El Niño defeats rain forest benefit
In an El Niño year, Brazil's rain forest exhales millions of tons
carbon dioxide, potentially adding to global warming, scientists say.
Under normal conditions the rain forest acts as the ``lungs'' of the planet.
canopy of trees stretches for thousands of miles, releasing oxygen and absorbing
as much as 700 million tons of carbon dioxide a year.
But when global climate conditions are scrambled by El Niño and
the rain forest
becomes parched, the Amazon Basin produces as much as 200 million tons of
excess carbon dioxide a year, scientists from the Woods Hole Research
Laboratory in Massachusetts determined. The calculations were published in
Thursday's journal Nature.
The study examined three El Niño episodes from 1980 to 1994. It
did not include
measurements of the record-setting El Niño in 1997-98, but the trend is clear,
``In El Niño years, which bring hot and dry weather to much of the
ecosystems act as a source of carbon,'' said researcher Hanqin Tian.
Scientists say understanding the planet's fluctuating carbon cycle is a
key step in
accurately predicting -- and managing -- global warming in the 21st Century.
Many natural features on the planet act as ``carbon sinks'' to absorb excess
carbon and help to stabilize the planet's climate. The oceans and the rain forests
absorb the largest shares, along with tundra and rangeland.
But not always.
During an El Niño, a vast pool of warm water expands in the equatorial
upsets weather patterns around the world. In the Amazon, it triggers severe
Under such severe stress, the forest can't adequately photosynthesize and
carbon dioxide, Tian said.