The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, engineering, and medicine. They operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln. This week, the organization published a report that claims attribution science — which seeks to define the connection between human activity and alterations in the climate — has made great strides forward since the last report a decade ago. That report backs a growing body of scientific knowledge that could help governments hold oil, gas, and coal companies responsible for the damage caused by extreme weather. Known as extreme event attribution (EEA), it seeks to answer an increasingly common question — how much was the latest heat wave, downpour, drought, or wildfire made worse by climate change? Scientists have long understood that global warming, driven by greenhouse gas emissions from the burning of fossil fuels, is making certain kinds of extreme weather more intense and more likely. But only in the past two decades have they developed the tools for estimating precisely how much worldwide warming is shaping particular weather events in particular places. The new report does not make recommendations for how attribution science should be used in policy and legal settings, though it notes that attribution findings could be relevant in several types of legal cases. In a $50 billion lawsuit against several oil companies, Multnomah County in Oregon cited an attribution study that concluded a record shattering 2021 summer heat wave in the Pacific Northwest would have been “virtually impossible” without human-caused climate change. For its part, the National Academy says confidence in extreme event attribution studies varies significantly across different types of extremes. The highest confidence is associated with findings for extreme heat and cold events and other events strongly influenced by a warming atmosphere, such as large-scale heavy rainfall events like those happening in Texas this week where the Guadalupe River rose 25 feet after heavy rain. Is that extreme enough for you? Confidence is lowest for phenomena where observational records are limited and for phenomena that depend on small-scale dynamic processes that are inadequately reflected in global climate models, such as severe convective storms like thunderstorms and tornadoes. Forward Progress “Significant progress has been made over the last decade, with major advancements in methods and modeling that allow for more robust assessments of extreme events,” said James Hurrell, chair of the committee that wrote the report and a professor of environmental science and engineering at Colorado State University. “But the field still faces challenges, and addressing them is necessary to fully realize the value of attribution science. We hope our recommendations will guide those efforts.” Scientists are now able to move beyond detecting broad trends and begin investigating how climate change influences individual extreme events, yielding information that can help people better understand the role of climate change in local weather events so that knowledge can be incorporated into their own planning and policy. EEA studies compare the observed event’s characteristics — such as its likelihood and intensity in the current climate — with a “counterfactual” world without human-caused emissions. Researchers use a combination of observational data, weather and climate models, and statistical models to make these comparisons and quantify the effect of climate change on the extreme event. Radar, satellite, and on-site observations have expanded in terms of area and length of time covered, resulting in additional data to support EEA analyses for many regions. Also, the use of larger climate model simulations is making it possible for researchers to more effectively separate the human-caused climate signal from natural variability. Better Data The National Academies report finds that researchers’ methods for extreme event attribution have advanced “considerably” in recent years. Scientists are using more sophisticated techniques and better data, the report says. That is helping them assess with greater confidence how much the searing temperatures during a particular hot spell, for instance, can be attributed to human activity as opposed to routine randomness in the atmosphere. Pinpointing the influence of human-caused warming remains a challenge for some kinds of unruly weather, the report notes, including tornadoes and hail storms. And many developing nations lack the long-term weather records that would help scientists make confident attributions about events there, the report says. “Attribution science is still relatively new, and I think we have made a lot of progress,” said Jim Hurrell. “I think there’s room for accelerating that progress even further.” Scientists have several methods for evaluating how much human-caused warming contributed to a particular weather event. Using computer models of the climate, they can estimate the likelihood of similar events in a hypothetical world that industrialized nations hadn’t warmed by emitting heat-trapping gases. They can scour historical records for past instances in which atmospheric patterns lined up a certain way, then examine how much hotter or rainier the weather was when those same patterns appear today. Some researchers are trying to go further. They want to estimate not just how much hotter a given heat wave was because of climate change, but how much deadlier. Not just how much more rain a hurricane delivered, but how much more damage to homes and infrastructure it caused. One Step Forward, Two Steps Back Allies of the fossil fuel industry have attacked scientists who conduct attribution analyses. This week, Energy in Depth, a project of the Independent Petroleum Association of America, a lobbying group, suggested that the National Academies report should be seen as “the latest deliverable in a well-funded litigation campaign.” When asked about accusations of bias against fossil fuels, Dr. Hurrell noted that the National Academies checks the authors of its reports for potential conflicts of interest and that its reports are reviewed by another set of experts before being issued. “I think it’s a very objective assessment,” he said. Last fall, as the administration was working to rescind the endangerment finding — a scientific determination underpinning the federal government’s authority to regulate greenhouse gas emissions — a report by the academies defended the finding’s accuracy. It is “beyond scientific dispute,” the report said, that such emissions are harming human health and well being. The administration revoked the finding anyway. After the putative president canceled an assessment on the health of nature in the United States, the authors compiled the report independently, and the National Academies reviewed it. The final report is slated for release this fall. The new report on extreme event attribution was prepared by a committee of 14 scholars representing meteorology, law, sociology, civil engineering, and other disciplines. It is an update to a previous National Academies report that examined attribution science in 2016, when it was still a nascent field. The committee’s work was sponsored by the National Science Foundation; the National Oceanic and Atmospheric Administration; the Bezos Earth Fund; and the Heising-Simons Foundation, which funds research in climate science. Evaluating loss and damage is the “big, big, big way forward” for attribution science, said Davide Faranda, a climate physicist at France’s National Center for Scientific Research, where he leads ClimaMeter, a project that produces rapid attribution analyses. He acknowledged the role of researchers is to provide evidence, not determine how it gets used. Even so, he can’t help but feel disheartened by what he sees as a lack of interest among elected officials in the findings of attribution science. “It should be the job of the politicians to use all this science that is out there,” Dr. Faranda said. “That’s where we are stuck.” Indeed it should, Dr. Faranda. Why it isn’t is a story that needs to be told.