Scientists are finally linking extreme weather to climate change
Until now scientists have been cagey about linking extreme weather events such as this summer’s heatwave to climate change. An emerging field is changing all that.
Patrik Stollarz/AFP/Getty Images
The summer of 2018 has not been a normal summer.
Throughout June and July an extended heatwave set record-breaking high temperatures across the northern hemisphere.
In Japan, more than 22,000 people were taken to hospital with heat stroke as the country recorded its highest-ever temperature of 41.1 degrees Celsius.
In California, Portugal and as far north as the Arctic Circle huge wildfires, encouraged by months of unusually dry conditions, followed the searing heat.
For years, climatologists asked to explain these kind of extreme events have fallen back on a well-worn phrase. “It’s impossible to attribute a single weather event to climate change,” the refrain goes. And they’re right.
Weather is by its very nature unpredictable – extreme events will always happen in one place or another, regardless of global temperature levels, and they’re not necessarily tied to one particular cause.
For Friederike Otto, deputy director of the Environmental Change Institute (ECI) at the University of Oxford, this response has its drawbacks. “If scientists don’t answer, someone else gives an answer and it’s usually people who aren’t interested in the size and have their own agenda,” she says. Instead, Otto wondered if scientists could start saying whether climate change had made certain extreme weather events more or less likely.
Now Otto is right at the heart of a growing scientific movement called extreme event attribution.
Her aim?
To be able to point to an extreme weather event and use climate modelling to say whether that same event would have been more or less likely to happen in a world where humans hadn’t caused global temperatures to rise by a whole degree over the last 120 years.
Up until a few years ago, it wasn’t possible to draw that link with any degree of accuracy, Otto says. But in 2004, Pete Stott at the UK Met Office published a paper in the scientific journal Nature showing that climate change had at least doubled the risk of the 2003 European heatwave that killed tens of thousands of people.
Twelve years later the Bulletin of the American Meteorological Society dedicated an entire issue to the new field of extreme event attribution.
In the introduction, its editors argued that it was now possible to detect the effects of climate change on some events with high confidence. “That was really the first time we could say that we can attribute events to anthropogenic climate change,” Otto says.
In late 2014, Otto helped set up the World Weather Attribution (WWA) initiative – a collaboration between the ECI, the Netherlands-based Red Cross Red Crescent Climate Centre and Royal Netherlands Meteorological Institute.
The aim of the project wasn’t just to draw a link between extreme events and climate change, but to provide this analysis in real-time so they’d have answers while the extreme weather event was actually happening.
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