Climate enforcers need hard evidence, and Friederike Otto has it

World Weather Attribution provides crucial leverage for legal and policy battles.

On July 19, 2022, the UK experienced a taste of the weather to come. Temperatures reached 40.3° Celsius—soaring past the previous record by more than one-and-a-half degrees.

Dozens of homes in east London were destroyed by fires, while elsewhere in the country, the heat pushed the power grid close to the point of failure. The Office for National Statistics estimates that there were more than 2,800 excess deaths among over-65s during the summer heat waves of 2022, making it the deadliest year for heat since 2003.

Before the temperatures had even peaked, Friederike Otto was in her office in Imperial College London, getting ready to answer the question that she knew would be thrown at her countless times in the following week: Was climate change to blame?

When an extreme weather event strikes, Otto and her small team of climate scientists—most of them working in their spare time—are the people the world looks toward to tell them whether climate change has made the weather more severe or more likely to be. “I think it’s important to get a more realistic picture of what climate change means,” says Otto, a senior lecturer in climate science at the Grantham Institute for Climate Change and the cofounder of the World Weather Attribution initiative. “For some types of events, like heat waves, climate change is a real game-changer, and we see events that we have never seen before.”

Every week, a contact at the Red Cross sends Otto and her colleagues at World Weather Attribution a list of floods, heat waves, and other extreme weather events across the globe. Often there are six or eight crises listed in the email—far too many for Otto’s small team to tackle—so the scientists narrow their focus to weather that is impacting millions of people, selecting roughly one event every six weeks, from storms in Europe to flooding in Pakistan.

Once the scientists have picked a subject for their analysis, they move fast, digging into historical records and running climate models in order to figure out what role—if any—climate change played in a disaster. The final report is usually published within days or weeks of an extreme weather event. This is a huge departure from the normally glacial pace of academic publishing, where it can take years for a scientific paper to finally end up in a journal, but quick answers are the whole point of World Weather Attribution. By releasing studies while an extreme event is still dominating headlines and political agendas, the scientists fill a void that might otherwise be occupied by climate change denial. In the case of the UK heat wave, World Weather Attribution was ready with its report just nine days after temperatures reached their peak.

The findings revealed the unprecedented scale of the record-breaking temperatures. Otto’s team estimated that climate change had made the UK heat wave at least 10 times more likely, and that in a world without global warming peak temperatures would have been about 2° Celsius lower. The weather was so unusual that, in a world without climate change, it would have been statistically impossible to reach such high temperatures in two out of the three weather stations the scientists studied. In the world of climate attribution science, this is about as close as you get to a smoking gun. “People always want the number, and sometimes you can’t give a very satisfactory number,” Otto says. This time, however, Otto had no shortage of numbers to share with the reporters who were ringing her up.

But attribution science can do a lot more than tell us how climate change influences the weather. Otto wants to use her attribution reports to hold polluters to account for extreme weather events. “We have started to do a lot of work with lawyers, to basically bridge this knowledge gap between what we can say scientifically and what has so far been used in terms of evidence,” she says. With legal cases underway in Germany and Brazil, attribution science is moving into the courtroom.

The beginnings of WWA

Otto cofounded World Weather Attribution in 2014 with the oceanographer Heidi Cullen and climatologist Geert Jan van Oldenborgh. At first, Otto—who has degrees in physics and philosophy—thought that the main role of weather attribution was to untangle the complexity of weather systems to quantify how much climate change was influencing extreme weather. Other scientists had established how to use climate models to attribute weather events to climate change, but no one had tried to use the science to produce rapid 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 followed on floods, storms, and rainfall, each one published within weeks of the disaster. But attribution studies aren’t just about understanding past events—they can help us prepare for the future, Otto says. “I see attribution now as a tool that helps us disentangle drivers 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 one example of this. Otto and her colleagues agonized over the wording of their report, as there were so few similar events in the historical records that their models struggled to simulate the extreme rainfall accurately. They knew that rainfall in the area was much more intense than in the past, but they couldn’t put a firm number on how much of that increase was due to climate change. “It could be that all of it is climate change, but it could be that [the role of] climate change is much smaller,” Otto says. Even though the cause couldn’t be pinpointed, the report highlighted just how vulnerable Pakistan is to severe flooding, highlighting the proximity of farms and homes to flood plains, poor river management systems, and poverty as major risk factors. “Vulnerability is what makes the difference between an event having basically no impact or it being a catastrophe,” says Otto.

World Weather Attribution’s work tends to make headlines when it concludes that climate change makes extreme weather more likely, but the opposite result can be even more useful to regions facing disasters. One investigation into a long drought in southern Madagascar found that the chance of low rainfall hadn’t significantly increased due to human-induced climate change. Knowing this gives agency back to countries, says Otto. “If you think it’s all to do with climate change, then there’s nothing you can do unless the global community gets its act together. But if you know that climate change is not actually playing a big role, or none at all, then that means everything you do to reduce your vulnerability actually makes a huge difference.”

Taking it to court

It’s not only governments that are extremely interested in the results of attribution studies. Courts are starting to pay attention, too. In August 2021, an Australian court ruled that the New South Wales Environment Protection Agency had not fulfilled its duty to protect the environment from climate change, in a case brought by bushfire survivors. One of Otto’s attribution studies into the 2019-20 bushfire season was used in a report commissioned by the court, but she found out about it only when one of the lawyers involved in the case emailed her after the verdict had been declared. “This is really nice to see, when a study that we did has real-world impact,” she says.

If attribution studies can tell us that a disaster was made more severe because of climate change, they also point toward something else: Who might be held responsible. Richard Heede, a geographer from California, has spent decades delving through archives to estimate companies’ carbon emissions all the way back to before the Industrial Revolution. The result is known as the Carbon Majors: a database of the world’s biggest polluters up to the present moment. The 2017 Carbon Majors report found that half of all industrial emissions since 1988 could be traced to just 25 corporate or state-owned entities. The state-owned fossil fuel firm Saudi Aramco alone is responsible for 4.5 percent of the world’s industrial greenhouse gas emissions between 1988 and 2015.

This data is extremely useful for people trying to bring legal cases against fossil fuel firms. In May 2022, a group of scientists and lawyers traveled to the Peruvian Andes to inspect a giant glacier that looms over the crystalline waters of Lake Palcacocha. If the glacier collapses into the lake, scientists fear it could submerge the nearby city of Huarez. Peruvian farmer Saúl Luciano Lliuya thinks that polluters should foot the cost of defending the city from floodwater as global warming has shrunk glaciers around Lake Palcacocha, increasing the risk of dangerous flooding. The target of the lawsuit is the German energy firm RWE, which was responsible for 0.47 percent of all industrial greenhouse gas emissions between 1751 and 2010, according to Heede’s data. Lliuya is suing for just 14,250 pounds ($17,170)—that’s 0.47 percent of the cost of protecting Huaraz.

If Lliuya wins the case, it could set a precedent that polluters can be held legally responsible for the effects of their emissions anywhere on the planet. “That would really change this narrative that we’re operating in,” Otto says. It would also make the work of weather attribution even more critical. If scientists know that climate change had made flooding in an area twice as severe as it would have been, for example, they can use that evidence to estimate how much individual companies and states contributed to that disaster. One of Otto’s students is already working on a legal case in Brazil that involves weather attribution. “We have seen a huge interest in that. It’s not just journalists calling and wanting to know, but also lawyers,” Otto says.

Despite the booming interest in the field, World Weather Attribution is still almost entirely run by scientists working for free in their spare time. Eventually, Otto hopes that the task of weather attribution could become a routine part of weather services, which would give her more time to focus on the science of hurricanes and droughts, which are much more difficult to analyze. But for now, her main focus is making her attribution studies more useful to lawyers and helping achieve some justice for the people most affected by climate change. “Climate change will never be a catastrophe for those who are rich. And I think that’s why it’s ultimately a justice issue, because those who pay are the ones who are the most vulnerable in society.”

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