Are heatwaves evidence that climate change is speeding up?

Estimates of Earth’s average temperature, having set a new record on July 3rd, have yet to fall back below the previous record, which was set just last year. That a run of very hot days should happen in July is, by itself, perhaps unsurprising. Two-thirds of the Earth’s land is in the northern hemisphere, and land warms up faster than water does, so northern summers are the hottest times of year for the planet as a whole. But the highest temperatures tend to come later in the season. That this year’s should start so early, rise so high and run so long is unprecedented.