August Was the Joint Hottest Month Ever Measured, and the First Above 1.5 Degrees Since Last November

The oceans are the reason. The average sea surface temperature across the extra-polar ocean, between sixty degrees south and sixty north, was 21.07 degrees, the joint highest monthly figure for any month, matching March 2024, and a daily record of 21.11 was set within it. Tropical Pacific temperatures were exceptionally high as a strong El Niño builds, and El Niño events release heat from the ocean into the atmosphere; the global temperature record in 2023 and 2024 followed the last one. Samantha Burgess, strategic lead for climate at the European Centre for Medium-Range Weather Forecasts, which runs the service, called August a remarkable month in the global climate record and said the observations show how climate change is driving extremes across both the atmosphere and the oceans.

Europe

Western Europe's summer, June through August, was the warmest on record, surpassing 2003, the year the continent learned what a heatwave could do to its elderly. The European land temperature for August was 20.26 degrees, 1.10 above the recent average and the fourth warmest August for the continent as a whole. The drought was as consequential as the heat: France, Britain, Hungary, Romania and Serbia were all severely dry, and the Rhine, the Danube, the Southern Bug and the Dnieper ran at exceptionally low flows, which for the Rhine in particular means barges carrying half loads and industrial freight moving to rail and road at higher cost. Arctic sea ice, for what it is worth, was the twelfth lowest for August, an unremarkable figure in a remarkable month.

What the figure does and does not mean

A single month above 1.5 degrees does not mean the Paris threshold has been crossed; that is defined as a multi-decade average, and on that measure the world is still below the line, with the trend rising towards it. What a month like this does is bring forward the date. Every El Niño lifts the global figure for a year or two, and every one now starts from a higher floor; the peaks of 2023 and 2024 were the highest ever and the peak this El Niño produces, probably in 2027, is likely to be higher again. The bulletin does not forecast, but the arithmetic does.

For the Gulf, which spent the summer above forty-five degrees as it always does, the direct effect of a record August in the global average is small and the indirect effects are not. The heat that Europe experienced is the heat that fills this region's hotels and airports in July and August as residents leave; the low Rhine and Danube are the arteries of the export economies this region trades with; and the El Niño that is building now will shape the monsoon that South Asia's food prices depend on next year. Our guide to living and working through the local version of this is in the piece on what actually helps in extreme heat, and the case that the heat has become a health hazard the region plans for badly is in our report on France's heatwave deaths.