Scientists on AAAS Panel Warn That Ocean Warming Is Having Dramatic Impact
Tim Barnett, Ricardo Letelier, Sharon Smith, Ruth Curry
Photo credit: Edward W. Lempinen
Strong new evidence shows that ocean temperatures are rising because of human
activity, and the impact on people and ecosystems worldwide could be severe,
scientists on a AAAS panel warned Thursday.
Appearing on a panel at the 2005 AAAS Annual Meeting n Washington, D.C., the
scientists warned that global warming is already having an impact on plant and
animal species, with one citing a massive die-off of ocean birds in the Bering
Sea during the late 1990s.
The evidence-based on computer models and observations in the field-is so
strong that it should put to an end any debate about whether human-caused global
warming is a real phenomenon, said Tim Barnett, a research marine physicist in
the Climate Research Division at Scripps Institution of Oceanography at the
University of California-San Diego.
"The temperature-driven impact that these models predict over the next 30-40
years is severe, not only for the Western United States, but for China and
Peru," Barnett said.
"Other parts of the world will face similar problems," he added in an
unpublished paper released to reporters. The climate models "suggest that these
scenarios have a high enough probability of actually happening that they need to
be taken seriously by decision makers...if it is not already too late."
Scientists are already seeing that over the past decade, the ice mass of
Greenland has begun to decline, said Ruth Curry, a research specialist at the
Woods Hole Oceanographic Institution. Fresh water is accumulating in the nearby
ocean, and the ocean water is becoming less dense.
If the trend continues, Curry said, it could have a "radical" impact on ocean
ecosystems. Further, it could lead to a slowing or stalling of the water-flow
patterns in the Atlantic that pump warm water from the tropics toward the north
Atlantic and carry cold water south. That, she said, could lead to dramatically
colder winters ranging from Scandinavia and the United Kingdom to the East Coast
of the United States and Canada.
Barnett said his research is important because the search for evidence of
global warming has tended to focus on the atmosphere. But 90 percent of global
warming goes into the Earth's oceans, he said.
Along with his Scripps colleague, David Pierce, Barnett used a combination of
computer models and hard, observed evidence to reach their conclusions. They
determined that warming measured in the world's oceans closely matched the
results predicted in computer models for warming caused by human activity.
When the models assessed whether the ocean warming could be caused by
volcanic or solar activity, Barnett told reporters, the answer was stark: "Not a
Sharon Smith, co-director of the Oceans and Human Health Center at the
University of Miami, said warming is already having an impact on Arctic
ecosystems. She cited a vivid example: In 1997, a highly unusual plant bloomed
in the warming waters of the Bering Sea, changing the color of the water. A bird
called the short-tailed shearwater, which usually locates its prey by sight in
the clear ocean waters, was no longer able to see its prey. Hundreds of
thousands of the birds died, Smith said.
"The present rapid melting of ice is going to disrupt the physical systems
and biological systems that have evolved over long periods of time," Smith told
reporters. And once lost, she added, "it will not come back."
According to Curry, ocean warming is driving a disruption of the Earth's
freshwater balance. Evaporation rates over warmer tropical and subtropical
oceans have increased by about 10 percent in the past 20 years. But instead of
falling over the mid-latitudes of the Northern Hemisphere, it is instead falling
over the far north in North America, Europe and Asia. That at least partly
accounts for a drought in the Western United States and elevated rates of river
runoff in the Arctic.
The inevitable conclusion, Barnett said, is that arguments attacking the
accuracy of climate-model predictions are "no longer tenable." The reality of
global warming is likely to be underscored by changes that millions of people
will feel in their lives.
Models have predicted that the western United States will face a water crisis
within 20 years, he said. Peruvian officials have estimated that with continued
warming, the glaciers of the Andes will be gone within a decade; other estimates
show that two-thirds of the glaciers in Western China could be gone by 2050.
Those developments would leave millions of people without sufficient summer-time
water for drinking, bathing and farming.
The Kyoto climate change treaty went into effect this week for the nations
which signed it. Barnett acknowledged that if the United States had signed it,
the country would have been at a disadvantage against countries like China and
India that were not covered by its terms. But given the environmental trends, he
said, "it's time now for nations that are not part of the Kyoto protocol to
Edward W. Lempinen
17 February 2005