Scientists on AAAS Panel Warn That Ocean Warming Is Having Dramatic Impact

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"Other parts of the world will face similar problems," he added in an unpublished paper released to reporters.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 chance."

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 reconsider."

— Edward W. Lempinen

17 February 2005