Keyword Tag Sort by

Categories: Atmospheric Science Environment Global warming Greenhouse Gases

Global Warming: Cuts in Greenhouse Gas Emissions Would Save Arctic Ice, Reduce Sea Level Rise

BOULDER—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."


Warren Washington. (©UCAR, photo by Carlye Calvin.) [ENLARGE]

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.


2 global maps using color scale to indicate warming

New computer simulations show the extent that average air temperatures at Earth's surface could warm by 2080-2099 compared to 1980-1999, if (top) greenhouse gases emissions continue to climb at current rates, or if (bottom) society cuts emissions by 70 percent. In the latter case, temperatures rise by less than 2°C (3.6°F) across nearly all of Earth's populated areas. However, unchecked emissions could lead to warming of 3°C (5.4°F) or more across parts of Europe, Asia, North America, and Australia. (Graphic courtesy Geophysical Research Letters, modified by UCAR.) [ENLARGE]

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."


About the article

Title: "How Much Climate Change Can Be Avoided by Mitigation?"
Authors: Warren Washington, Reto Knutti, Gerald Meehl, Haiyan Teng, Claudia Tebaldi, David Lawrence, Lawrence Buja, Gary Strand
Publication: Geophysical Research Letters


Gerald Meehl, NCAR Senior Scientist

Reto Knutti, Scientist, Institute for Atmospheric and Climate Science (Zurich, Switzerland)

Source: The University Corporation for Atmospheric Research (UCAR),  The National Center for Atmospheric Research (NCAR)

Related News:

Consequential Life Cycle Assessment of Nitrogen Fertilisers Based... 27 November 2012, 06:33
Abstract: The production of mineral nitrogen represents a large fossil energy input in Swedish...

Earth Sunblock Only Needed If Planet Warms Easily 11 October 2012, 14:51
Planet's sensitivity to greenhouse gases will determine how much shading could be needed to...

Man already contributed to greenhouse gases in Roman times 8 October 2012, 03:17
Air bubbles in ancient ice cores provide proof.The influence of humans on the emissions of the...

New Data on the Biofuel Ecobalance: Most Biofuels Are Not “Green” 24 September 2012, 05:09
Duebendorf, St. Gall, Thun, 24 September 2012-- First tops, then flops. That is one way of...

Scientific discovery offers 'green' solution in fight... 24 September 2012, 03:27
A low-cost new material that could lead to innovative technologies to tackle global warming has...

Two degrees is too much for most coral reefs 17 September 2012, 05:43
A modelling study from an international collaboration involving German, Canadian and Australian...

Nano-Velcro Clasps Heavy Metal Molecules in its Grips 10 September 2012, 03:45
10.09.12 - Researchers develop nano-strips for inexpensive testing of mercury levels in our...

Global Warming Harms Lakes 16 July 2012, 12:10
Global warming also affects lakes. Based on the example of Lake Zurich, researchers from the...

Research Shows Humans are Primary Cause of Global Ocean Warming... 11 June 2012, 03:36
The oceans have warmed in the past 50 years, but not by natural events alone.LIVERMORE, Calif. --...

Corals 'Could Survive a More Acidic Ocean' 2 April 2012, 05:35
Corals may be better placed to cope with the gradual acidification of the world’s oceans than...