Arctic temperatures near a prehistoric level when seas were 16 to 20 feet higher, studies say.

Global warming appears to be pushing vast reservoirs of ice on Greenland and Antarctica toward a significant, long-term meltdown. The world may have as little as a decade to take the steps to avoid this scenario.

Those are the implications of new studies that looked to climate history for clues about how the planet's major ice sheets might respond to human-triggered climate change.

Already, temperatures in the Arctic are close to those that thawed much of Greenland's ice cap some 130,000 years ago, when the planet last enjoyed a balmy respite from continent-covering glaciers, say the studies' authors.

By 2100, spring and summer temperatures in the Arctic could reach levels that trigger an unstoppable repeat performance, they say. Over several centuries, the melt could raise sea levels by as much as 20 feet, submerging major cities worldwide as well as chains of islands, such as the present-day Bahamas.

The US would lose the lower quarter of Florida, southern Louisiana up to Baton Rouge, and North Carolina's Outer Banks. The ocean would even flood a significant patch of California's Central Valley, lapping at the front porches of Sacramento.

These estimates may understate the potential rise. The teams say their studies provide the first hints that during the last interglacial period, ice sheets in both hemispheres worked together to raise sea levels, rather than the Northern Hemisphere's ice alone. This raises concerns that Antarctic melting might be more severe this time, because additional melt mechanisms may be at work.

"It sounds bad," acknowledges Jonathan Overpeck, a University of Arizona researcher who led one of the two studies. He notes that rising temperatures are approaching a threshold. But "we know about it far enough in advance to avoid crossing it." The challenge, he and others say, is to take advantage of the remaining window by reducing emissions of greenhouse gases substantially.

The two studies were published in Friday's issue of the journal Science.

Ice on Greenland and Antarctica is already thinning faster than it's being replaced - and faster than scientists thought it would, notes Richard Alley, a paleoclimatologist at Penn State University and member of one of the research teams. Only five years ago, he notes, climate scientists expected the ice sheets to gain mass through 2100, then begin to melt. "We're now 100 years ahead of schedule," he says.

The new results aren't the end of the story. The researchers will refine the models, improve the measurements, and find other sources of data to verify the modeling. Coral data pointing to sea-level changes in the last warm period remain controversial, the team acknowledges. And the team's assumption that the amount of carbon dioxide would triple by 2100, although moderate among climate forecasts, is not a done deal. It depends on how quickly industrial and developing countries adopt low-emission technologies and take long-term steps to reduce greenhouse gases.

But the window for action is relatively short, Dr. Overpeck says. CO2 remains in the atmosphere for more than a century after it's first emitted. And it takes time to implement policies and adopt technologies. Thus for all practical purposes, the tipping point may come sooner than atmospheric chemistry would suggest.

The studies required some in-depth sleuthing. Researchers realized that changes in Earth's tilt and orbit intensified the sunlight reaching the Arctic during interglacial periods, notes Bette Otto- Bliesner, a scientist at the National Center for Atmospheric Research in Boulder, Colo. But when it came to the effect on the Arctic's ice, "no one knew how big the response would be."

So she and her colleagues first tested the center's newest climate model against temperature information gleaned from pollen, insects, ocean plankton, and other remnants of the period. The results matched closely.

Confident that they could reproduce the period's climate by computer, they linked the results to a second model with a reputation for accurately simulating ice sheets. Using ice-core samples and other evidence as a reality check, they concluded that within 1,000 to 2,000 years of the warming's onset, Greenland's ice sheet dwindled to a steep lump covering the island's central and northern parts. The melt water raised sea levels by seven to 11 feet.

But coral records from geologically stable parts of the ocean suggested that sea levels during that time rose 16 to 20 feet - a level that held for roughly 11,000 years. Overpeck, who had been working with Dr. Otto-Bliesner on the initial modeling exercise, says several lines of evidence led him to suspect that the balance came from Antarctica.

From there, the team used the climate model to estimate the warming that could occur by 2130 if CO2 emissions rose by 1 percent per year. In the pantheon of emissions scenarios, this represents a moderate one, he holds. But it's enough to triple CO2 concentrations by 2100, leading to summers that are 5 to 8 degrees F. warmer than today - levels that appear to have melted the ice 129,000 years ago.


 

An Arctic Alert on Global Warming

Source: Christian Science Monitor (US)
Author: Peter N. Spotts, Staff Writer of The CSM
Published: November 09, 2004 Edition 
Copyright: 2004 The Christian Science Monitor
Contact: oped@csps.com
Website: http://www.csmonitor.com/

Global warming is heating the Arctic at a rapid pace - with impacts that could range from the disappearance of polar bears' summer habitat by the century's end to a damaging rise in sea levels worldwide. 

That assessment, released Monday by a group of international climate experts, amounts to one of the most urgent warnings on climate change to date, and could put new pressure on the US and other nations to curb fossil-fuel emissions.

This comes at a time of growing concern about the effects of global warming, which scientists generally agree is increasingly driven by rising carbon-dioxide levels in the atmosphere from human industrial activity and changing land-use patterns.

Monday's report called for "strong near-term action" to reduce output of gases that, when they rise into the atmosphere, trap heat in what is called the greenhouse effect.

The trends cited in the Arctic Climate Impact Assessment are stark:

• Rapid melting of Arctic glaciers, including the vast sheet of ice that covers Greenland. The sheet locks up enough fresh water to raise sea levels by as much as 27 feet over the course of several centuries. The group calculates that during this century, Greenland temperatures are likely to exceed the threshold for triggering the long-term meltdown of the island's ice sheet.

• Arctic temperatures rising up to twice as fast as the global average. Over the past 50 years, average winter temperatures in Alaska, western Canada, and eastern Russia have risen as much as 7 degrees F. Over the next century, temperatures are projected to rise by up to 13 degrees F.

• A dramatic reduction in the extent of the summer ice pack in the Arctic Ocean. Late-summer ice coverage already has declined by as much as 20 percent over the past three decades. The summer ice pack is projected to shrink by another 10 to 50 percent by the end of the century. Some climate models show the summer ice vanishing by 2040.

Either change could accelerate warming by allowing the ocean to absorb solar heat. The change could threaten species such as polar bears and some seals with extinction. Researchers also worry that an influx of fresh water into the North Atlantic could disrupt large-scale ocean currents worldwide, altering weather patterns and the locations where nutrients rise from the depths to support regional fisheries.

"The Arctic is warming now, at a faster rate than the rest of the planet. It's affecting people, and its effects are global," says Robert Corell, a senior fellow with the American Meteorological Society who chaired the team that pulled the study together.

Assembled over 4-1/2 years, the study came at the request of the Arctic Council and the International Arctic Science Committee. The council includes top-level government officials from the United States, Canada, Denmark, Finland, Iceland, Norway, Russia, and Sweden, as well as from six organizations representing indigenous groups who live in the Arctic region. Some 300 scientists from the world's top polar-research centers were involved.

The report details current and projected changes that could affect everything from shipping, agriculture, and the livelihoods of indigenous people to breeding grounds for migratory birds, many of which are considered endangered. One aspect on which researchers are keeping their eye: the release of methane and carbon dioxide as permafrost thaws and tundra decomposes. Even if the advance of forests to higher latitudes soaks up some of this released CO2, this still leaves methane - a much more potent greenhouse gas - free to enter the atmosphere.

Monday, the Pew Center on Global Climate Change issued its own study of global warming's effect on the US. The report largely focuses on warming's impact on ecology and biodiversity.

The Arctic study also comes at a time of growing momentum internationally to address the climate change.

Last week, Russian President Vladimir Putin signed a bill passed by parliament that ratified the 1997 Kyoto Protocol. His signature was the final act required for the pact to take effect. The accord requires industrial countries party to the pact to reduce their CO2 emissions by an average of 5.5 percent between 2008 and 2012. While climate researchers agree that the pact's target will have little effect on atmospheric CO2, the agreement establishes mechanisms for achieving emissions targets, such as emissions trading, that may be a foundation for future agreements.

Perhaps just as important, supporters say, once the protocol takes force, it requires countries to begin looking ahead to follow-on agreements that would have a more significant impact on emissions.

In a statement released following Mr. Putin's signing, Eileen Claussen of the Pew Center on Climate Change noted that talks are set to begin next year on a post-Kyoto agreement. Now that the protocol is in effect, it "sets the stage for a new round of negotiations that can produce a broader, more durable agreement," she said. "New approaches will be needed to better engage the United States and major developing countries in the ... effort."

The new report is likely to add to pressure building on the Bush administration to take firmer actions to curb America's carbon emissions. British Prime Minister Tony Blair has signaled that climate will be one of his top priorities when he takes over as president of the G-8 group of industrial nations in January.

In a recent interview with Reuters, David King, Britain's chief science adviser, noted that during the summer, White House policymakers "fully accepted the scientific arguments for climate change and are keen to play a leadership role. So far we've been focusing on Russia. Clearly now the spotlight is going to move."

President Bush withdrew the US from the Kyoto treaty in 2001. The administration has said it views global warming as a serious threat, but that the Kyoto approach puts too much of the carbon-reduction burden on the US and other industrial countries, putting millions of jobs at risk.

The administration is spending several billion dollars each year to research technologies such as clean-burning coal and hydrogen-fueled cars. And while Bush hasn't signed on to the Kyoto goals, the administration talks of reducing the economy's "carbon-intensity" - the amount of carbon needed to produce each dollar of economic output.

"It is of importance to the president that we continue to make progress" on climate change, EPA administrator Mike Leavitt told the Associated Press Friday.

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Websites and Organizations:

Sierra Club Global Warming Page
Includes information on the health hazards of global warming, facts on SUVs and pollution, vanishing wildlife and habitat and clean energy alternatives.

Climate Hot Map
A click able map that shows the local effects of climate change around the world, sponsored by the World Wildlife Fund, Sierra Club, and other nonprofit environmental groups.

United States Global Change Research Information Office
The US Global Change Research Information Office (GCRIO) is a clearinghouse for key documents generated or sponsored by federal agencies. Many important policy papers generated by the United States government can be found at their website.

Global Warming and Climate Change Policy WWW Sites
Extensive links to sites focusing on global warming policy around the world.

Environmental Defense: Sea Level Rise in the NYC Area - in PDF Format
Eye-opening maps that show the damaging effects of sea level rise in Manhattan and Long Island, New York.

Pew Center on Global Climate Change
The Pew Center's objectives are to educate the public and key policy makers about the causes and potential consequences of climate change, and to encourage the domestic and international community to reduce emissions of greenhouse gases. An independent, nonpartisan organization, they work with major corporations and release reports on environmental impacts, economics and policy issues.

Public Interest Research Group (PIRG) Global Warming Campaign
Find out what PIRG is doing to fight global warming in their Earth Day Clean Energy Agenda.

American Council for an Energy Efficient Economy
A nonprofit organization dedicated to advancing energy efficiency as a means of promoting both economic prosperity and environmental protection, the ACEEE advises policymakers and educates consumers and businesses about saving energy and cutting pollution.

Global Climate Coalition
The Global Climate Coalition is "an organization of trade associations established to coordinate business participation in the international policy debate on the issue of global climate change and global warming." This group includes some of the world's most powerful corporations involved with fossil fuels and has been said to be a dominant player in undermining U.S. leadership in Kyoto.

National Center for Atmospheric Research
The NCAR serves as a focus for research on atmospheric and related science problems makes scientific contributions to understanding the earth system, including ozone depletion, climate change and severe storms.

Union of Concerned Scientists
Founded in 1969 by faculty members and students at the Massachusetts Institute of Technology who were concerned about the misuse of science and technology in society, UCS is an independent nonprofit alliance of 50,000 concerned citizens and scientists across the country who augment rigorous scientific analysis with citizen advocacy to build a cleaner, healthier environment and a safer world.

Climate Action Network
The Climate Action Network (CAN) is a global network of over 287 Non- Governmental Organizations (NGOs) working to promote government and individual action to limit human-induced climate change to ecologically sustainable levels. Contains loads of links and resources on key issues pertaining to climate change.

Goddard Institute for Space Studies (GISS)
This NASA research institute is one of the world's leading centers for climate modeling. Its scientists have done pioneering work on such topics as implications of volcanoes and other producers of sulfate aerosols on climate, implications of global warming for drought incidence and severity and implicatoins of climate change for agricultural productivity and food security.