[Mabeavyledlib]

New global warming evidence

presented; Scientists say their observations prove industry is to blame
David Perlman /

San Francisco

Chronicle

Washington -- Scientists reported Friday they have detected the clearest evidence yet

that global warming is real -- and that human industrial activity is largely responsible for it.

Researchers at

the annual meeting of the American Association for the Advancement of Science cited a range of evidence that the

Earth's temperatures are rising:

-- The Arctic regions are losing ice cover.

-- The populations of whales

and walrus that Alaskan Eskimo communities depend on for food are crashing.

-- Fresh water draining from ice

and snow on land is decreasing the salinity of far northern oceans.

-- Many species of plankton -- the

microscopic plants that form the crucial base of the entire marine food web -- are moving north to escape the

warming water on the ocean surface off Greenland and Alaska.

Ice ages come and go over millennia, and for the

past 8,000 years, the gradual end of the last ice age has seen a natural increase in worldwide temperatures, all

scientists agree. Skeptics have expressed doubt that industrial activity is to blame for world's rapidly rising

temperatures.

But records show that for the past 50 years or so, the warming trend has sped up -- due,

researchers said, to the atmospheric burden of greenhouse gases produced by everything industrial, from power plants

burning fossil fuels to gas-guzzling cars -- and the effects are clear.

"We were stunned by the similarities

between the observations that have been recorded at sea worldwide and the models that climatologists made," said Tim

Barnett of the University of California's Scripps Institution of Oceanography. "The debate is over, at least for

rational people. And for those who insist that the uncertainties remain too great, their argument is no longer

tenable. We've nailed it."

Barnett and other experts marshaled their evidence and presented it to their

colleagues for the first time at a symposium here.

For the past 40 years, Barnett said, observations by

seaborne instruments have shown that the increased warming has penetrated the oceans of the world - - observations,

he said, that have proved identical to computer predictions whose accuracy has been challenged by global-warming

skeptics.

The most recent temperature observations, he said, fit those models with extraordinary accuracy.



But a spokesman for the Bush administration -- which has been criticized for not taking global warming seriously

-- was unfazed by the latest news.

"Our position has been the same for a long time," said Bill Holbrook,

spokesman for the White House Council on Environmental Quality. "The science of global climate change is uncertain."



"Ice is in decline everywhere on the planet, and especially in the Arctic, " said Ruth Curry, a physical

oceanographer at the Woods Hole Oceanographic Institution, "and there is large-scale drying throughout the Northern

Hemisphere."

Ice cores drilled deep into the Greenland ice cap show that salinity of the ice at the upper

layers of the cores has decreased sharply due to the incursion of fresh water draining from melting snows on the

surface, she reported, and land ice and permafrost are in decline all around the Arctic. In the meantime, she said,

measurements show that salinity of the ocean waters nearer the equator has increased as the rate of evaporation of

warmer tropical and subtropical oceans quickens.

It may take several centuries for all the ice that covers

Greenland to melt, Curry said, "but its release of fresh water will make sea-level rise a very significant issue in

this century." In fact, she said, changes in the freshwater balance of the oceans has already caused severe drought

conditions in America's Western states and many parts of China and other Asian countries.

Already, the physics

of increased warming and the changes in ocean circulation that result are strongly affecting the entire ecology of

the Arctic regions, according to Sharon L. Smith, an oceanographer and marine biologist at the University of Miami.



Last summer, on an expedition ranging from Alaska's Aleutian islands to the Arctic Ocean above the state's

oil-rich North Slope, Smith said she encountered the leading elder of an Eskimo community on Little Diomede island

who told her that ice conditions offshore were changing rapidly year by year; that the ice was breaking up and

retreating earlier and earlier; and that in the previous year the men of his community were able to kill only 10

walrus for their crucial food supplies, compared to past harvests of 200 or more.

Populations of bowhead

whales, which the Eskimo people of Barrow on the North Slope are permitted to hunt, are declining too, Smith said.

The organisms essential to the diet of Eider ducks living on St. Lawrence Island have been in rapid decline, while

both the plants and ducks have moved 100 miles north to colder climates -- a migration, she said, that obviously was

induced by the warming of the waters off the island.

Another piece of evidence Smith cited for the ecological

impact of warming in the Arctic emerged in the Bering Sea, where there was a huge die- off in 1997 of a single

species of seabirds called short-tailed shearwaters.

Hundreds of thousands of birds died, she said, and the

common plankton plants on which they depend totally for food was replaced by inedible plants covered with calcite

mineral plates. Those plants thrive in warmer waters and require higher-than-normal levels of carbon dioxide -- the

major greenhouse gas -- to reproduce, Smith said. "What more convincing evidence do we need that warming is real?"

Smith asked.