Polar Ice Sheets Melt at Faster Pace

WSJ, By Gautam Naik, November 29

Higher temperatures over the past two decades have caused the polar ice sheets to melt at an accelerating rate, contributing to an almost half-inch rise in global sea levels, according to the most comprehensive study done so far.

Scientists long have struggled to get a fix on whether the permanent ice sheets of Greenland and Antarctica are gaining or losing ice. Past satellite-based measurements either were limited in scope or suffered from methodological inconsistencies.

The study, published Thursday in the journal Science, estimates that the melting of the ice sheets has raised global sea levels by 11.1 millimeters (0.43 inches) since 1992. That represents one-fifth of the total sea-level increase recorded in that period.

In the 1990s, melting of the polar ice sheets was responsible for about 10% of the global sea-level rise, but now it represents about 30%, the data suggest.

[...]

“If you extrapolate these results, Greenland is going to be a serious contributor to global sea level rise” in coming years, said Peter Wadhams, a professor of ocean physics at the University of Cambridge, England, who wasn’t involved in the Science study. “Its contribution, relative to other sources, is becoming greater and greater.”

[...]

The latest effort reconciles the differences among dozens of earlier measurements and includes new data to compile an estimate that is believed to be twice as accurate as previous ones, according to researchers involved.

“It allows us to make some firm conclusions,” said Andrew Shepherd, a professor of earth observation at the University of Leeds in England and a lead author of the study. “It wasn’t clear if Antarctica was gaining or losing ice. Now we can say with confidence it is losing ice.”


Science Magazine – Commentary summary:

Experts Agree Global Warming Is Melting the World Rapidly

Science, By Richard A. Kerr, November 30

Forty-seven glaciologists have arrived at a community consensus over all the data on what the past century’s warming has done to the great ice sheets: a current annual loss of 344 billion tons of glacial ice, accounting for 20% of current sea level rise. Greenland’s share—about 263 billion tons—is roughly what most researchers expected, but Antarctica’s represents the first agreement on a rate that had ranged from a far larger loss to an actual gain. The new analysis, published on page 1183 of this week’s issue of Science, also makes it clear that losses from Greenland and West Antarctica have been accelerating, showing that some ice sheets are disconcertingly sensitive to warming.


Update – Links:
Climate Progress: Scientific American: ‘Loss of Ice, Melting Of Permafrost And Other Climate Effects Are Occurring At An Alarming Pace’
Climate Progress: Study: Sea Levels Rising 60% Faster Than Projected, Planet Keeps Warming As Expected
Climate Progress: Watch: Self-Described Climate Skeptic Says She’s Changed By ‘Chasing Ice’ Documentary
Climate Progress: Rep. Lamar Smith, Who Criticized ‘The Idea Of Human-Made Global Warming,’ Set To Chair House Science Panel
Climate Progress: November 28 News: IEA Chief Economist Sees ‘No Momentum’ For International Progress On Climate
The Guardian: Greenland and Antarctica ‘have lost 4tn tonnes of ice’ in 20 years

The scientists claim the study, published in the journal Science, ends a long-running debate over whether the vast ice sheet covering the Antarctic continent is losing or gaining mass. East Antarctica is gaining some ice, the satellite data shows, but west Antarctica and the Antarctic peninsula is losing twice as much, meaning overall the sheet is melting.

Climate Progress: Science Stunner: Greenland Ice Melt Up Nearly Five-Fold Since Mid-1990s, Antartica’s Ice Loss Up 50% In Past Decade
University of Wyoming: UW Professor’s Delayed Greenland Ice Melt Research Published in Nature

“There’s been a lot of media hype about the melting of Greenland. It’s caught the public’s imagination,” he says. “Other than the media, scientists have been predicting significant amounts of snowmelt will occur quickly in Greenland.”

However, despite the snowmelt, the meltwater runoff will not be so fast, according to Humphrey’s research.

Climate Progress: House Committee Leaders Deny Climate Change While Extreme Weather Devastates Their States

4 comments to Polar Ice Sheets Melt at Faster Pace

  • Human-Caused Climate Change Signal Emerges from the Noise

    By comparing simulations from 20 different computer models to satellite observations, Lawrence Livermore climate scientists and colleagues from 16 other organizations have found that tropospheric and stratospheric temperature changes are clearly related to human activities.

    No known mode of natural climate variability can cause sustained, global-scale warming of the troposphere and cooling of the lower stratosphere.

  • Raja

    Study: Carbon dioxide emissions worldwide up again, 2-degree limit to global warming unlikely

    AP, December 2

    Washington — The amount of heat-trapping pollution the world spewed rose again last year by 3 percent. So scientists say it’s now unlikely that global warming can be limited to a couple of degrees, which is an international goal.

    The overwhelming majority of the increase was from China, the world’s biggest carbon dioxide polluter. Of the planet’s top 10 polluters, the United States and Germany were the only countries that reduced their carbon dioxide emissions.

    Last year, all the world’s nations combined pumped nearly 38.2 billion tons of carbon dioxide into the air from the burning of fossil fuels such as coal and oil, according to new international calculations on global emissions published Sunday in the journal Nature Climate Change. That’s about a billion tons more than the previous year.

    [...]

    Andrew Weaver, a climate scientist at the University of Victoria in Canada who was not part of the study, said: “We are losing control of our ability to get a handle on the global warming problem.”

    The biggest polluters in 2011 were: China (up 10% yoy), United States (down 2% yoy), India, Russia, Japan, Germany, Iran, South Korea, Canada and South Africa. – Raja


    World temperature set to increase 9 [Fahrenheit] degrees: study

    Agence France-Presse, December 2

    Paris — Levels of atmospheric carbon dioxide (CO2) are rising annually by around three percent, placing Earth on track for warming that could breach five degrees Celsius (9.0 degrees Fahrhenheit) by 2100, a new study published on Sunday said.

    The figure — among the most alarming of the latest forecasts by climate scientists — is at least double the 2C (3.6F) target set by UN members struggling for a global deal on climate change.

    In 2011, global carbon emissions were 54 percent above 1990 levels, according to the research, published in the journal Nature Climate Change by the Global Carbon Project consortium.

    “We are on track for the highest emissions projections, which point to a rise in temperature of between 4C (7.2F) and 6C (10.8F) by the end of the century,” said Corinne le Quere, a carbon specialist at the University of East Anglia, eastern England.

    [...]

    Last year, Chinese CO2 rose by 10 percent, or more than 800 million tonnes, equivalent to Germany’s emissions in an entire year, said the Center for International Cimate and Environmental Research – Oslo (CICERO), whose scientists took part in the paper.

    “China is emitting as much as the European Union on a per-capita basis, about 36 percent higher than the global average per-capita emissions,” it said in a press release.


    Nature Climate Change: The challenge to keep global warming below 2 °C

    The latest carbon dioxide emissions continue to track the high end of emission scenarios, making it even less likely global warming will stay below 2 °C. A shift to a 2 °C pathway requires immediate significant and sustained global mitigation, with a probable reliance on net negative emissions in the longer term.

  • Raja

    IPCC’s Planned Obsolescence: Fifth Assessment Report Will Ignore Crucial Permafrost Carbon Feedback!

    Climate Progress, By Joe Romm, December 2

    A key reason the Intergovernmental Panel on Climate Change keeps issuing instantly irrelevant reports is that it keeps ignoring the latest climate science. We have known for years that perhaps the single most important carbon-cycle feedback is the melting of the permafrost.

    Yet a must-read new United Nations Environment Programme report, “Policy Implications of Warming Permafrost” [PDF] reports this jaw-dropping news:

    The effect of the permafrost carbon feedback on climate has not been included in the IPCC Assessment Reports. None of the climate projections in the IPCC Fourth Assessment Report include the permafrost carbon feedback (IPCC 2007). Participating modeling teams have completed their climate projections in support of the Fifth Assessment Report, but these projections do not include the permafrost carbon feedback. Consequently, the IPCC Fifth Assessment Report, due for release in stages between September 2013 and October 2014, will not include the potential effects of the permafrost carbon feedback on global climate.

    Here’s why that is head-exploding.

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