February 1, 2014
Environmental hazard: Traffic slows to a halt during haze caused by air pollution in New Delhi in January.
Surging air pollution from China and other fast-growing Asian
economies has intensified winter cyclones in the Northwest Pacific,
scientists announced recently.
Winter cyclones in latitudes that include northwestern China, South
Korea and Japan have packed stronger winds and more rain as a result of
rising levels of particulate pollution, they said.
The dusty fallout affects how moisture develops in clouds and how
heat is distributed in storm systems, said Yuan Wang of the prestigious
Jet Propulsion Laboratory at the California Institute of Technology.
“The significant change of the Pacific storm intensity was estimated to start in the middle of the 1990s,” Wang said.
“(This was) when industrial plants, power plants and automobiles
produced huge amounts of air pollutants, along with the booming economy,
in many Asian countries such as China and India.”
The study, published in the journal Nature Communications, is the
latest probe into the environmental hazard from particulates, which are
mainly the sooty residue from burning fossil fuels.
Aerosols accelerate the formation of droplets because they provide a
nucleus on which water vapour condenses, according to Wang’s
Clouds influenced by aerosols carry as much as four times more
droplets, leading to a roughly 7 percent increase in rainfall across the
region, it found.
The aerosols are also likelier to encourage the formation of brighter high-altitude cirrus or “anvil” clouds.
These are a type of cloud that help to warm the sea surface, thus providing heat to fuel cyclones.
The additional warming effect can be as much as 11 percent.
The scientists drew up a computer model to simulate aerosol pollution
flowing downwind from East Asia to a cyclonic breeding ground east of
Japan in January and February, a zone lying north of 30 degrees
They found a good match with two decades of satellite data: 1979-88 —
before the Asian economic boom got underway — and 2002-11, when growth
really hit its stride, especially in China.
In the latter period, there was a clear rise in cyclone intensity but no change in frequency of storms or location, said Wang.
On Jan. 16, a study led by Ho Chang-hoi from Seoul National
University in South Korea found that China, Korea and Japan had been hit
by more powerful cyclones between 1977 and 2010, due to a warming of
water in the tropical western Pacific.
The two investigations are not comparable, Wang said.
The first looked at cyclones forming in wintertime in mid-latitude in
the northwest of the ocean, and the second examined cyclones in the
summer and autumn that form in tropical latitudes.
Research into the effect of aerosols on clouds has returned highly
variable findings — indeed, it is considered to be one of the biggest
areas of uncertainty in climate science.