SCIENCE:

A 'bulge' in atmospheric pressure gives us a super-cold winter amid global warming

Updated at 11 a.m. EST to include comments from meteorologist Joe Bastardi.

Icicle-covered oranges in Florida. The United Kingdom swamped with its coldest December in more than a century. Travelers stranded in airports surrounded by snowy fortresses.

These have been some of the dominant images this winter, and now one forecaster says it's going to get colder. Yesterday, an AccuWeather meteorologist predicted that January could be the chilliest for the nation as a whole since the 1980s.

"More waves of Arctic air will invade the country, starting late this week and continuing through the next week and beyond," explained Joe Bastardi of Accuweather in a release. Rare snowfall is headed to Seattle, while the Texas citrus industry may have to prepare for cold-weather damage, according to his forecast.

So how does this fit with global warming models?

According to some climate scientists, the cold in places like Florida actually could be a sign of warming, rather than an argument against the phenomenon.

The ongoing disappearance of sea ice in the Arctic from elevated temperatures is a factor to changes in atmospheric pressure that control jet streams of air, explained James Overland, an oceanographer of the National Oceanic and Atmospheric Administration, or NOAA. That is because ice-less ocean is darker and, thus, absorbs more solar heat, which in turn spews warmer air than average back into the Arctic atmosphere.

That unusually warm air can contribute to a "bulge" effect to the atmospheric pressure controlling how cold air flows, according to Overland, who works at NOAA's Pacific Marine Environmental Laboratory. Rather than moving circularly in the Arctic from west to east as typical, the bulge may prompt air to move in a U-shaped pattern down to the southern United States.

How loss of Arctic ice gives you snow in Seattle

Last year was the waviest example of this pressure phenomenon in 145 years, said Overland. What also is happening is that the wavy air flow from north to south is appearing for longer periods of time, rather than just for a week or two, he said.

"You can't go as far as saying the loss of sea ice is causing cold weather in Florida," said Overland. "You can say it is a contributing factor." In October, Overland co-authored part of NOAA's Arctic Report Card, which included a section on how Arctic weather is influencing weather in mid-latitudes.

He emphasized that more research needs to be done on the cause and effect relationship between disappearing Arctic sea ice and cold weather in southern locations. Other research backs up his argument.

In November, climate scientist Vladimir Petoukhov reported in the Journal of Geophysical Research that the overall warming of Earth's northern half could result in cold winters. "These anomalies could triple the probability of cold winter extremes in Europe and northern Asia," he said in a statement.

The area covered by sea ice hovered near its historic low this summer, and is expected to be largely gone by mid-century (ClimateWire, Dec. 17, 2010).

Another study published in Environmental Research Letters last year, though, predicted colder winters in the United Kingdom because of natural variations in solar activity.

Differing from the majority of scientists, meteorologist Bastardi presented his "global cooling" theory in a December AccuWeather video arguing that carbon dioxide is a trace gas that has less effect on weather than forces such as the sun.

"There's no need to panic over global warming," he said.

The key thing is to look at the climate over long periods of time and not try to find meaning in one weather event, said David Easterling, chief of the Scientific Services Division at NOAA's National Climatic Data Center.

"The flip side is it's been unusually warm in Canada this winter," he said.

January aside, the National Weather Service predicts that swaths of the country stretching from the Southwest to the Southeast will be warmer than average this year. Record high temperatures are currently outnumbering record low temperatures by about two to one, and those ratios are projected to be about 20 to 1 by mid-century and 50 to 1 by 2100, said Jerry Meehl, a scientist at the National Center for Atmospheric Research.

How much the existing data registers with politicians and the public is an open question.

Sen. James Inhofe (R-Okla.), who once called global warming a "hoax" and was one of the loudest opponents against climate legislation last year, posted a blog last month mentioning recent cold weather events.

How weather impacts belief

"The fanciful claims surrounding global warming have turned out to be a colossal deception, an artful hoax, and an intellectual fraud," it said.

According to the Center for Science and Technology Policy Research, news coverage of climate change in 50 newspapers around the globe dropped by more than half in late 2009 to 2010. That parallels the time frame that climate change fell off the radar of Capitol Hill and international climate negotiations ended in Copenhagen, Denmark.

Last year also witnessed a drop in public belief in man-made warming. Gallup, for example, reported that the percentage of the population saying that seriousness of warming is "exaggerated" jumped 15 points between 2007 and 2010.

Christopher Borick, director of the Muhlenberg College Institute of Public Opinion has studied public reaction to the climate change issue since 2008. He and his team found that an individual's belief or skepticism of its existence lies in personal experience: Unusually hot summers resulted in an increase in the number of believers, while frigid winters led to a greater number of skeptics.

"[Weather] has a big effect on the perception that climate change is happening," said Borick. "Meteorological phenomena, storms and droughts, can be translated by individuals to their views on what's happening with long-term climate."

In a survey last spring, following an unusually cold winter for many parts of the United States, the percentage of climate change believers stood at 52 percent, with 36 percent non-believers and 13 percent unsure. The number of believers rose 8 percent and the number of non-believers dropped 9 percent in the fall survey, taken just a few months after a hot summer.

But Jon Krosnick, a professor at Stanford University, said the only group affected by cold weather in terms of belief about climate change is the 30 percent of the population who distrust scientists. And then they only consider how the most recent season compares to the previous three years in terms of worldwide temperatures, he said.

If this winter is unusually cold, he said, you would expect to see a "small drop" in the percentage of people who think global warming is happening.

"People don't use their local temperatures as a benchmark," he said. "They are not dodos."

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