By Tom Spears

Canada's trees not so cool: scientist
CANADA'S forests may actually worsen global warming rather than cool the planet, says a controversial study by a Stanford University physicist and environmental scientist.
This doesn't mean we should bulldoze forests to fight global warming, says Ken Caldeira. Forests are still valuable ecological features in many ways.

But he says it's "premature at least," and maybe even dead wrong, to plant new forests and maintain existing ones in the belief that this will cool the Earth. If we want to stop global warming, he says, we'd better begin by burning less fossil fuel.
This is, he admits, an unpopular view with many.
Since he presented his paper at the conference of the American Geophysical Union last month, he's been getting an earful. "Somebody from the California Forest Service contacted me and said: 'What are you doing? We're trying to plant forests, and are you some kind of evil guy?' "
The finding also challenges Canada's official stance -- that we should get credit for maintaining huge forests when countries decide how much to should reduce their burning of coal, oil and gasoline under the Kyoto Protocol.
Here's how the Caldeira theory works:
First, it's true that growing trees soak up carbon dioxide from the air. This removes the main gas causing global warming, and locks it up in wood.
But he says tropical rainforests are the only ones that actually cool the Earth. They not only soak up carbon dioxide, but also give off great amounts of moisture, producing clouds which reflect sunlight back into space.
Meanwhile the temperate forests (those in most of the U.S. and southern Canada) and boreal ones (farther north) are problems, he claims.
Trees are designed to soak up massive amounts of energy from the sun. Much of this, he argues, is gradually released in the form of heat, especially in dark evergreen forests in the north, but also in temperate forests of maple, poplar and beech. Unlike tropical forests, Canadian forests don't release much cooling moisture.
His computer model indicates that this warming influence is more powerful than the cooling job that forests do when they soak up carbon dioxide -- especially since mature forests don't soak up all that much because they don't grow bigger forever.
In one simulation, the team covered much of the northern hemisphere with forests and saw a jump in surface air temperature of nearly three Celsius degrees. That said, Caldeira still wants forests protected for other reasons.
"I like forests. They provide good habitats for plants and animals," he said.
His five-member team published their results in the journal Geophysical Research Letters.
But a senior Canadian ecologist warns that forests and climate and terribly complex, and no computer model is likely to tell the full story.
David Schindler of the University of Alberta recalls years studying lakes in northwestern Ontario, including areas where forests had burned away
"Once the forests were gone, we had much, much hotter conditions just from the black rock underneath, and so on, absorbing sunlight instead of the trees," he said. "If the trees do transpire (give off moisture) it cools things down."