Global Warming Weakens Vast Pacific Climate System

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Global Warming Weakens Vast Pacific Climate System

 

May 04, 2006 — By Deborah Zabarenko, Reuters

WASHINGTON — Climate scientists identified a likely new victim of global

warming Wednesday: the vast looping system of air currents that fuels Pacific

trade winds and climate from South America to Indonesia.

 

This could mean more El Nino-like weather patterns in the United States, more

rain in the western Pacific and less nourishment for marine life along the

Equator and off the South American coast.

 

Known as the Walker Circulation, this system of currents functions as a huge

belt stretching across the tropical Pacific, with dry air moving eastward at

high altitude from Asia to South America and moist air flowing westward along

the ocean's surface, pushing the prevailing trade winds.

 

When the moist air gets to Asia, it triggers massive rains in Indonesia. Then it

dries out, rises and starts the cycle again, heading east.

 

This important system has weakened by 3.5 percent over the last 140 years, and

the culprit is probably human-induced global warming, scientists reported in the

current edition of the journal Nature.

 

" This is the impact of humans through burning coal, burning benzene, gasoline,

everything, " said Gabriel Vecchi of the U.S. National Oceanic and Atmospheric

Administration and an author of the study. " It's principally the greenhouse

gases from fossil-fuel burning. "

 

The observed slowdown has been more pronounced in the last 50 years, Vecchi said

in a telephone interview, noting this fits with what theorists and computer

models predict should happen as a result of human-induced global warming.

 

It is not consistent with any natural fluctuation in the system, Vecchi said.

 

Even this relatively small weakening in the Walker Circulation means a much

larger slowing of wind-forced ocean currents, the scientists found. This could

spur " El Nino-like " effects, Vecchi said, and these in turn could have an impact

as far as the United States, South America and Australia.

 

While these potential effects are being studied, Vecchi said it could mean more

rain in the southern United States, droughts elsewhere in North America, and

more rain in Pacific islands like Kiribati.

 

The slowdown in ocean currents is also expected to cut down on bottom-to-top

ocean circulation that brings nutrients up to the surface where marine life can

feed on them, which could have an impact on fishing in the equatorial Pacific.

 

The weakening of the Walker Circulation is projected to continue, and could

weaken another 10 percent by 2100, the scientists reported. This could mean

ocean flow could decrease by close to 20 percent.

 

Source: Reuters