Global Temperatures Continue to Rise, Pushing Climate Boundaries

In Madrid, Spain, on June 1, 2025, women sought relief from the heat at a fountain in Retiro Park.

May of the same year was the second-warmest May on record, surpassed only by May 2024. This contributed to the second-hottest March-May spring in the northern hemisphere.

Global surface temperatures in May were, on average, 1.4 degrees Celsius higher than the pre-industrial period (1850-1900), when widespread fossil fuel burning began. This ended a period of extreme heat where 21 of the previous 22 months exceeded 1.5C above pre-industrial levels. Scientists anticipate this break to be temporary.

Carlo Buontempo, director of C3S, stated that the 1.5C threshold is expected to be surpassed again soon due to ongoing climate warming. The primary driver of climate change is greenhouse gas emissions from burning fossil fuels. The previous year was the planet's hottest on record.

A study by the World Weather Attribution group revealed that human-caused climate change made a record-breaking heatwave in Iceland and Greenland last month approximately 3C hotter than it would have been otherwise. This contributed to significant melting of Greenland's ice sheet. Sarah Kew, a researcher at the Royal Netherlands Meteorological Institute, noted that even cold-climate countries are experiencing unprecedented temperatures.

The 1.5C global warming threshold is the limit that countries aimed to prevent under the Paris climate agreement to mitigate the worst effects of warming. While the world has not yet technically breached this target, which refers to an average global temperature of 1.5C over decades, some scientists believe it is no longer realistically achievable. They are urging governments to accelerate CO2 emission reductions to limit the extent of warming and the intensification of extreme weather events. C3S's records, which are cross-checked with global temperature records dating back to 1850, begin in 1940.