First year above 1.5 C of warming

In January 2025 the European Copernicus Climate Change Service, followed by the World Meteorological Organization and other groups, reported that 2024 was the warmest year in the instrumental record and the first calendar year with global average temperature more than 1.5 degrees C above the 1850 to 1900 level. Copernicus put it at about 1.60 degrees C, and the WMO's combined estimate was about 1.55 degrees C, with an uncertainty of 0.13. It beat the previous record, 2023, and the ten warmest years on record were all in the last decade.¹²

The main cause is the long-term rise in greenhouse gases, mostly from burning fossil fuels, which has produced about 1.36 degrees C of warming to date. The El Nino of 2023 and 2024, a natural warm phase in the Pacific, added a short-term boost of a few tenths of a degree. The Paris Agreement of 2015 aims to hold warming well below 2 degrees C and pursue 1.5 degrees C, and its meaning is a long-term average, usually over about 20 years, so one year above 1.5 does not mean the target has been missed, but it shows how close the world is. The Keeling Curve had recorded carbon dioxide rising from about 315 parts per million in 1958 to above 420 in 2024.²³⁴

The year saw record heat, floods, and storms, and widespread coral bleaching. Policy attention turned to whether the 1.5 degree limit can be held, and scientists now commonly expect it to be exceeded for a time, called overshoot, before any possible return.¹