Good clouds, bad clouds.

Asian dust cloudsOk, so it’s hard to think of massive clouds of dust and pollution traveling at high speeds across the ocean as a good thing, but a team of scientists from both sides of the Pacific is trying to get a handle on how these phenomena effect weather and global warming.

The goal is to help provide a reality check on climate models, which poorly represent the effect these particles have on the global and regional climate…

By any measure, the Asian plumes represent some of the largest pollution events on Earth, researchers say. While air pollution also migrates from North America to Europe, and from Europe across Eurasia, those amounts pale in comparison to Asia’s eastbound freight.

Soot from Asia that reaches the West Coast accounts for 80 percent of the black-carbon soot in the skies over the United States, notes Veerabhadran Ramanathan, director of the Center for Clouds, Chemistry, and Climate at the Scripps Institution of Oceanography in La Jolla, Calif. More generally, natural and man-made particles in the plumes represent the single most vexing problem atmospheric scientists face as they strive to understand the handful of outside factors, or “forcings,” that affect Earth’s climate system.

Scientists have known for some time now that aersols–tiny particulates of matter released into the atmosphere from coal plants, diesel engines, wood burning, airplanes, you name it–actually help mask or minimize the effects of global warming by reflecting sunlight back out of the atmosphere. Exactly how much and for how long has been far more difficult to answer, but some surprising events have taught us a lot about these gorillas (or should we call them godzillas?).

For three days immediately after 9/11, the Federal Aviation Administration shut down all commercial flights in the United States, giving climate scientists a unprecedented opportunity to see how much the contrails from jet airplanes effected temperatures. They documented a temperature increase of 3.2 degrees Fahrenheit, the “biggest diurnal temperature range of any three-day period in the past 30 years.”

So, while we know that air travel is a rapidly growing source of greenhouse gas emissions–one for which no alternatives currently exist–things could be worse if we immediately stopped flying? Now, what about these dust clouds produced from Asian industry and energy production?

Over the Pacific on a clear day, the plumes can cut sunlight reaching the ocean surface by 10 to 15 percent, scientists say. Globally they may be concealing as much as half the warming effect of the carbon dioxide that human industrial processes have pumped into the air since the beginning of the Industrial Revolution, researchers add.

Gulp, did I read that right? And when you factor in the possibility that these pollution clouds may also reduce the number of hurricanes and typhoons, does that mean it’s a good thing that Asian factories are pumping out all this nasty stuff? Not so fast.

Ramanathan, who took part in a similar, larger-scale experiment over the Indian Ocean in 1999, notes that this time black-carbon soot is appearing at far higher altitudes than it did over the Indian Ocean.

“That worries me greatly,” he says, because the higher the soot, the longer it remains in the atmosphere. Soot at six miles up has two to three times the warming effect of soot at half a mile up, he says, because of its persistence at higher altitudes.

Moreover, high in the troposphere, winds can carry aerosols and soot around the globe in under two weeks, affecting cloud formation far from the aerosols’ sources. In addition, wispy cirrus clouds form at those altitudes from ice crystals and can amplify the greenhouse effect.

And, of course, none of this gets at the health effects of particulate matter in the air.

WHO estimates that 1.5 billion urban dwellers face levels of outdoor air pollution that are above the maximum recommended limits. In Asia – with half of the world’s city dwellers – more than 500,000 people die every year from diseases related to air pollution. About half a million deaths each year globally can be attributed to particulate matter and sulphur dioxide in outdoor air. Bringing suspended particulate matter down to safe levels could save between 300,000 and 700,000 lives annually, said WHO.

Not to sound trite, but this stuff is confusing. It’s clear that climate change is incredibly complex and can’t be isolated from other immensely complex issues–economics, poverty, health–which means that measures we take to mitigate global warming can have disastrous short-term or long-term impacts. Is that an excuse for further inaction? No. But it does make me respect even more Larry Brilliant &‘s focus on global poverty, climate change and global public health. I hope that they can muster the resources and ingenuity to develop solutions that address the nexus of these three issues.


One thought on “Good clouds, bad clouds.

  1. Pingback: Battlefront Coal. « Climate Changers

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