Rising humidity levels are making heatwaves unbearable

31 July 2023

Heatwaves, which have been experienced in a number of regions in the northern hemisphere in recent weeks, are being aggravated by increased levels of humidity, which is being precipitated by climate change. While it might be thought higher temperatures would cause moisture to evaporate, warmer air is capable of holding more water vapour than cooler air.

Sea surface temperatures have been steadily climbing globally, as the oceans absorb something like 90 percent of the excess heat that humans are adding to the atmosphere. But since March, global sea surface temperatures have been skyrocketing above the norm. The North Atlantic, in particular, remains super hot, loading Europe’s air with extra humidity.

Parts of the east coast of Australia saw higher levels of humidity last week, which had the effect of “taking the bite” out of otherwise relatively cooler temperatures. That’s about the only instance when high humidity has an upside. Those sorts of humidity levels will be far from welcome come summer.