A guide for journalists, written by climate scientists, sets out what reporters can say about the link between climate change and extreme weather events like heatwaves, storms and floods.
The guide, by researchers from Oxford University and Imperial College London and published by World Weather Attribution, an international group of climate scientists, explains how attribution science makes it possible to connect particular extreme events with climate change and why and where some events cannot always be linked with human-caused warming.
Until recently, scientists avoided connecting individual events with climate change, instead limiting themselves to saying that an event might reflect the sort of thing we can expect to see more of in the future if emissions and warming continue.
But scientists have developed methods that allow them to work out the link between climate change and an individual extreme weather event, calculating how much more or less likely, and how much more or less intense, an event has become because of global warming.
These attribution studies allow scientists to make statements like ‘this heatwave was three degrees hotter than it would have been in a world without global warming’, or even that an event would have been effectively impossible without climate change.
Even in the absence of a specific attribution study, journalists can often still make links between climate change and particular events. The guide sets out what journalists can say in these cases, covering heatwaves, floods, cyclones, snow, droughts and wildfires.
The guide says that ‘climate change cannot cause an event because all weather events have multiple causes, but climate change can affect how likely and how intense an event was’.
Among its conclusions are that every heatwave can now be linked with climate change and that both heavy rain and in some parts of the world — but not all — droughts are more common and more severe because of greenhouse gas emissions.
With some other types of extreme weather, there are other important factors journalists should be aware of when they describe the relationship with climate change.
‘Reporting extreme weather and climate change: A guide for journalists’ by Ben Clarke and Friederike Otto is available in nine languages at www.worldweatherattribution.org
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