1275. Copernicus: May 2025 Was the Second Warmest May on Record

According to the Copernicus Climate Change Service (C3S), May 2025 was the second warmest May on record, with an average surface temperature of 15.79°C, 0.53°C higher than the average May temperature from 1991 to 2020. At the same time, the temperature in May 2025 was 1.40°C higher than the estimated average from 1850 to 1900, marking the end of 21 of the past 22 months in which the global average temperature was more than 1.5°C higher than pre-industrial levels.

Additionally, the 12-month period from June 2024 to May 2025 was 0.69°C higher than the 1991-2020 average and 1.57°C higher than pre-industrial levels. According to researchers, the end of an unprecedentedly long period of months with temperatures above 1.5°C compared to pre-industrial levels may be a moment of respite for the planet, but the 1.5°C threshold is expected to be crossed again in the near future as the climate system continues to warm.

The global average temperature in boreal spring (March-May) of 2025 was 0.59°C higher than the 1991-2020 average, making it the second warmest on record after the boreal spring of 2024. The largest positive anomalies were recorded in western Central Asia, northeastern Russia, Greenland, and western Antarctica, while negative anomalies were observed in Hudson Bay, southern and northeastern Africa, India, northern Australia, and eastern Antarctica.

SSTs remained abnormally high in many ocean and sea areas. In particular, large areas of the northeastern North Atlantic, hit by a marine heatwave, recorded their highest SSTs on record for the month. Large parts of the Mediterranean Sea were significantly warmer than normal. The average sea surface temperature (SST) from 60°S to 60°N in May 2025 was 20.79°C, the second highest value on record for the month and 0.14°C lower than the value recorded in May 2024.

Contributor: IIYAMA Miyuki, Information Program