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New global warming evidence presented
Scientists say their observations prove industry is to blame
David Perlman, Chronicle Science Editor
Saturday, February 19, 2005
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.
New global warming evidence presented
Scientists say their observations prove industry is to blame
David Perlman, Chronicle Science Editor
Saturday, February 19, 2005
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.
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