Climate enforcers need hard evidence. Friederike Otto has it

But attribution science can do much more than tell us how climate change affects weather. Otto wants to use her attribution reports to hold polluters accountable for extreme weather conditions. “We started working a lot with lawyers, to basically bridge this knowledge gap between what we can say scientifically and what has been used so far in terms of evidence,” she says. With lawsuits pending in Germany and Brazil, attribution science is entering the courtroom.

OTTO CO-FOUNDED World Weather Attribution in 2014 with oceanographer Heidi Cullen and climatologist Geert Jan van Oldenborgh. Initially, Otto, who has a degree in physics and philosophy, thought that the main role of weather attribution was to untangle the complexity of weather systems in order to quantify how much climate change affected extreme weather events. Other scientists had determined how to use climate models to attribute weather events to climate change, but no one had tried to use science to quickly produce reports on recent disasters.

World Weather Attribution’s first real-time study was published in July 2015. It found that a heat wave in Europe earlier that month was almost certainly made more likely thanks to climate change. Other studies on floods, storms and rainfall followed, all of which were published within weeks of the disaster. But attribution studies aren’t just about understanding past events, they can help us prepare for the future, says Otto. “I now see attribution as a tool that helps us untangle the causes of disasters and helps us use extreme events as a lens in society to see where we are vulnerable.”

Pakistan’s devastating 2022 monsoon season is an example of this. Otto and her colleagues were concerned about the wording of their report because there were so few similar events in the historical accounts that their models struggled to accurately simulate the extreme rainfall. They knew rainfall in the area was much more intense than in the past, but they couldn’t give hard numbers on how much of that increase was due to climate change. “It could be that it’s all climate change, but it could be [the role of] climate change is much smaller,” says Otto. While the cause could not be determined, the report highlighted how vulnerable Pakistan is to severe flooding, highlighting proximity of farms and homes to flood plains, poor river management systems and poverty as major risk factors. “Vulnerability makes the difference between an event that has essentially no impact or a catastrophe,” says Otto.

World Weather Attribution’s work often makes headlines when it concludes that climate change is making extreme weather events more likely, but the opposite result could be even more useful for regions facing disasters. A study of a prolonged drought in southern Madagascar found that the likelihood of low rainfall had not increased significantly due to human-induced climate change. Knowing this gives countries a say again, says Otto. “If you think it’s all about climate change, then there’s nothing you can do unless the global community gets its act together. But if you know that climate change doesn’t really play a big role, if at all, it means that everything you do to reduce your vulnerability does make a huge difference.”

Photo: Maria Lax

IT’S NOT ALONE governments that are very interested in the results of attribution studies. Courts are also starting to take notice. In August 2021, an Australian court ruled that the New South Wales Environment Protection Agency had failed in its duty to protect the environment from climate change, in a case brought by bushfire survivors. One of Otto’s attribution studies into the 2019-2020 wildfire season was used in a court-commissioned report, but she didn’t find out until one of the attorneys involved in the case emailed her after the verdict was handed down. “This is really nice to see, when a research we’ve done has an impact in the real world,” she says.

If attribution studies can tell us that a disaster has become more serious due to climate change, they also point to something else: who can be held responsible. Richard Heede, a California geographer, has spent decades sifting through records to estimate corporate carbon emissions before the industrial revolution. The result is known as the Carbon Majors: a database of the world’s largest polluters to date. The Carbon Majors 2017 The report found that half of all industrial emissions since 1988 could be traced to just 25 corporate or state-owned companies. The state-owned fossil fuel company Saudi Aramco alone is responsible for 4.5 percent of global industrial greenhouse gas emissions between 1988 and 2015.

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