March 18, 2013
Stormier Weather In The Northwest Due To Manmade Climate Change
Lawrence LeBlond for redOrbit.com - Your Universe Online
The evidence for manmade climate change is pretty strong. And most scientists hold little doubt that massive amounts of greenhouse gases released into the atmosphere have caused warmer climes since the onset of the Industrial Revolution. However, when it comes to stormy weather, the evidence has been limited.One scientist, Jonathan Katz, PhD, professor of physics at Washington University in St. Louis (WUSTL), looked at the quantitative evidence of more than 70 years of rain data across 13 US sites to paint a clearer picture of increased storminess.
“Although many people have speculated that the weather will get stormier as the climate warms, nobody has done the quantitative analysis needed to show this is indeed happening,” said Katz in a statement.
Katz, along with Thomas Muschinski, a senior in physics at WUSTL, reported the results of their analysis in the March 17 online issue of Nature Climate Change. They used data gleaned from the National Oceanic and Atmospheric Administration (NOAA), which has hourly precipitation data since 1940 and even further back in localized areas.
Katz and Muschinski chose the 13 sites that had the longest runs of data and represented a wide range of climates, from arid desert to rainforest. They then tested the theory that storms had become more frequent and intense in these locations by taking different measurements of the “shape” formed by the data points for each of the 13 sites.
The measurements Katz and Muschinski utilized were statistical tests commonly used in science, but had not been applied to this area before. Using these “moments,” as they are called, the researchers found in one particular region, the Olympic Peninsula in Washington State, a significant and steady increase in storminess has occurred since the 1940s.
Katz noted that detecting stormier weather in the Olympic Peninsula, which more or less suffers from a continuous drizzle, was easier than in other areas because storms tend to stand out more clearly from the calmer rains typically seen.
"Other sites have always been stormy," Katz says, "so an increase such as we saw in the Olympic Peninsula data would not have been detectable in their data."
Katz noted that for the study they were not looking to see “whether the rainfall increased or decreased, but rather whether it was concentrated in violent storm events.”
Most previous studies have looked at precipitation amount or number of days in which precipitation occurred, but not whether conditions were becoming stormier, he said. By relying on the NOAA dataset, Katz explained that they were able to get the statistical power to pick up stormier conditions rather than actual rainfall amounts.
In all 13 sites they looked at, only the Olympic Peninsula showed increased storminess based on the data.
"We found no evidence for an increase in storminess at the other 12 sites," he said, "but because their weather is intrinsically stormier, it would be more difficult to detect a trend like that at the Olympic Peninsula even if it were occurring."
Katz said more research is needed to see if other areas are experiencing an increase in storminess. He plans to look at more data of a much larger number of sites that might be regionally averaged to reveal trends too slow to be significant for one site.
"There are larger databases, but they're also harder to sift through. Any one site might have half a million hourly measurements over the period we're looking at, and to get good results. we [sic] have to devise an algorithm tuned to the database to filter out spurious or corrupted data," Katz concluded.