“Climate-driven changes are already evident over the last few decades for severe thunderstorms, for heavy precipitation and flash flooding, for hurricane activity, and for heatwave, drought and wild-fire dynamics in parts of North America.”
So concludes Munich Re, a top reinsurer, in a major new study that, for the first time, links the rapid rise in North American extreme weather catastrophes to manmade climate change.
Prof. Peter Höppe, who heads Munich Re’s Geo Risks Research unit, said:
“In all likelihood, we have to regard this finding as an initial climate-change footprint in our US loss data from the last four decades. Previously, there had not been such a strong chain of evidence. If the first effects of climate change are already perceptible, all alerts and measures against it have become even more pressing.”
The 274-page study, “Severe weather in North America” draws on “the most comprehensive natural catastrophe database worldwide,” though my favorite part is four words at the bottom of the back jacket:
This study builds on a September 2010 analysis by Munich Re, “Large number of weather extremes as strong indication of climate change,” which concluded:
… it would seem that the only plausible explanation for the rise in weather-related catastrophes is climate change. The view that weather extremes are more frequent and intense due to global warming coincides with the current state of scientific knowledge
At the time Höppe, explained to me what had persuaded him of the causal link:
For me the most convincing piece of evidence that global warming has been contributing already to more and more intense weather related natural catastrophes is the fact that while we find a steep increase in the number of loss relevant weather events (about tripling in the last 30 years) we only find a slight increase in geophysical (earthquake, volcano, tsunami) events, which should not be affected by global warming. If the whole trend we find in weather related disaster should be caused by reporting bias, or socio-demographic or economic developments we would expect to find it similarly for the geophysical events.
And that was before two years of off-the-charts extreme weather catastrophes, particularly in North America (see NOAA Chief 11/11: U.S. Record of a Dozen Billion-Dollar Weather Disasters in One Year Is “a Harbinger of Things to Come”).
It was also before multiple studies linking the surge in extreme weather to global warming, particularly in North America (see NOAA Bombshell: Warming-Driven Arctic Ice Loss Is Boosting Chance of Extreme U.S. Weather and links therein and below).
The new study finds:
Nowhere in the world is the rising number of natural catastrophes more evident than in North America. The study shows a nearly quintupled number of weather-related loss events in North America for the past three decades, compared with an increase factor of 4 in Asia, 2.5 in Africa, 2 in Europe and 1.5 in South America.
The study draws on a forthcoming journal article on how global warming is driving up “large-scale thunderstorm forcing”:
The results of the study indicate that climatic changes have driven up multiyear averages of thunderstorm-related normalized losses since 1970 and that anthropogenic climate change, most likely responsible for increasing levels of humidity over time, is fully consistent with this change.
Here’s a key figure on thunderstorm losses from the Munich Re study, “normalized to the current amount of destructible wealth exposed in the areas hit.” The “normalized annual overall thunderstorm losses displays a clear positive trend, even if the recordbreaking year 2011 is ignored“: