Scientists: Earth will lose global protection
- Scientists: Earth will lose global protection
Computer model shows planets ability to fend off global warming
By Ian Hoffman, STAFF WRITER
Inside Bay Area
Scientists speeding through decades by supercomputer are concluding
that the Earths built-in resilience to global warming the great
carbon storage capacity of its oceans and forests could be coming
to an end.
Climate researchers know the worlds plants, soils and seas recently
have been absorbing billions of tons more carbon dioxide than in the
past 400,000 years. This breathing biosphere in essence has kept more
than 60 percent of human fossil-fuel emissions from trapping solar
energy in the atmosphere and warming the planet.
But scientists have disagreed on how much more carbon these natural
repositories can take.
In experiments and satellite images, increasing carbon dioxide
appears to be fertilizing plants in North America, making them lush
and greener in the springtime. But can humans continue relying on
plants, bacteria and other species of land and sea to cushion the
effects of increasing fossil-fuel burning?
According to the most recent supercomputer simulations, the answer is
Inez Fung, head of the University of Californias Berkeley Atmospheric
Sciences Center, led a team peering 100 years into the future as
humans continue expanding reliance on fossil fuels for energy. What
they found was a slow loss of the biospheres resilience to carbon
dioxide and accelerated globalwarming.
The computer simulation that they used was unrealistic in some ways:
Plants were allowed unlimited nutrients. Redwoods could grow as tall
as they wanted, without regard for getting water to the crown.
"There's a maximum capacity of the land. Here we're just ignoring
that," Fung said.
Even then, the plants ran into metabolic limits. And as summer heat
and droughts increased, the plants cut back on their intake of carbon
dioxide in order to save water, then turned brown and stopped
breathing carbon dioxide altogether.
Likewise, the upper layer of the ocean becomes warm enough that
carbon dioxide at the surface no longer is churned down to great
depths impeding the absorption of more carbon dioxide.
"With the ocean, think of it as a leaky pipe," Fung said. "If you
stuff things down faster, that leakage rate is going to slow down."
By 2050, global temperature had risen 2.5 degrees, which ranks low
among projections of global warming over the same period. A less
conservative simulation, for example one with limited nitrogen or
other nutrients in soils or more realistic tree growth, would remove
less carbon dioxide from the air and return it more quickly as the
Stanford scientist Ken Caldeira ran a climate simulation 200 years
into the future while working at Lawrence Livermore National
Laboratory and found a point late in the 21st century when the
biosphere caved, clouds vanished and the temperature started soaring.
The study by Fung's team suggests that leveling carbon dioxide
emissions off now or at least within 30 years could preserve the
"There is a window of opportunity," she said.
Contact Ian Hoffman at ihoffman@...