By AFP - Agence France Presse
The pioneering science linking climate to weather disasters
Julien MIVIELLE
Extreme weather is becoming more destructive as the world warms up, but how can we say that climate change has intensified the fires in Los Angeles, the typhoons in the Philippines, or the floods in Spain?
That question was once difficult to answer. But thanks to the pioneering field of attribution science, experts can quickly examine the possible influence of global warming on a specific weather event.
This fast-growing field began two decades ago and is now firmly established, but is still sometimes hampered by a lack of data.
- Real-world impact
After a disaster has occurred, an attribution study can quickly help inform governments, industry, and ordinary people whether climate change has played a role.
“It's important for citizens, for decision-makers and it's also very important for scientists because, with each case study, we learn new things about our models, our observations, and the problems we encounter with them,” said Robert Vautard, one of the leading scientists on the UN panel of climate experts, which has supported the development of attribution studies.
In the future, these studies could also play an increasing role in legal disputes.
A scientific study from 2021 has already been used by a Peruvian farmer in his battle against German electricity giant RWE, which he accused of playing a role in the melting of a glacier.
This research concluded that the retreat of the glacier was “entirely attributable” to global warming.
- Different approaches
The main questions that attribution studies seek to answer are: has the warmer climate made a flood, heatwave, fire, or storm more likely, and has it increased its ferocity?
Various groups have developed methods that have been independently validated by other researchers.
The most active and influential group of researchers is World Weather Attribution (WWA), whose work is frequently reported in the media.
Using computer models, scientists can compare a simulation of a given climate event with a world in which warming caused by the burning of fossil fuels and other human activities was not present.
In their most recent study, WWA researchers found that climate change has increased the risk of wildfires in Los Angeles, which have killed at least 29 people and destroyed more than 10,000 homes since they began on January 7.
According to the researchers, the conditions that fueled the fires were approximately 35% more likely due to global warming caused by the burning of fossil fuels, reducing rainfall, drying out vegetation, and amplifying the overlap between flammable drought conditions and strong Santa Ana winds.
Other organizations that carry out attribution studies include Britain's Met Office, which also compares the current climate with simulations of a world with a climate more similar to that before the Industrial Revolution.
However, others use more comprehensive techniques, including ClimaMeter, which describes itself as “a rapid experimental framework for understanding extreme weather events”.
The group uses historical observation data rather than more complex computer models, as well as news reports and AI tools such as ChatGPT, although it admits that its method is less effective in analyzing very unusual events.
- No single cause
The scientists emphasize that climate change should not be considered the sole cause of an extreme event and its impacts.
“For example, if an inveterate smoker develops lung cancer, we wouldn't say that cigarettes caused the cancer, but we could say that the damage caused by cigarettes made the cancer more likely,” explains the WWA on its website.
The researchers also analyze the political or social factors that make a climate disaster more deadly or destructive - shoddy construction, for example, or poorly maintained infrastructure.
Some types of extremes have a well-established link to climate change, such as heat waves or heavy rains.
“More and more, we are starting to have events that we can clearly say would have an almost zero probability without our influence on the climate,” said Sonia Seneviratne, a climate scientist who has worked with the WWA.
“Events are now becoming so extreme that it is easier to detect this influence,” she notes.
Other phenomena, such as droughts, snowstorms, tropical storms, and forest fires, can result from a combination of factors and are more complex.
- Searching for data
Another limitation that worries researchers is the scarcity of observational data and measurements in certain parts of the world, especially in Africa.
This scarcity makes it difficult to study the impacts, leading to inconsistencies between different analyses.
“The lack of observed data is penalizing in certain regions. There is also a lack of model data, i.e. high-resolution climate simulations,” said Aurelien Ribes, a climate scientist at the French meteorological research agency CNRM.
He emphasized the need for consistency and said that “any future use of this data in legal or compensation proceedings will have to be based on more systematic approaches.”
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