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Global Warming: Cuts in Greenhouse Gas Emissions Would Save Arctic Ice, Reduce Sea Level Rise
April 15, 2009BOULDER-The threat of global warming can still be greatly diminished if nations cut emissions of heat-trapping greenhouse gases by 70 percent this century, according to a new analysis. While global temperatures would rise, the most dangerous potential aspects of climate change, including massive losses of Arctic sea ice and permafrost and significant sea level rise, could be partially avoided.
The study, led by scientists at the National Center for Atmospheric Research (NCAR), will be published next week in Geophysical Research Letters. It was funded by the Department of Energy and the National Science Foundation, NCAR's sponsor.
"This research indicates that we can no longer avoid significant warming during this century," says NCAR scientist Warren Washington, the lead author. "But if the world were to implement this level of emission cuts, we could stabilize the threat of climate change and avoid catastrophe."
Avoiding dangerous climate change
Average global temperatures have warmed by close to 1 degree Celsius (almost 1.8 degrees Fahrenheit) since the pre-industrial era. Much of the warming is due to human-produced emissions of greenhouse gases, predominantly carbon dioxide. This heat-trapping gas has increased from a pre-industrial level of about 284 parts per million (ppm) in the atmosphere to more than 380 ppm today.
With research showing that additional warming of about 1 degree C (1.8 degrees F) may be the threshold for dangerous climate change, the European Union has called for dramatic cuts in emissions of carbon dioxide and other greenhouse gases. The U.S. Congress is also debating the issue.
To examine the impact of such cuts on the world's climate, Washington and his colleagues ran a series of global supercomputer studies with the NCAR-based Community Climate System Model. They assumed that carbon dioxide levels could be held to 450 ppm at the end of this century. That figure comes from the U.S. Climate Change Science Program, which has cited 450 ppm as an attainable target if the world quickly adapts conservation practices and new green technologies to cut emissions dramatically. In contrast, emissions are now on track to reach about 750 ppm by 2100 if unchecked.
The team's results showed that if carbon dioxide were held to 450 ppm, global temperatures would increase by 0.6 degrees C (about 1 degree F) above current readings by the end of the century. In contrast, the study showed that temperatures would rise by almost four times that amount, to 2.2 degrees C (4 degrees F) above current readings, if emissions were allowed to continue on their present course.
Holding carbon dioxide levels to 450 ppm would have other impacts, according to the climate modeling study:
* Sea level rise due to thermal expansion as water temperatures warmed would be 14 centimeters (about 5.5 inches) instead of 22 centimeters (8.7 inches). Significant additional sea level rise would be expected in either scenario from melting ice sheets and glaciers.
* Arctic ice in the summertime would shrink by about a quarter in volume and stabilize by 2100, as opposed to shrinking at least three-quarters and continuing to melt. Some research has suggested the summertime ice will disappear altogether this century if emissions continue on their current trajectory.
* Arctic warming would be reduced by almost half, helping preserve fisheries and populations of sea birds and Arctic mammals in such regions as the northern Bering Sea.
* Significant regional changes in precipitation, including decreased precipitation in the U.S. Southwest and an increase in the U.S. Northeast and Canada, would be cut in half if emissions were kept to 450 ppm.
* The climate system would stabilize by about 2100, instead of continuing to warm.
The research team used supercomputer simulations to compare a business-as-usual scenario to one with dramatic cuts in carbon dioxide emissions beginning in about a decade. The authors stressed that they were not studying how such cuts could be achieved nor advocating a particular policy.
"Our goal is to provide policymakers with appropriate research so they can make informed decisions," Washington says. "This study provides some hope that we can avoid the worst impacts of climate change--if society can cut emissions substantially over the next several decades and continue major cuts through the century."
The University Corporation for Atmospheric Research
Avoiding dangerous climate change
Average global temperatures have warmed by close to 1 degree Celsius (almost 1.8 degrees Fahrenheit) since the pre-industrial era. Much of the warming is due to human-produced emissions of greenhouse gases, predominantly carbon dioxide. This heat-trapping gas has increased from a pre-industrial level of about 284 parts per million (ppm) in the atmosphere to more than 380 ppm today.
With research showing that additional warming of about 1 degree C (1.8 degrees F) may be the threshold for dangerous climate change, the European Union has called for dramatic cuts in emissions of carbon dioxide and other greenhouse gases. The U.S. Congress is also debating the issue.
To examine the impact of such cuts on the world's climate, Washington and his colleagues ran a series of global supercomputer studies with the NCAR-based Community Climate System Model. They assumed that carbon dioxide levels could be held to 450 ppm at the end of this century. That figure comes from the U.S. Climate Change Science Program, which has cited 450 ppm as an attainable target if the world quickly adapts conservation practices and new green technologies to cut emissions dramatically. In contrast, emissions are now on track to reach about 750 ppm by 2100 if unchecked.
The team's results showed that if carbon dioxide were held to 450 ppm, global temperatures would increase by 0.6 degrees C (about 1 degree F) above current readings by the end of the century. In contrast, the study showed that temperatures would rise by almost four times that amount, to 2.2 degrees C (4 degrees F) above current readings, if emissions were allowed to continue on their present course.
Holding carbon dioxide levels to 450 ppm would have other impacts, according to the climate modeling study:
* Sea level rise due to thermal expansion as water temperatures warmed would be 14 centimeters (about 5.5 inches) instead of 22 centimeters (8.7 inches). Significant additional sea level rise would be expected in either scenario from melting ice sheets and glaciers.
* Arctic ice in the summertime would shrink by about a quarter in volume and stabilize by 2100, as opposed to shrinking at least three-quarters and continuing to melt. Some research has suggested the summertime ice will disappear altogether this century if emissions continue on their current trajectory.
* Arctic warming would be reduced by almost half, helping preserve fisheries and populations of sea birds and Arctic mammals in such regions as the northern Bering Sea.
* Significant regional changes in precipitation, including decreased precipitation in the U.S. Southwest and an increase in the U.S. Northeast and Canada, would be cut in half if emissions were kept to 450 ppm.
* The climate system would stabilize by about 2100, instead of continuing to warm.
The research team used supercomputer simulations to compare a business-as-usual scenario to one with dramatic cuts in carbon dioxide emissions beginning in about a decade. The authors stressed that they were not studying how such cuts could be achieved nor advocating a particular policy.
"Our goal is to provide policymakers with appropriate research so they can make informed decisions," Washington says. "This study provides some hope that we can avoid the worst impacts of climate change--if society can cut emissions substantially over the next several decades and continue major cuts through the century."
The University Corporation for Atmospheric Research
Sea Level Rise Current Events and Sea Level Rise News RSSDiverting sediment-rich water below New Orleans could lead to extensive new land
Diverting sediment-rich water from the Mississippi River below New Orleans could generate new land in the river's delta in the next century.
Cuts to Mississippi levees could build new land in sinking delta
Diverting sediment-rich water from the Mississippi River below New Orleans could generate new land in the river's delta in the next century that would equal almost half the acreage otherwise expected to disappear during that period, a new study shows.
NASA flies to Antarctica for largest airborne polar ice survey
NASA begins a series of flights Oct. 15 to study changes to Antarctica's sea ice, glaciers and ice sheets. The flights are part of Operation Ice Bridge, a six-year campaign that is the largest airborne survey ever made of ice at Earth's polar regions.
World's river deltas sinking due to human activity, says new study led by CU-Boulder
A new study led by the University of Colorado at Boulder indicates most of the world's low-lying river deltas are sinking from human activity, making them increasingly vulnerable to flooding from rivers and ocean storms and putting tens of millions of people at risk.
Carnegie Institution
The future of the Earth could rest on potentially dangerous and unproven geoengineering technologies unless emissions of carbon dioxide can be greatly reduced, a new study has found.
Antarctic glacier thinning at alarming rate
The thinning of a gigantic glacier in Antarctica is accelerating, scientists warned today. The Pine Island Glacier in West Antarctica, which is around twice the size of Scotland, is losing ice four times as fast as it was a decade years ago.
New predictions for sea level rise
Fossil coral data and temperature records derived from ice-core measurements have been used to place better constraints on future sea level rise, and to test sea level projections.
Study: Greenland ice sheet larger contributor to sea-level rise
The Greenland ice sheet is melting faster than expected according to a new study led by a University of Alaska Fairbanks researcher and published in the journal Hydrological Processes.
Lesson from the past for surviving climate change
Research led by the University of Leicester suggests people today and in future generations should look to the past in order to mitigate the worst effects of climate change.
Melting Greenland Ice Sheets May Threaten Northeast United States, Canada
Melting of the Greenland ice sheet this century may drive more water than previously thought toward the already threatened coastlines of New York, Boston, Halifax, and other cities in the northeastern United States and Canada.
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