After a summer of high profile extreme weather events across the US, and the world, weather experts have been hearing one question more than any other – “Is this weather, or climate change?”
When I interviewed TV weathercasters in June, I asked the question myself. Here, TV Met Dan Satterfield answers, with help from leading Atmospheric and ocean scientists.
..heavy downpours along the Gulf Coast of the United States have increased since the middle of the last century. That trend is consistent with what climate experts have predicted would happen as greenhouse gases warmed the planet: more water vapor in the air to fuel extremely heavy rain.
By itself, that general connection isn’t conclusive evidence that global warming had a hand in the mid-August downpour in Louisiana. Now, however, a preliminary analysis of the event led by climate scientists at NOAA’s Geophysical Fluid Dynamics Laboratory found that warming due to greenhouse gases has made—conservatively—events like the one in August at least 40% more likely and 10% more intense.
Because the devastating flooding occurred due to the rainfall over the entire region, the scientists drew a geographical box around the part of the Gulf Coast impacted by the event, and studied the three-day rainfall totals in the region for the period from August 12-14. Over this region, observations indicate that rainfall amounts observed during the event usually happen somewhere in the region about once every 30 years. At any local site, the extreme rainfall totals were closer to 1-in-500 year events.
Climate scientists have long said that a warming atmosphere and oceans should lead to more intense and frequent rainstorms, because there will be greater evaporation, and warmer air holds more moisture. But until recent years most scientists have said it was not possible to link any single event to climate change.
Climate scientists have long said that a warming atmosphere and oceans should lead to more intense and frequent rainstorms, because there will be greater evaporation, and warmer air holds more moisture. But until recent years most scientists have said it was not possible to link any single event to climate change.
That is changing with the development of attribution studies, which use statistical analysis and climate modeling to compare the likelihood of an event occurring before industrialization, when there were essentially no greenhouse-gas emissions, and now, when the world is putting tens of billions of tons of carbon dioxide into the air each year.
Normally such studies can take months, largely because of the computer time required to run climate simulations. But the Louisiana study is the latest “rapid-response” research intended to determine the effect, if any, of climate change as close to the event as possible, to help inform policy makers and the public.
To speed the research, World Weather Attribution, the loose-knit research team that conducted this study, used models that have already been run. They were developed by NOAA scientists at the Geophysical Fluid Dynamics Laboratory in Princeton, N.J., and are sophisticated enough to capture the many different elements that contribute to weather in the Gulf Coast region, said Karin van der Wiel, a research associate at the laboratory.
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