Politicians must respond to the latest warnings that climate science has underestimated risks

Last week’s shockingly high temperatures in the northwestern US and Canada were – and are – very frightening. Heat and the fires it caused killed hundreds of people, and are estimated to have killed a billion sea creatures. Daily temperature records were smashed by more than 5C (9F) in some places. In Lytton, British Columbia, the heat reached 49.6C (121F). The wildfires that consumed the town produced their own thunderstorms, alongside thousands of lightning strikes.

An initial study shows human activity made this heat dome – in which a ridge of high pressure acts as a lid preventing warm air from escaping – at least 150 times more likely. The World Weather Attribution Group of scientists, who use computer climate models to assess global heating trends and extreme weather, have warned that last week exceeded even their worst-case scenarios. While it has long been recognised that the climate system has thresholds or tipping points beyond which humans stand to lose control of what happens, scientists did not hide their alarm that an usually cool part of the Pacific northwest had been turned into a furnace. One climatologist said the prospect opened up by the heat dome “blows my mind”.