Despite little data, scientists link storms to warming

A.M. Costa Rica file photo
Hurricane Luis was a major 1995 Atlantic hurricane that reached Category 4 with winds of 135 mph

Costa Rica has received a $3 million grant to help it set up a carbon trading scheme to offset emissions of so-called greenhouse gases. So far officials say that the buying and selling of carbon credits will be voluntary.

The country also has a goal to be carbon neutral by 2021.

The reason for these projects is the belief that a warmer earth will be a more violent place with what are called extreme weather events. There also is the concern that low-lying areas of the country will be flooded.

Since the levels of the ocean have risen as much as 200 meters (about 650 feet) since the end of the last Ice Age, there is little doubt that the levels will continue to rise. The only questions are how high and when.

Extreme weather events are another story. Scientists are quick to blame storms, droughts, flooding and other natural disasters on a warmer planet. They reason that warmer air holds more water, perhaps as much as 4 percent more for every 1 degree F. increase in sea temperature, according to Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colorado.

But as every scientist knows, determining a cause is not always easy or possible. Researchers at Washington University in St. Louis. Missouri, sought to determine causation. “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,” says Jonathan Katz, professor of physics at the university.

That did not stop President Laura Chinchilla from blaming the industrialized world in 2011 for causing damaging storms. She and other Central American presidents said that the intensity of the prolonged rain suffered in Central America during October of that year constitutes a concrete manifestation of the adverse affects of climate change and the direct impact of this over the life and existence of the population of the countries.

Katz and a student analyzed 70 years of hourly precipitation data from 13 U.S. sites looking for quantitative evidence of increased storminess, said the university. They published the results in an academic paper Friday in Nature Climate Change.

They found a significant, steady increase in storminess on the Olympic Peninsula in Washington State, which suffers from more or less continuous drizzle, a calm climate that lets storm peaks emerge clearly, said the university in a summary.

“We didn’t want to know whether the rainfall had increased or decreased,” said Katz, “but rather whether it was concentrated in violent storm events.”

“We found a significant steady increase in stormy activity on the Olympic Peninsula,” Katz said. “We know that is real.”

“We found no evidence for an increase in storminess at the other 12 sites,” he said in a university release, “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.” He said the scope of the study would be expanded.

Such work is critical to Costa Rica as the nation again approaches the rainy season that runs to December.

Others have no doubt that warmer weather means more severe storms. The University of Illinois at Urbana-Champaign quoted Donald Wuebbles, a professor of atmospheric sciences there who gave a presentation last month.

“Human-driven climate change is, in fact, driving changes in severe weather, and that leads to a lot of potential impacts in both humans and wildlife that end up being costly in many different ways,” Wuebbles said in a university release.

As the global climate changes, normal weather patterns are altered. This is because the increasingly warmer atmosphere holds larger amounts of water vapor, which energizes storms, Wuebbles said.

“What we’ve seen in general is that the number of billion-dollar events has increased over the last three decades,” Wuebbles said. “It’s not just hurricanes, it’s really a number of different types of weather extremes that are increasing, and that’s what the worry is.”

Hurricane Sandy caused a lot of damage in the New Jersey-New York metro area in October. And many were quick to blame increasing temperatures. However, researchers have catalogued hurricanes and tropical storms in the New Jersey area since the 13th century. Still the storm had the lowest pressure ever recorded in the state.

Trenberth in Boulder gave a presentation about the same time that Ms. Chinchilla was blaming the industrialized world.

The sea surface temperatures near all the extreme flooding events of 2010 were at record levels, Trenberth said. That includes the Caribbean, Gulf of Mexico, North Atlantic and the Indian Ocean, he added in a university summary.

“All of the storms are being formed in an environment that is warmer and wetter than before,” said Trenberth. “The main thing that has happened with climate change is that you have changed the environment.”

Another way of looking at it is in terms of the odds of extreme weather events. Extreme weather is always possible, after all. But with warmer oceans, such events are easier to create, the National Center for Atmospheric Research, said.

“We’re loading the dice in favor of extreme weather events,” said Trenberth.

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