• 14 July 2017

Visualising extreme weather events around the world: are they linked to climate change?

Carbon Brief's interactive map: attributing extreme weather to climate change

A new map showing how climate change is affecting extreme weather is making the rounds on social media after the Carbon Brief published it on 6th July.

The map visualises more than 140 extreme weather event studies from around the world and suggests that 63% of the analysed extreme events were found to be more likely or more severe due to climate change.

Linking weather events to climate change is a growing science, and one that ECI plays a prominent role in through the World Weather Attribution project and several other research projects using the distributed computing framework climateprediction.net. Our involvement in extreme weather attribution spans back to the initial Nature paper co-authored by Dr Myles Allen in 2004 which suggested that climate change had doubled the risk of the 2003 European heatwave. Since then we have led, and been involved in, many subsequent event studies, and methodological papers looking at the science itself. Dr Friederike Otto now leads the team at Oxford.

Talking about the map, Dr Friederike Otto said: 'This map is a very useful resource for both scientists and practitioners. It could become a very useful tool for decision makers looking for scientific evidence to better prepare and adapt to extreme weather events'.

The map gives a clear visual picture of the three distinct outcomes of the studies: that the event is more or less likely under climate change (orange); that the likelihood of the event has not changed (yet) under climate change (blue); and that there is not enough evidence to draw any robust conclusions (grey). However Otto adds that an absence of evidence 'doesn't necessarily mean there wasn't a human influence, just that a particular analysis didn’t find one.' She explains that this is why a single study should never be considered the final word on how climate change affects a given type of extreme weather. It is important that an honest picture is presented if no influence is found, because this has implications for decision makers. (More can be read on this in a Conversation piece co-authored by Otto)

The strongest relationship with extreme weather and climate change across the studies was in relation to heat, where 85% of studies found that climate change had made an event more likely or more severe. For flooding cases the link was lower, at 45%. This shows that there are differences notable between the types of events.

'Looking at the findings, the map highlights that not all extreme weather events are getting worse, but that the impact of climate change on extreme weather is very different depending on the type of events, as well as the region and season it occurs.' Said Otto.

While the evidence is mounting, there are limitations in the spread of studies presented in the map, which are far from random and by no means representative of all extreme weather events that have occurred. Thus the map cannot be assumed to give an overview of the impact of climate change on all extreme weather events. 'These events are usually studied because they happened in the backyard of the researchers or got high media attention but are certainly not a random sample.' Explains Otto.

"This map is a very useful resource for both scientists and practitioners. It could become a very useful tool for decision makers looking for scientific evidence to better prepare and adapt to extreme weather event”

Dr Friederike Otto

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