Why are we seeing record heat across the northern hemisphere? Because the planet is getting hotter. And we ain’t seen nothing yet – it’s going to get a lot hotter still.
Scotland hit 33.2°C on 28 June, for instance, passing the previous record of 32.9°C set in August 2003 – though the Met Office says this reading may actually be due toÌý. And in Oman on 26 June, , even at night. That’s the highest minimum temperature ever recorded.
More heat records tumbling is exactly what we expect to see on a warming planet. By contrast, in an unchanging climate, there should be fewer and fewer records broken over time.
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However, talk of a heatwave across the entire northern hemisphere is misleading, as parts of the hemisphere are cooler than the recent average for this time of year.
Hotter and hotter
You can see this for yourself by looking at temperature anomalies on . There you will also see that some of the biggest recent heat anomalies have been in parts of Antarctica, where it’s the middle of winter and well below freezing – but much less below freezing than normal.
The thing is, average temperatures are much higher than they used to be. Global average surface temperatures have risen by more than 1°C since preindustrial times and have shot up particularly fast in the last five years or so.
That means when it does get hot, there’s a good chance it will be hotter than ever before. What’s more, , as the air over land is drier and heats up faster, and the northern hemisphere is warming faster than the southern hemisphere, as there’s more land.
So while there will be local weather-related explanations for each individual heatwave, the main reason for the record-breaking heat in several parts of the world is global warming.
Think of these extreme heat events as the height of waves in a bathtub. As you fill up the bathtub, the waves will get ever higher relative to the bottom of the bath, even if the individual waves themselves are no bigger.
That said, the waves might be getting bigger too. There is growing evidence that the rapid warming of the Arctic is affecting the jetstream that drives weather patterns across the northern hemisphere, making it more likely for particular conditions to persist for longer. And the longer heat persists, the hotter it can get, as the land and buildings dry out and warm up.
So is this the new normal? Well, it’s the normal for a little while. Global temperatures have actually fallen slightly since the strong El Niño of 2016 (a global climate event that sees the oceans release heat into the atmosphere). It is possible they will fall little further in the next year or two, especially if there’s a La Niña (the opposite event during which the oceans absorb more heat).
But in the longer term, as the world continues to warm, there will be ever more severe heatwaves and yet more heat records will tumble.
While some might welcome the sunshine, this is serious. Heatwaves can be deadly for the elderly and vulnerable – more than a dozen deaths are already being blamed on the heat in Canada.
There’s also a limit to how much work we can do in the heat. Rising temperatures are already affecting the global economy by reducing the productivity of workers, especially in developing countries. And if we don’t manage to limit global warming, it could get so hot and humid in future heatwaves that people without air conditioning will die.
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