When can we blame climate change? The tricky science of attribution

When can we blame climate change? The tricky science of attribution

Extreme weather events are increasing in many parts of the world, but can we always blame their mounting severity on climate change? Join us for a live YouTube debate, and ask your questions!

In the aftermath of a heatwave, flood or drought, public interest is often intense, but can scientists really pinpoint whether a storm was made worse by climate change, and how can the science of extreme weather event attribution help them to do so?

At 2pm (CET) on 23 March our panel of experts will discuss the role that extreme weather attribution plays in educating the public about the link between climate change and today’s weather.

And if global warming isn’t involved, then why did the disaster happen?

The expert panel will include:

Dr. Frank Kreienkamp, Head of the Regional Climate Office PotsdamGerman weather service DWD

Dr. Sonia Seneviratne, Professor for Land-Climate Dynamics, ETH Zürich

Dr. Sjoukje Philip, Researcher in Climate Change, Climate Change at Dutch weather service KNMI

Dr. Jakob Zscheischler, Group Leader, Department of Computational Hydrosystems,Helmholtz Centre for Environmental Research UFZ

Dr. Samantha Burgess, Deputy Director of the Copernicus Climate Change Service

Jeremy Wilks, Moderator

Submit a question to our panel using the form below:

What is extreme event attribution?

An emerging field of climate science, extreme event attribution analyses whether extreme weather events, such as heatwaves, droughts or flash flooding, are caused by climate change. While scientists have been looking at extreme weather events for decades, due to the rigorous nature of scientific peer review, much of the research isn’t published in scientific journals until a year after the event.

Developed in 2003, extreme event attribution aims to change this and engage more widely with the media and the general public. Scientists have discovered that once an extreme weather event passes, public interest begins to drop off quite quickly, so in order to keep the public’s attention, it is vital that scientists offer quick answers about the causes of an extreme event.

Founded in 2014, The World Weather Attribution Initiative (WWA) is a collaboration of scientists from the UK, Netherlands, France, USA, Switzerland and India, along with climate impact specialists from the Red Cross/Red Crescent Climate Centre (RCCC). Although extreme event attribution has been in development since 2003, it is only more recently that scientists have been able to provide definitive data on whether an event is caused by climate change or not.

The WWA prioritises the analysis of events that have had a large impact on society in order for their research to reach as large an audience as possible and be useful for public debate.

How do the WWA choose which events to study?

While the WWA put their emphasis on weather events which have had a big impact on society, these events aren’t always big ones. Many of the extreme events they cover are ones for which the Red Cross/Red Crescent has issued an international appeal, though sometimes smaller events attract intense media attention too.

Examples of extreme weather events that the group have studied include the record-breaking rainfall caused by Storm Desmond in the UK in 2015, the Somalian drought of 2016, and the Siberian heatwave of 2020. In order to have as big an impact as possible, the WWA try to respond to questions posed by the media and the public in their work.

How does WWA analyse extreme weather events?

Once an extreme weather event has been selected, the team at WWA look at the relevant metrics and work with local experts if they can.

Ultimately, the WWA is trying to find out whether an extreme weather event is due or partly due to human-induced climate change as a result of burning fossil fuels.To find this out, the team uses a number of different data sources, depending on the type of event they are analysing.

For heatwaves, they look at temperature, or wet bulb temperature if humidity is involved, but they do not analyse the number of deaths caused by the event. This is because this data is much less reliable, and tends to change as societies adapt to extreme weather.

For example, since European countries introduced heat plans after the 2003 and 2006 heatwaves, the number of deaths per degree of heat have decreased. As this data is always changing, it is too complex to be captured in a meaningful way. 

However, when it comes to analysing the impact of an event, the exact data used can also vary depending on the needs and activities of the local population. In agricultural communities, where populations mostly work outdoors, the WWA uses the local highest daily maximum temperature of that year to measure health risk, while in societies where most people work indoors, they have found that a 3-day mean temperature is more useful for their analysis.

The importance of climate models in analysing extreme weather events

Relying on temperature and meteorological observations on their own though is not enough when it comes to determining whether an extreme weather event is linked to climate change.

In order to get a fuller picture, the scientists at WWA use climate models to simulate weather patterns – in the same way that weather models predict the weather for the days ahead. These climate models are used to predict the likelihood and regularity of extreme weather events. This data is then compared to real life observations to see whether the two are compatible.

So, is climate change to blame for extreme weather events?

While the media often want a definitive answer, the facts are usually more complex. When it comes to extreme weather, the WWA has found very clear links between heatwaves and climate change, but not all heatwaves are caused by climate change – many are caused by other types of human behaviour too.

For example, some heatwaves are partly driven by land use changes, such as logging and land clearance, where previously there had been trees and plant life that cooled the air through evapotranspiration.

The WWA has also found significant climate change trends in cold weather extremes, but even here the story is complex, and shows how delicately balanced our ecosystems are.

In an analysis of the cold April of 2021, which had followed an unusually warm March and led to significant frost damage in the grape crop of central France, the analysts discovered a mixed picture.

While the team concluded that anthropogenic climate change had made the weather event 20 to 120 per cent more likely, they also discovered that without human-caused climate change, the temperature in April would have actually been approximately 1.2 degrees Celsius lower.

Crucially though, climate change had led to an earlier occurrence of bud burst on the grapevines, which meant that when the frost hit, the young leaves were exposed to lower temperatures, leading to more frost damage.

How does this data help the public to better understand climate change?

By producing their reports as quickly as possible after an extreme weather event, the WWA aims to make it available to the public while the event is still being widely discussed. By doing so, the initiative hopes to raise awareness of the role that climate change is having on global weather patterns. 

Meet our panellists:

Dr. Frank Kreienkamp, Head of the Regional Climate Office Potsdam, DWD

Dr Frank Kreienkamp is Head of the Regional Climate Office, Potsdam at the Deutscher Wetterdienst (the National Weather Service of Germany). He specialises in the statistical analysis of climate change, including changes in extremes and the process of communicating these results to politicians, administrations and the general public.

Dr. Sonia Seneviratne, Professor for Land-Climate Dynamics, ETH Zurich

Sonia Seneviratne is Full Professor for Land-Climate Dynamics at ETH Zurich. She is a climate scientist and environmental physicist. After her undergraduate and graduate studies at the University of Lausanne and ETH Zurich, she was awarded her PhD thesis in climate science in 2003 at ETH Zurich.

She was a Coordinating Lead Author and Lead Author on several IPCC reports, including the IPCC Special Report on 1.5°C Global warming (2018).

Dr. Sjoukje Philip, Researcher in Climate Change, KNMI

With a background in geophysics Sjoukje Philip began working at KNMI in 2015 in the field of rapid (weather) event attribution. She works on the rapid analysis of extreme weather events, including creating ‘trigger schemes’ to accurately predict how many people have been impacted.

Dr. Samantha Burgess, Deputy Director of the Copernicus Climate Change Service

Dr Samantha Burgess is Deputy Director of C3S, the European Union’s Copernicus Climate Change Service, working to improve understanding of climate related risks. C3S provides open access to climate data globally to inform better decisions-making. Sam has previously focused on environmental resilience, sustainable finance & ocean governance in roles including chief scientific advisor & head of policy in government, in business, NGOs and academia.

Dr. Jakob Zscheischler, Group Leader, Department of Computational Hydrosystems, UFZ

Jakob Zscheischler is an Earth system scientist with a background in mathematics, biogeochemistry and climate science. His research focuses are compound weather and climate events. Jackob is the Chair of the European COST Action DAMOCLES (Understanding and modeling compound climate and weather events, CA17109), which brings together climate scientists, engineers, social scientists, impact modellers and decision-makers and coordinates national research projects on compound events.

Jeremy Wilks, Moderator

Euronews science reporter Jeremy Wilks covers everything from climate change to healthcare innovation. He has reported on science research, innovation and digital technology across Europe for over a decade. Jeremy is the presenter of the monthly Climate Now series on Euronews and presents the new Ocean Calls podcast.


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