Growing Deserts, Growing Dust Storms
Carbon dioxide emitted in China raises carbon dioxide levels everywhere. Dust and particulate pollution tends to have its greatest impacts locally, but it can cast a wide net too.
New research on a massive 2007 dust storm that began in the Taklimakan desert of Xinjiang, reveals a cloud of dust that took an unusual flight around the globe, passing over the United States, Europe and Asia before returning to the Pacific Ocean, where it deposited some of its dust and minerals into the sea. Like the Atmospheric Brown Cloud, such massive dust clouds don't just travel the Earth, spilling their pollution on distant ecosystems. They also serve to dim the sun, hurt road visibility, and abet and conceal the effects of climate change.
How the Cloud Started, and Where It's Going
Unfortunately, China's dust clouds appear to be growing bigger due to desertification -- a fact that goes unmentioned in reports on the Japanese cloud study.
As Matt noted last year, China, which is roughly the same size as the United States, is almost one-quarter desert, and the desert is advancing at more than 1,300 square miles. That's approximately the size of the state of Rhode Island, each year.
Despite attempts to stem the spread of sand with programs seeking to lower the impact of cashmere farming, or build great green walls, the desert continues to spread thanks to unsustainable farming practices and the effects of climate change.
The Study's Findings
In a paper published in Nature Geoscience, scientists described how they used a NASA satellite and mathematical modeling to track and measure the movement of the dust cloud, which formed after the dust storm on May 8-9 in 2007.
The researchers, led by Uno, found that the dust clouds were lifted 8-10 km (5-6 miles) above the earth's surface, and transported more than one full circle around the earth.
"The most important achievement is that we tracked this through one full circuit round the globe, nobody has done this before. After half a circuit, usually the dust concentration gets very low and you can't track it," Uno told Reuters.
"This means that dust concentration, dust lifetime is very long, more than two weeks."
To put their observation in perspective, a 2003 Columbia University study that examined a dust cloud from the Taklimakan desert in 1990 found that the dust mostly traveled (only) as far as France, ending its journey after two weeks.
How It Traveled
The 2007 dust cloud, which weighed about 800,000 tons (wow) measured about 3 km vertically and up to 2,000 miles horizontally, maintained its shape and scale even after one full trip around the globe -- over the Pacific, North America, the Atlantic, Europe and Asia.
That's because the cloud rode the Tibetan plateau upwards to 5,000 meters, where a warm convection flow then carried the dust to a jetstream that took it on a fairly stable round-the-world atmospheric journey, between 8,000 and 10,000 meters high.
On its second trip around the globe, researchers say that some of the dust landed on the northwest Pacific due to an abrupt change in a high-pressure weather system, while yet more may have fallen in the Mid-Atlantic and Balkans.
Photo of a Taklimakan desert dust cloud from the NASA Aqua satellite
Silver Lining to the Brown Cloud?
The purpose of the study, was to examine the importance of airborne dust particles in forming high altitude cirrus clouds and reflecting sunlight, thus potentially easing global warming.
The UN doesn't call it "easing" global warming: it's more like a giant shield, masking the effects of global warming.
"One of the impacts of this atmospheric brown cloud has been to mask the true nature of global warming on our planet," United Nations Environment Program head Achim Steiner said last year, after a report on the larger, scarier Atmospheric Brown Cloud.
In certain locations, however, an increase of dust or soot from factories or forest fires can blanket ice and snow with a heat-absorbent black layer, accelerating a thaw.
Still, posit the researchers, the mineral-rich dust from the Taklimakan may also be nourishing the waters of the North Pacific, depositing iron that feeds phytoplankton, the microscopic marine plants that are the first link in the oceanic food chain.
Much more study remains to be done, both on the formation and lifespan of such clouds, and on their connections to climate change.
The next Intergovernmental Panel on Climate Change report will look closer at clouds and the effects of dust and aerosols on the climate.
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