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Worrisome Weather: Atmospheric blocking is becoming less rare, and climate scientists are concerned.

Climate scientists say “atmospheric blocking” events, periods of “stagnant” weather caused by an unusually long-lived area of stationary high pressure, may become more common as the planet warms. This is a cause for concern because, though relatively rare, blocking can have profound effects. The prolonged heat wave in 2003 that killed 40,000 Europeans is an extreme example.

Learning more about blocking events and their relationship to increased carbon dioxide in the atmosphere will help scientists like MU’s Tony Lupo to “better predict blocking and warn people in cases of long-lasting, severe weather.”

Lupo, professor and chair of the atmospheric science department at MU, says atmospheric blocking typically occurs between 20 and 40 times each year, usually lasting between 8 and 11 days. His current research project, Lupo says, aims to “see if increased carbon dioxide in the atmosphere and the resulting atmospheric warming will affect the onset and duration of future blocking events.”

The investigation will be conducted in collaboration with researchers from the Russian Academy of Sciences. The scientists will simulate atmospheric blocking using computer models that mirror real-world blocking events, then introduce various carbon dioxide environments into the mix. As carbon-enhanced atmospheric temperatures rise, the scientists will observe how the dynamics of atmospheric blocking events change in response.

Blocking usually results when a powerful high-pressure area gets stuck in one place. Because these high-pressure centers cover large areas, the movement of additional weather-producing fronts can get stuck behind them. Lupo believes that heat sources, such as radiation, condensation, and surface heating and cooling, will prove to have a significant role in a blocking’s onset and duration. Thus, he fears, planetary warming might increase the frequency of blocking events.

The good news, Lupo says, is that blocking events in a warmer world will probably be less intense than those we experience today. On the other hand, he says, they will probably be more numerous and longer-lived.

“This could result in an environment with more storms,” he says. “We also anticipate the variability of weather patterns will change dramatically over some parts of the world, such as North America, Europe and Asia, but not in others.”

The project is funded in part by the U.S. Civilian Research and Development Foundation, an Arlington, Va.-based nonprofit with offices in Moscow and Kiev. Lupo’s study is one of only 16 grants awarded by the group this year.

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