also highlights the cascading impacts of climate change on food security, population displacement and public health. Changes in temperature and rainfall patterns are notably influencing the spread of diseases such as dengue and increasing risks linked to heat stress.
In response, the United Nations is calling for urgent action. UN Secretary-General António Guterres stressed that eleven consecutive years of record heat represent a clear signal that immediate measures are needed.
For her part, World Meteorological Organization Secretary-General Celeste Saulo warned that human activities are increasingly disrupting the natural balance, with consequences expected to last for centuries.
Based on contributions from numerous meteorological services and international experts, the report is intended as a decision-making tool to address the climate emergency.
