Who is World Weather Attribution (WWA)?

The WWA initiative was formed in 2015 by Dr Geert Jan van Oldenborgh and Dr Friederike Otto. 

Today, the core WWA team is formed by researchers from several institutions, including the Grantham Institute – Climate Change and the Environment, Imperial College London, The Royal Netherlands Meteorological Institute, the Laboratoire des Sciences du Climat et de l’Environnement, and the Red Cross Red Crescent Climate Centre.

The core team also works with climate scientists and other experts in the country on which the study is being conducted, providing critical knowledge and insights on weather, databases, modelling and impacts.

Why are WWA studies performed rapidly?

Following an extreme weather event, people often ask: is climate change to blame?

Rapid attribution studies are carried out to give a robust, scientific answer to this question. 

The results are published days or weeks after the event to inform discussions about climate change, mitigation and adaptation, while the impacts of the extreme weather event are still fresh in the minds of the public and policymakers, and decisions about rebuilding are being made . 

How does WWA select extreme weather events to study?

WWA regularly monitors extreme weather events around the world. A range of criteria are used to decide if an attribution study should be carried out on a particular event. 

The criteria includes how many people are affected, how much damage has been caused and the declaration of a state of emergency or disaster.

A core team of WWA researchers meets once a week to discuss events that meet the criteria and decides if they can conduct a study on each event. 

The decision is based on the capacity of WWA researchers, the availability of local researchers who can contribute to the study, the availability of adequate data and whether a WWA study has been conducted in the country before.

What do WWA studies find out?

Each WWA study tries to answer three key questions:

  • How did climate change influence the intensity of the event?
  • How did climate change influence the likelihood of the event occurring?
  • How did pre-existing vulnerability worsen the impacts of the event?

The answers very much depend on the type of the event and the region in the world it occurs. In 2022 the team published a review paper describing what general lessons have been learned from conducting these studies. 

A summary of these findings is published as a guide to journalists in 12 languages. 

Why do WWA studies look at vulnerability and exposure?

Vulnerability worsens the impacts of extreme weather events. It is often what turns an extreme weather event into a disaster. 

For example, bad water management can increase the severity of a drought, faulty warning systems can slow evacuations in storms, homes built on low-lying land can be destroyed by floods, and a lack of green space in cities can further increase temperatures during a heatwave. 

Exposure refers to the people and assets, such as farmland and buildings, in an area affected by an extreme weather event.

WWA studies explore vulnerability and exposure in communities and countries to understand what actions may increase resilience to future extreme weather events.   

Are rapid WWA studies peer-reviewed?

While rapid attribution studies are published before peer review in order to release the results soon after events have taken place, many WWA studies are subsequently published in peer-reviewed journals. 

Scientific studies on extreme weather events, going through peer-review, are usually published months or even years after an event occurred, when the public has moved on and questions about responsibilities, rebuilding or relocating have been debated without taking scientific evidence on the influence of climate change into account.

WWA’s rapid attribution studies follow established methods, which have been peer-reviewed and assessed as scientifically reliable.

All WWA studies that have undergone peer-review have remained largely unchanged. Some examples include the 2016 floods in France, the 2017 study on Storm Desmond, the 2021 Madagascar drought and the 2022 Pakistan floods.

Where a WWA study has been peer-reviewed, a link to the academic paper is given in the sidebar of the analysis web page.

Are all extreme weather events made more likely and more intense by climate change?

While climate change is worsening many extreme weather events around the world, WWA studies occasionally find that climate change did not increase the likelihood and intensity of an event. 

These findings are important – they highlight places where disaster risk reduction measures should be improved to increase resilience to extreme weather, regardless of climate change. 

How much climate change influences a certain event very much depends on the type of the event and the region in the world where it occurs. In 2022 the team published a review paper describing what general lessons have been learned from conducting these studies. A summary of these findings is published as a guide to journalists, available in 12 languages. 

What can we say about an extreme weather event in the absence of an attribution study?

Attribution studies can’t be carried out for every extreme weather event, but thanks to other attribution studies and climate projections, scientists have a good understanding of the changes to different extreme weather events as our climate warms.

For example, we know that every heatwave in the world is now made stronger and more likely to happen because of human-caused climate change. 

For a more comprehensive overview of these changes, including changes to drought and storms, read our reporting extreme weather and climate change guide for journalists. 

Is attribution science new?

While the WWA has pioneered rapid attribution methods and applying them to extreme weather events, attribution science has been around for some time. 

Since the 1990s, understanding and quantifying the influence of human-induced climate change on global mean temperature  has been an important goal of the climate science community. For reaching this goal in the early 1990s the climate scientist Klaus Hasselmann was awarded the Nobel prize in physics in 2021.

In 2004, Stott et al., published a paper in Nature showing that climate change had at least doubled the risk of the record-breaking 2003 European summer heatwave that resulted in the deaths of tens of thousands of people. It was the first peer-reviewed published attribution study of an extreme weather event. 

Since 2012, attribution studies of extreme events have been performed for different weather events all over the world by researchers from many different countries. 

A database of the results of attribution studies that have been conducted on extreme events worldwide — more than 400 to date — is published at Carbon Brief.