Heatwaves and climate change: A cooler look

By Richard Black, ECIU Director

So it’s all done and dusted, then. Northern Europe has had a huge heatwave – science has shown that climate change made it more likely to occur – and so we should loudly proclaim ‘this is climate change, people’.


Er – no. Not in my view, anyway.

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Sweden has seen fires north of the Arctic Circle... extraordinary! Image: CTIF

Lest you think I’ve had an attack of the Ridleys, let me explain. I’ve written here before that one hot year doesn’t ‘prove’ climate change… because logically, if it does, then one cold one disproves it. And if a hot year doesn’t prove climate change, then one heatwave in one part of the globe certainly doesn’t.

You may quibble with ‘one part of the globe’ – and that’s fair. The northern European heatwave has coincided with a remarkable number of events in other parts of the world too. Japan, Algeria, Oman, California … all have seen extraordinary heat in recent weeks, the first two breaking national records and the third setting what is believed to be the hottest temperature at the daily minimum (night-time) recorded anywhere in the world.

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The world is showing a lot of red... but also a lot of blue. Image: ClimateReanalyzer

The point is… that still leaves a heck of a lot of the world where records aren’t being broken.

In Europe, for example, attention has naturally focussed on the tragic wildfire at Mati in Greece and the blazes north of the Arctic Circle in Sweden. But the area consumed by wildfires across the continent as a whole is actually below average this summer.

That’s because the two countries that usually have the most conflagrations, Spain and Portugal, saw early summer weather a little cooler and wetter than normal.

Delving into the global temperature data, you see also that 2018 is not going to set any records. The first half of the year has been cooler than 2017, 2016 and 2015 – very similar, in fact, to 2014. That other totemic marker of climate change, Arctic sea ice, also appears unlikely to set any records this year – the July report from the National Snow and Ice Data Center reports that ‘…the rate of summer ice loss has been unremarkable thus far.’

So here’s the issue. If you nail your colours to the mast of the heatwave, and proclaim that it ‘proves climate change is here’, or some variant of the phrase – then what are you going to say later in the year, when reports start to emerge showing that globally – or even regionally, bearing in mind the caution above about Spain and Portugal – 2018 wasn’t that remarkable?

The thing is – to prove that climate change is real, you don’t need to cite any given heatwave. You don’t have to base your argument on a drought or a hurricane or a flood. There is abundant evidence already in the long-term records of myriad indicators, from thermometers in weather stations to the migration of plankton, for it to be beyond dispute.

Right end of the telescope

The approach that scientists are using to greater and greater effect is to look at it from the other way round, and investigate the links from the climate change we know is happening to its individual manifestations.

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Most of Japan has sweltered. Image: CNN

So it was that just last week we saw the first scientific evidence that climate change increased the odds of the European heatwave.

That initial finding, widely reported in UK media and noted globally, suggested that the increase was ‘at least two-fold’ - although the researchers involved believe that after summer is over, when it’s possible to do a more comprehensive analysis involving a longer period of time and more weather data, the influence of climate change will turn out to be significantly more than that.

Event attribution science is moving quickly. Our Heavy Weather report showed last December that the number of studies is increasing all the time, with more than 40 scientific papers finding a link between climate change and specific extreme weather events published in just two years.

And the pace is set to quicken still further. As Quirin Schiermeier relates in Nature magazine this week, both Germany’s national weather forecaster and the European Centre for Medium-Range Weather Forecasting are developing new initiatives that will be able to perform event attribution studies in near-real-time.

Assuming they deliver, these will become amazing resources for many sectors of society; because rather than talking about the forecast impact of climate change on weather, we will able to talk about its actual impacts, more or less as they are happening.

Clarity not quantity

But it’s always going to be important to keep the attribution in the right direction.

Climate change may or may not have an impact on a specific weather event. But a specific weather event, even two or three together, does not ‘prove’ climate change – nor does it show ‘what climate change looks like’. After all, if part of the picture is increasing weather variability – which seems likely – then it’s always going to need a much broader look across years, regions and variations, to show ‘what climate change looks like’. Even then, it can only be a snapshot.

2018 won't be the hottest year ever; it's not likely to set any other climatic records either. So, while Europe’s having a big heatwave, and while climate change is implicated in that, let's also bear in mind the likely news at the end of the year.

Meanwhile we await attribution analysis for Algeria. And Japan. And Oman. And California. And wherever’s next in this violent summer.