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 climate change for their increasing severity? Join a live YouTube debate and ask your questions!

Public interest is often high after a heat wave, flood or drought, but can scientists really tell if a storm has been made worse by climate change, and how can the science of attribution of extreme weather events help them do so?

On March 23 at 14:00 (CET) our panel of experts will discuss the role that attribution of extreme weather events plays in educating the public about the connection between climate change and today’s weather.

And if global warming is not involved, then why did the catastrophe happen?

The panel of experts includes:

dr Frank Kreienkamp, ​​head of the Potsdam Regional Climate Office, German weather service DWD

dr Sonia Seneviratne, Professor of Land-Climate Dynamics, ETH Zurich

dr Sjoukje Philip, climate change researcher at the Dutch weather service KNMI

dr Jakob Zscheischler, group leader, Computational Hydrosystems department, Helmholtz Center for Environmental Research UFZ

dr Samantha Burgess, Associate Director of the Copernicus Climate Change Service

Jeremy Wilks, moderator

Submit a question to our panel using the form below:

What is the attribution of extreme events?

Extreme event attribution, an emerging field of climate science, analyzes whether extreme weather events such as heat waves, droughts or flash floods are caused by climate change. While scientists have studied extreme weather events for decades, due to the rigorous nature of scientific peer reviews, much of the research is not published in scientific journals until a year after the event.

Extreme event attribution was developed in 2003 and aims to change this and engage more widely with the media and the general public. Scientists have found that public interest wanes fairly quickly once an extreme weather event has passed. Therefore, to keep the public alert, it is vital that scientists provide quick answers on 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 and climate impact specialists from the Red Cross/Red Crescent Climate Center (RCCC). Although attribution of extreme events has been in development since 2003, it is only more recently that scientists have been able to provide definitive data on whether or not an event was caused by climate change.

WWA prioritizes the analysis of events that had a major impact on society so that its research reaches the widest possible audience and is useful for public debate.

How does WWA select the events to investigate?

While the WWA places its emphasis on weather events that have a major impact on society, these events are not always major events. Many of the extreme events they report are those for which the Red Cross/Red Crescent has issued an international appeal, although sometimes smaller events also garner intense media attention.

Examples of extreme weather events the group has studied include the record-breaking rains brought on by Storm Desmond in the UK in 2015, the drought in Somalia in 2016 and the heatwave in Siberia in 2020. To maximize impact, the WWA try to respond to media and public questions in their work.

How does WWA analyze extreme weather events?

Once an extreme weather event has been selected, the WWA team reviews the relevant metrics and works with on-site experts where possible.

Ultimately, the WWA is trying to determine whether an extreme weather event is due to human-caused climate change as a result of burning fossil fuels, or in part the nature of the event they are analyzing.

For heatwaves, they look at temperature or wet-bulb temperature when humidity is involved, but they do not analyze 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 conditions.

For example, since European countries introduced heat plans after the heat waves of 2003 and 2006, the number of deaths per heat degree has decreased. Since this data is constantly changing, it is too complex to be collected meaningfully.

However, when analyzing the impact of an event, the exact dates may also vary depending on the needs and activities of the local population. In agricultural communities where the population works mostly outdoors, the WWA uses the local highest daily high temperature of the year to measure the health risk, while in societies where most people work indoors they found that a 3- Daily average temperature more useful is their analysis.

The importance of climate models in analyzing extreme weather events

However, relying on temperature and meteorological observations alone is not sufficient to determine whether an extreme weather event is linked to climate change.

To get a more complete picture, WWA scientists use climate models to simulate weather patterns — the same way weather models predict weather for the coming days. These climate models are used to predict the likelihood and regularity of extreme weather events. This data is then compared to real-world observations to see if the two are compatible.

So is climate change to blame for extreme weather events?

While the media often wants 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 also caused by other types of human behavior.

For example, some heat waves are caused in part by land-use change, such as logging and land clearing, where previously trees and plants cooled the air through evaporation.

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

Analyzing a cold April 2021, which followed an unusually warm March and resulted in significant frost damage to central France’s grape crop, analysts discovered a mixed picture.

While the team concluded that anthropogenic climate change had made the weather event 20 to 120 percent more likely, they also discovered that April’s temperature would actually have been about 1.2 degrees Celsius lower had it not been for human-caused climate change.

Crucially, however, climate change had resulted in an earlier occurrence of bud burst on the vines, meaning the young leaves were exposed to lower temperatures during frosts, leading to more frost damage.

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

By preparing its reports as quickly as possible after an extreme weather event, WWA aims to make them available to the public while the event is still being widely discussed. In doing so, the initiative hopes to raise awareness of the role climate change is playing in global weather patterns.

Meet our panelists:

dr Frank Kreienkamp, ​​head of the Potsdam Regional Climate Office, DWD

dr Frank Kreienkamp is head of the Potsdam Regional Climate Office at the German Weather Service. He specializes 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 of Land-Climate Dynamics, ETH Zurich

Sonia Seneviratne is Full Professor of Land-Climate-Dynamics at ETH Zurich. She is a climate scientist and environmental physicist. After completing her bachelor’s and master’s degrees at the University of Lausanne and ETH Zurich, she received her doctorate in climate science from ETH Zurich in 2003.

She has been coordinating lead author and lead author of several IPCC reports, including the IPCC Special Report on 1.5°C Global Warming (2018).

dr Sjoukje Philip, Climate Change Researcher, KNMI

With a background in geophysics, Sjoukje Philip started working at KNMI in 2015 in the field of rapid attribution of (weather) events. She works on the rapid analysis of extreme weather events, including creating “trigger schemes” to accurately predict how many people will be affected.

dr Samantha Burgess, Associate Director of the Copernicus Climate Change Service

dr Samantha Burgess is Deputy Director of C3S, the European Union’s Copernicus Climate Change Service, and works to improve understanding of climate-related risks. C3S offers open access to climate data worldwide to make better decisions. Sam has previously focused on environmental resilience, sustainable finance and ocean governance in positions such as chief scientific adviser and policy leader in government, business, NGOs and academia.

dr Jakob Zscheischler, group leader, Department Computational Hydrosystems, UFZ

Jakob Zscheischler is an Earth system scientist with a background in mathematics, biogeochemistry and climate science. His research focuses on composite weather and climate events. Jackob chairs the European COST action DAMOCLES (Understanding and Modeling Compound Climate and Weather Events, CA17109), which brings together climate scientists, engineers, social scientists, impact modelers and policy 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. It has been reporting on scientific 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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