Page 11 - AsiaElec Week 02 2023

AsiaElec POLLUTION AsiaElec

Central Asian rain may be caused

by Indian, Chinese pollution

ASIA Despite a devastating drought in recent years, Ocean to Central Asia. The orange dots repre-
summers in Central Asia and Xinjiang are sent aerosol sulfates from man-made pollution.
trending wetter, featuring more heavy storms (Xie et al.)
and flash floods. New research points to a poten- Xie and his team also model the effect of a
tial cause thousands of miles away. hypothetical spike in black carbon soot, which
When factories, cars and power plants in the they find would push the Asian Westerly Jet
industrial regions of northern India and east- Stream in the opposite direction (to the north)
ern China burn fossil fuels, they release aerosol and reduce summer rains in Central Asia. Spikes
sulfates. These particles, such as sulfur dioxide, in the greenhouse gas carbon dioxide, they find,
reflect sunlight, cooling the atmosphere and increase rainfall in Central Asia only in spring
causing pressure changes that alter established and autumn.
air currents. The research was funded by both the Chinese
According to Xiaoning Xie of the Chinese and US governments.
Academy of Sciences and colleagues in a new The aerosol sulfates may even explain Cen-
paper in Nature: Communications Earth & tral Asia’s drought of 2021, the worst in decades.
Environment, this pollution is shifting the Asian COVID slowed economic activity around the
Westerly Jet Stream (see map) southward while world in 2020 and 2021, leading factories in
pulling moist air from the Indian Ocean into India and China to cut output. The drop in pol-
Central Asia. lution and rainfall is consistent with the authors’
The cause of Central Asia’s summer storms findings.
has been previously disputed, with other As Xie and his team have shown, human
researchers examining the effects of greenhouse activity in one region can impact areas far away.
gases or the region’s rapidly thawing glaciers. What the weather holds in store for Central
Xie and his colleagues focus instead on Asia may depend on China’s attempts to reduce
modelling the effect of hypothetical sulfate con- pollution on its eastern seaboard. “Regional
centrations on wind and cloud patterns, using emissions over Asia have been rapidly changing
an established method that accounts for solar since 2010,” the authors note, falling in eastern
radiation and the resulting cloud-to-rain conver- China and increasing in the subcontinent. “How
sions. Their simulations project dryer monsoons this change of aerosol emission distributions will
in the subcontinent and eastern China and a sig- affect [Central Asian] precipitation merits fur-
nificant increase both in summer precipitation ther investigation.” ™
and in the frequency of extreme precipitation
events in Central Asia. David Trilling is Eurasianet’s managing
The Asian Westerly Jet Stream (in yellow) is editor. This article originally appeared on
shifting southward while southwesterly winds Eurasianet.
(green arrow) carry moisture from the Indian

The Asian Westerly
Jet Stream (in yellow)
is shifting southward
while southwesterly
winds (green arrow)
carry moisture from the
Indian Ocean to Central
Asia. The orange dots
represent aerosol
sulfates from man-
made pollution.

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