Dear EarthTalk:

Have scientists been able to definitively prove links between global warming and more extreme weather phenomena in recent years, or is this still just a theory?

T.C., Chicago, IL

The question of whether science has been able to prove, let alone prove definitively, the connection between climate change and extreme weather is a very tricky one. This is because science is always reluctant to deal in certainty. “You can never have 100 percent proof of anything. There will always be doubt,” reports Jack Fraser, an Oxford-trained astrophysics Ph.D. at the Wellcome Sanger Institute. “Proof can only exist when there is no doubt, and there is always doubt. You could be a brain in a vat, living in a crazy simulation. You could be hallucinating everything. You cannot prove anything.” 

Despite this embedded doubt in all things scientific, researchers have opened up a new branch of science called ‘Extreme Event Attribution’ in an attempt to work out the extent of man-made climate change’s culpability. To discern this, scientists begin by setting criteria for what made the event extreme. They then turn to historical climate records and make comparisons with other similar events, checking them against the same criteria. They are looking for a change in the intensity or frequency of a certain extreme event. 

If they find a change, they then work out what caused it. To do this, they use models. There are many different types of models; one example is creating two virtual worlds with exactly the same conditions, except one is pumped full of greenhouse gasses. These simulations then create thousands of weather scenarios allowing a direct comparison between the polluted world and the non-polluted world. The difference between the two suggests man-made climate change’s culpability in certain weather events. 

Although new, this form of science has already gone as far as science permits into proving the role of climate change in certain extreme weather events. “The vast majority of extreme weather events reviewed by researchers since 2011 – 70 percent – were shown to be more likely to occur, or were made more severe, because of global warming,” Eric Roston and Brian Sullivan report in The Washington Post.

Take the floods in Pakistan in 2020, for instance. The World Weather Attribution scientists say that their “evidence suggests that climate change played an important role in the event, although our analysis doesn’t allow us to quantify how big the role was.” And Frederike Otto, a climatologist from Imperial College London, said that “the fingerprints of global warming [were] evident” in the disaster. 

Extreme Event Attribution is a particular science that works on a case-by-case basis, but the trend is clear. Seventy percent of extreme weather events were made more likely or more damaging by man-made issues. Definitive proof will never be offered by science, but most studies point in the same direction: towards global warming.  

CONTACTS

• NASA Vital Signs: Sea Level, climate.nasa.gov/vital-signs/sea-level/
• “There's No Such Thing As Proof In The Scientific World - There's Only Evidence,” forbes.com/sites/quora/2017/12/14/theres-no-such-thing-as-proof-in-the-scientific-world-theres-only-evidence/
• “How Science Links Global Warming To Extreme Weather,” washingtonpost.com/business/energy/how-science-links-global-warming-to-extreme-weather/2022/07/18/80b19e1a-06ca-11ed-80b6-43f2bfcc6662_story.html.