How Climate Change Will Lead to More Deadly Stagnant-Air Days

Many regions, including the U.S, are expected to experience yet more frequent "still-air events" later this century.

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Air pollution shrouds the sky in New Delhi, India. (Altaf Qadri/Associated Press)

More terrible news for those looking forward to the weather of tomorrow: If greenhouse-gas emissions stick to their current levels, the world will not only be more ovenlike and full of fire but the air could be so stagnant and foul it'd be like living inside the cavity-ridden mouth of an unkempt dog.

Researchers at Stanford University have modeled the frequency of "still-air events" in the coming decades, and the results are anything but encouraging. The warming climate is predicted to shift historical patterns of precipitation and wind, creating many new regions where rain is scarce and there's not enough breeze at ground level to move a hair on a sweaty head. These doldrums-like conditions are the perfect recipe for air stagnation, an atmospheric condition that often allows pollutants to build up to levels that are harmful to the cardiovascular and respiratory systems.

Roughly 7 millions premature deaths—or one in eight deaths, globally—could be attributed to air pollution in 2012, according to the World Health Organization. The Stanford study, published in Nature Climate Change, suggests the lethal plague will only get worse. By later this century, nasty, sluggish air could frequently cover about 55 percent of the planet's population. And some places could see a leap of as many as 40 new stagnant-air days a year, the researchers say. They expect the problem to be at its worst in India and China, though the western United States, Mexico, and the Mediterranean are likely to experience it as well.

Here are two of their simulations they made showing where days of air stagnation are predicted to increase (shown in red) and decrease (blue) for early and late in the 21st century. The places expected to have an uptick in unmoving air outnumber those that aren't by 10 to one, according to their calculations, which were based partly on info from the National Climatic Data Center:

It's worth noting that several of the stagnation zones are already struggling with dire air pollution. There are China's major urban areas, so smoggy they can appear from space that they're on fire, and of course India, which is where the above photo was taken last February during a particulate-matter storm of 250 micrograms per cubic meter. That's more than 10 times the concentration considered safe by the WHO.

Should the atmosphere start propagating more and more of these areas of snail-paced air, it won't only be bad news for public health, but would be a headache for regulators as well. Explains the study's lead author, Daniel Horton:

"Since the 1960s, many nations have begun legislation-based initiatives to limit the amount of pollutants that can be emitted into the atmosphere. The U.S. policies have been effective at decreasing concentrations of the six most common pollutants by about 70 percent," Horton said. "Our new research suggests that global warming could impact some of that effectiveness by increasing the occurrence of stagnation. If so the pollutants that do exist could accumulate more frequently, increasing the risk of poor air quality."

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