Each degree of global warming might ultimately raise global sea levels by more than 2 meters

Press release by the Potsdam Institute for Climate Impact Research 


Greenhouse gases emitted today will cause sea level to rise for centuries to come. Each degree of global warming is likely to raise sea level by more than 2 meters in the future, a study now published in the Proceedings of the National Academy of Sciences shows. While thermal expansion of the ocean and melting mountain glaciers are the most important factors causing sea-level change today, the Greenland and Antarctic ice sheets will be the dominant contributors within the next two millennia, according to the findings. Half of that rise might come from ice-loss in Antarctica which is currently contributing less than 10 percent to global sea-level rise.

“CO2, once emitted by burning fossil fuels, stays an awful long time in the atmosphere,” says Anders Levermann, lead author of the study and research domain co-chair at the Potsdam Institute for Climate Impact Research. “Consequently, the warming it causes also persists.” The oceans and ice sheets are slow in responding, simply because of their enormous mass, which is why observed sea-level rise is now measured in millimeters per year. “The problem is: once heated out of balance, they simply don’t stop,” says Levermann. “We’re confident that our estimate is robust because of the combination of physics and data that we use.”

The study is the first to combine evidence from early Earth’s climate history with comprehensive computer simulations using physical models of all four major contributors to long-term global sea-level rise. During the 20th century, sea level rose by about 0.2 meters, and it is projected to rise by significantly less than two meters by 2100 even for the strongest scenarios considered. At the same time, past climate records, which average sea-level and temperature changes over a long time, suggest much higher sea levels during periods of Earth history that were warmer than present.

For the study now published, the international team of scientists used data from sediments from the bottom of the sea and ancient raised shorelines found on various coastlines around the world. All the models are based on fundamental physical laws. “The Antarctic computer simulations were able to simulate the past five million years of ice history, and the other two ice models were directly calibrated against observational data – which in combination makes the scientists confident that these models are correctly estimating the future evolution of long-term sea-level rise,” says Peter Clark, a paleo-climatologist at Oregon State University and co-author on the study. While it remains a challenge to simulate rapid ice-loss from Greenland and Antarctica, the models are able to capture ice loss that occurs on long time scales where a lot of the small rapid motion averages out.

If global mean temperature rises by 4 degrees compared to pre-industrial times, which in a business-as-usual scenario is projected to happen within less than a century, the Antarctic ice sheet will contribute about 50 percent of sea-level rise over the next two millennia. Greenland will add another 25 percent to the total sea-level rise, while the thermal expansion of the oceans’ water, currently the largest component of sea-level rise, will contribute about 20 percent, and the contribution from mountain glaciers will decline to less than 5 percent, mostly because many of them will shrink to a minimum.

“Continuous sea-level rise is something we cannot avoid unless global temperatures go down again,” concludes Levermann. “Thus we can be absolutely certain that we need to adapt. Sea-level rise might be slow on time scales on which we elect governments, but it is inevitable and therefore highly relevant for almost everything we build along our coastlines, for many generations to come.”

 Article: Levermann, A., Clark, P., Marzeion, B., Milne, G., Pollard, D., Radic, V., Robinson, A. (2013): The multimillennial sea-level commitment of global warming. Proceedings of the National Academy of Sciences (early online edition) [DOI: 10.1073/pnas.1219414110 ]

Weblink to the article once it is published: www.pnas.org/cgi/doi/10.1073/pnas.1219414110

Weblink to the article in open access once it is published: http://www.pnas.org/content/early/recent

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1 Response

  1. Poo says:

    “It will without doubt have come to your Lordship’s knowledge that a considerable change of climate, inexplicable at present to us, must have taken place in the Circumpolar Regions, by which the severity of the cold that has for centuries past enclosed the seas in the high northern latitudes in an impenetrable barrier of ice has been during the last two years, greatly abated,” wrote the president of London’s Royal Society to the British Admiralty in 1817. He went on to state that “new sources of warmth have been opened and give us leave to hope that the Arctic Seas may at this time be more accessible than they have been for centuries past, and that discoveries may now be made in them not only interesting to the advancement of science but also to the future intercourse of mankind and the commerce of distant nations.”

    History trumps the so called climate ‘scientists’ and their models every time. Can none of these people Google? These lads, ever in search of research grants and job security forgo science for alarmism and some sort of statistical significance. It has been said that where one finds a preponderance of statistical significance one also finds junk science full of links and correlations that signify nothing. These folks draw on fallacies to promote their political objectives. In other words, their logic is faulty. Such yelling of impending doom in a theatre would be illegal. Scary climate change news from the likes of Nature Geoscience usually follows a reconstruction of sorts, wild assumptions and much modeling. It is particularly unseemly to read ‘scientists’ predicting in round numbered certainty using such unexacting and unscientific terms as “likely”, “awful long time”, “if” and “a lot.” Their “physical models” and “computer simulations” carry the same errors as all those that came before; you get out what you put in. Better they should be called ‘computer stimulations.’ And people get paid for this? The Climate Change peer review process has been corrupted. It is not peer review at all. Rather, it has become pal review.

    Climate alarmists constantly blame the public’s widespread ignorance of science. There is some truth in this. A scientific grounding wouldn’t hurt any of us but ignorance of history is far more widespread particularly among the alleged ‘scientists.’

    I have long bemoaned the paucity of history taught in our schools these days, but I do expect those that deem themselves ‘scientists’ to be able to Google past the first page. There’s history back there folks, lots of it!

    Even the long named and even longer winded ‘Proceedings of the National Academy of Sciences’ conceded:

    “At the same time, past climate records, which average sea-level and temperature changes over a long time, suggest much higher sea levels during periods of Earth history that were warmer than present.”

    What? “Higher sea levels during periods of Earth history that were warmer than present?” And we’re still here? How could that be? Shouldn’t we be under water or at least up to our knees in it? Well no, when the model fails, make a new one! No one ever raised a dime by saying, “Life is good.” The money is in failure or the threat there of. Money loves misery. I believe in media jargon it is called, “sensationalism.” It very well may sell papers and increase viewership but it gets us not one iota nearer to the truth, which they say is “out there.”

    Let’s start with Greenland, just for a change. Project logistics for the North Greenland Eemian Ice Drilling (NEEM) project are managed by Denmark’s Centre for Ice and Climate. The Arctic Sciences Section in the National Science Foundation’s Division of Polar Programs manages the U.S. support. In addition to Denmark and the U.S. researchers from Belgium, Canada, China, France, Germany, Iceland, Japan, the Netherlands, South Korea, Sweden, Switzerland and the United Kingdom are also partners in NEEM. It’s a big, well funded group and its findings are unexpected or should I say unplanned?

    The research published 1/24/13 shows that during the Eemian interglacial period (about 130,000 years ago, ending about 115,000 years ago) the climate in North Greenland was about 8 degrees Celsius warmer than at present. The seas at that time were roughly four to eight meters higher than they are today. The surface in the vicinity of NEEM was only a few hundred meters lower than its present level, which indicates that the Greenland ice sheet may have contributed less than half of the total sea rise at the time.

    “The new findings reveal higher temperatures in Northern Greenland during the Eemian than paleo-climate models have estimated,” said Dorthe Dahl-Jensen, of the University of Copenhagen, the NEEM project leader. Imagine that, the models were wrong!

    How about the Arctic and its melting ice? Arctic ice melt is a natural cycle that has occurred in the past and will occur again. Arctic sea ice loss is also matched by Antarctic sea ice gain. Let us not forget that the melting glaciers off Newfoundland a century ago produced the iceberg that sunk the Titanic. Tourists stream every year to Iceberg Alley off the coast of Newfoundland. This is well documented and shreds speculations from the alarmists that the Arctic is only now warming, or that temperatures had been relative stable over the past one or two thousand years, and only in the last century climbed dramatically. Arctic sea ice loss in the 1940s was similar to what we are experiencing today.

    “If we could look back at this region of Antarctica in the 1940s and 1830s, we would find that the regional climate would look a lot like it does today, and I think we also would find the glaciers retreating much as they are today,” said lead author Eric Steig of the University of Washington.

    Icebergs break off Antarctic glaciers because that is what they do. Icebergs break off glaciers, live with it. Since the mid 1950s the U.S. has maintained a continual base at the South Pole. The temperatures it has recorded are colder today than when it was first established more than 50 years ago.

    Never mind 130,000 years ago. The Medieval Warm Period was warmer as have been most of the last 10,000 years. Alaska’s record high 110 F was set in in 1915. It hasn’t significantly warmed since 1998 in fact, a solid argument can be made that it is actually cooling.

    I have repeatedly mentioned the necessary warming that occurred between Ice Ages and the mere 163 years (less than a finger snap in time) since the end of the Little Ice Age in 1850. How bad was that? I have mentioned before that the Thames, Seine and Hudson froze over. Unlikely to be repeated as all have been banked, built upon and narrowed so that they now flow too fast, at least in the most urban areas.

    In North America, the early European settlers reported exceptionally severe winters during the Little Ice Age. In 1607-1608, ice persisted on Lake Superior until June. In 1686, James Bay was still littered with floating ice in the month of July 1.

    About one-quarter of Lake Ontario will freeze over in any given year. Shallower Lake Erie can see a 90 per cent covering of ice. In the winter of 1933-34, however, Lake Ontario froze over completely. The ice was measured at 2’ thick in some places. You could have walked from Toronto to Rochester, N.Y. The news was so big it made the New York Times. We’ve got to do a lot here in order to achieve that!

    It is suspected that Lake Ontario “nearly” froze again in the late 1970s and again in 1993. Other less reliable stories have it freezing across in 1912, 1893, 1874 and 1855.

    What are the odds of it happening again?
    What about climate change? With the warmer winters we have experienced in recent years, could Lake Ontario ever completely freeze over again? Environment Canada’s Dave Phillips says he still believes it’s possible. “Forces will still sometimes come together to create the conditions. Yes, I think it could happen again.”

    What are the odds of it happening again?

    The CIS (Canada Ice Services), rates the odds this way: Erie, the shallowest and farthest south of the lakes, is the most likely to freeze to that point, with a chance of 69 per cent. Huron comes next at a 22-per-cent probability, followed by Superior at 17 per cent and Michigan at 11 per cent. Due to currents, it is estimated that Lake Ontario has a mere 1-in-100 chance of having 90-per-cent ice coverage.

    Guess they are not expecting it to get too much warmer. Okay, in time we hit the sun but until then Canada will still face 8 months of winter and 4 months of bad sledding.

    Pictures of polar bears are cute and guaranteed money raisers but their numbers are increasing. We should know, 2/3 of the world’s population resides in Canada. Some, like the King of the Hypocrites Al Gore, say Polar Bears are threatened but they have seen an increase here of some 300% since the 1950s. The scientific name for Polar bears is Ursus Maritimus, which means sea bear. They swim! In fact, they are excellent swimmers and can swim 200 miles or more with little effort. Ask any Inuit hunter. A Polar Bear with a radio tracking collar once swam over 400 miles in 9 days without rest. They have even survived periods when the Arctic melted completely in the past. They moved to land where they go to mate in any case as well as eat blueberries, their favorite dish next to seals.

    Sea level rise predictions, based upon model after error prone model, are exaggerated. Record high snow cover levels were set in the winter of 2008/2009 yet the sea level fell in 2010.

    Europe and Asia, are replete with written accounts of how changes in temperature affected what crops could be grown and, moreover, where people could live. The Romans conquered a much warmer world than exists today. 1,000 years ago (the Medieval Warm Period) grapes and citrus trees grew in Britain, Scandanavians farmed in Greenland and olives grew in Germany.

    Please do not get me started on floods that occur on Flood Plains or ocean waves that wreck havoc on homes built at sea level and below. I note with amusement how reports ignore history by constantly using the phrase, “worst in 50 years.” A modest history lesson is much more useful than alarmist yammering science which is far more speculative than fact, modeled and politicized to enhance the ultimate truth, the eternal quest for more grant money. Yes we’ve seen droughts but nothing to compare with the Dust Bowl (Dirty 30s) which caused major ecological and agricultural damage to American and Canadian prairie lands in the 1930s. Yet another climate event that finds itself outside the 50 year limit.

    At the end of the Little Ice Age, sometime during the 1850s, Canadians invented the game of hockey. This was before there actually was a Canada. Hey, we’ve got our priorities straight!

    As for the rest of the modelers and their prognostications, I am reminded of another quote, author unknown.

    “A fool can put on his coat better than a wise man can put it on for him.”

    Make that a “fool” with some knowledge of history or the ability to Google the pages that are to be found beyond the first one.

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