Scientists affirm climate crisis fuels extreme weather

(Bloomberg) --Human-induced changes to the global climate have "a direct and well-understood impact" on extreme heat and rainfall, according to a landmark new US National Academies report. 

The assessment comes as weather disasters dominate the headlines and as the public and private sectors pour resources into trying to understand what's coming next. This week alone, the eastern US grappled with intense heat and wildfire smoke; forecasters warned of dangerous flooding in Texas; and fire risk in Northern California prompted power shutoffs. The report is a step up in seriousness and authority — and potentially influence — for attribution science, a field that's blossomed in plain view and relatively quickly.

"Attribution science is being increasingly used for planning and risk management by both governments and businesses to really understand the changing risks that climate change poses," said James Hurrell, a climate scientist at Colorado State University and chair of the NAS author panel.

Attribution in recent months has entered the political arena, as the scientific research matures into a body of work potentially applicable to tort law or regulation. Attribution research emerged in tandem with the idea — following anti-tobacco and anti-asbestos movements — that the fossil-fuel industry could potentially be held legally accountable for selling products with byproducts known to heat the planet. Cities and states have filed many lawsuits against oil majors in recent years, with many complaints dismissed, lost or eternally in process.

"All of this has attracted tremendous interest because — and I speak as a former judge and a former prosecutor — this type of evidence could be very powerful in terms of any kind of liability lawsuit," said Alice Hill, a climate risk expert at the Council on Foreign Relations who was not a part of the NAS report. She previously served as a California judge and US prosecutor.

Extreme event attribution has in 10 years gone from novel research to a maturing topic of interest to the public, investors, emergency managers and many companies. The world could spend $20 trillion in the next decade on costs related to extreme weather, according to a Bloomberg Intelligence estimate. The figure for 2025 was $1.4 trillion. 

In the 10 years since the first major National Academies team looked at the topic, climate attribution research leaped from research journals to worldwide headlines, as groups like World Weather Attribution and ClimaMeter began to regularly release analyses of wild weather episodes just after they occur. WWA was able to run its standard analysis on last month's European heat wave before it was over.

Extreme weather comes in many types, and some of them are easier than others to analyze for climate influence. Heat waves are all more intense than they would have been, simply because the world is 1.3 degrees Celsius hotter than before industrialization, experts commonly point out. Attributing heat waves has become so straightforward that the research nonprofit Climate Central maps automated estimates of how much more frequent temperatures are — or infrequent for cold weather. Tornadoes, hail and thunderstorms remain too small for models to resolve reliably and still challenge attribution researchers. 

In the last few years researchers have begun to estimate the effects of greenhouse gas pollution not on weather alone but the harms and damage it can bring. That might mean deaths from heat or flooding or economic losses from crop failures. This "extreme event impact attribution" work is significantly more complicated than conducting weather-and-climate analysis alone. It must incorporate not only the physical hazards — such as heat, rain, drought or fire — but also the exposure of the built environment and the vulnerability of communities to withstand hardship.

And that takes a large team of people with diverse expertise, beyond climate science, to public health, economics and engineering.

"It's very complicated because it depends on much more than on attributing the physical event itself," Hurrell said.