The rest of the media is finally catching up to my post from last month.
That’s because Nature published the peer-reviewed paper that was first reported at the American Geophysical Union meeting and Nature‘s own blog (!), “Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year” ($ub. req’d, abstract below).
Scientists know the Antarctic ice sheet is losing mass “100 years ahead of schedule.”
It is really only the warming of the West Antarctic Ice Sheet that you should worry about (at least for this century) because it’s going to disintegrate long before the East Antarctic Ice Sheet does—since WAIS appears to be melting from underneath (i.e. the water is warming, too), and since, as I wrote in the “high water” part of my book, the WAIS is inherently less stable:
Perhaps the most important, and worrisome, fact about the WAIS is that it is fundamentally far less stable than the Greenland ice sheet because most of it is grounded far below sea level. The WAIS rests on bedrock as deep as two kilometers underwater. One 2004 NASA-led study found that most of the glaciers they were studying “flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates, providing exit routes for ice from further inland if ice-sheet collapse is under way.” A 2002 study in Science examined the underwater grounding lines-the points where the ice starts floating. Using satellites, the researchers determined that “bottom melt rates experienced by large outlet glaciers near their grounding lines are far higher than generally assumed.” And that melt rate is positively correlated with ocean temperature.
The warmer it gets, the more unstable WAIS outlet glaciers will become. Since so much of the ice sheet is grounded underwater, rising sea levels may have the effect of lifting the sheets, allowing more-and increasingly warmer-water underneath it, leading to further bottom melting, more ice shelf disintegration, accelerated glacial flow, and further sea level rise, and so on and on, another vicious cycle. The combination of global warming and accelerating sea level rise from Greenland could be the trigger for catastrophic collapse in the WAIS (see, for instance, here).
You can read every thing a layman could possibly want to know about what the study does and doesn’t show at RealClimate here. Andy Revkin blogs on the NYT coverage of the study with expert commentary here.
It bears repeating that this was not the only research presented at the AGU meeting to find that warming extends beyond the Antarctic’s Peninsula region. David Bromwich of the Byrd Polar Research Centre at Ohio State also presented his new study, “Surface and Mid-tropospheric Climate Change in Antarctica,” which found:
It is found that the statistically significant Antarctic Peninsula near-surface warming on an annual basis has spread into West Antarctica reaching as far as east as the Pine Island Bay-Thwaites Glacier region.
The warming is most marked in recent years with 2007 being the warmest year in the 1960- 2007 interval ... . The warming over West Antarctica is maximized in the spring (SON) and in that season statistically significant warming stretches across all of West Antarctica and into northern Victoria Land. Weak near- surface warming is found over East Antarctica and the continent as a whole on an annual basis although continental warming in the spring is statistically significant and driven largely by the strong and widespread changes in West Antarctica.
Here is the abstract of the new Nature study:
Assessments of Antarctic temperature change have emphasized the contrast between strong warming of the Antarctic Peninsula and slight cooling of the Antarctic continental interior in recent decades. This pattern of temperature change has been attributed to the increased strength of the circumpolar westerlies, largely in response to changes in stratospheric ozone. This picture, however, is substantially incomplete owing to the sparseness and short duration of the observations. Here we show that significant warming extends well beyond the Antarctic Peninsula to cover most of West Antarctica, an area of warming much larger than previously reported. West Antarctic warming exceeds 0.1 °C per decade over the past 50 years, and is strongest in winter and spring. Although this is partly offset by autumn cooling in East Antarctica, the continent-wide average near-surface temperature trend is positive. Simulations using a general circulation model reproduce the essential features of the spatial pattern and the long-term trend, and we suggest that neither can be attributed directly to increases in the strength of the westerlies. Instead, regional changes in atmospheric circulation and associated changes in sea surface temperature and sea ice are required to explain the enhanced warming in West Antarctica.
So notwithstanding the amateur meteorologist-deniers who sometimes comment on this blog and elsewhere about how cold it is outside right now, the whole damn planet is warming and melting—even in places that are much, much colder than anywhere in the continental United States.
This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.
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Black Wallaby Posted 2:23 pm
24 Jan 2009
SOME of the points NOT covered by Joe include increased snowfall, and the alignment of West Antarctica, particularly the Peninsular, geologically with Patagonia and the tectonic warming implications. (Non Anthropogenic) However, there is so much stuff that is not discussed, that I'll have to do it by instalments. Of course he will not entertain what geologists have to say, because they are not qualified to comment on "climate science". (Let the reader decide):
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(Instalment 1) Here is an extract from a NASA release, http://earthobservatory.nasa.gov/IOTD/view.php?id=8239 on a 26-year satellite survey, which was last updated about 3 months ago (my bold emphasis added thrice):
The map is based on thermal infrared (heat) observations made by a series of National Oceanic and Atmospheric Administration satellite sensors. Because the satellite is observing energy radiated from the Earth's surface, the image shows trends in skin temperatures--temperatures from roughly the top millimeter of the land, sea ice, or sea surface--not air temperatures. Making a long-term record out of data from different sensors is challenging because each sensor has its own quirks and may measure temperatures a bit differently. None of the sensors were in orbit at the same time, so scientists could not compare simultaneous observations from different sensors to make sure each was recording temperatures exactly the same. Instead, the team checked the satellite records against ground-based weather station data to inter-calibrate them and make the 26-year satellite record. The scientists estimate the level of uncertainty in the measurements is between 2-3 degrees Celsius.
For those of you who would like to see typically what Joe does not include, I urge you to study the full release, and to take special notice of the following image link: http://earthobservatory.nasa.gov/IOTD/view.php?id=6502
This image has much relevance to my next post.
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A couple of quick interim notes on Joe's referenced 50-year survey article in Nature:
a) One of the authors is Michael E. Mann, the inventor of the discredited Hockey-stick graph which "cancelled" the well established MWP and LIA. That authorship alone, should compel rationalists to look more carefully at other evidence that is out there!!!
b) An AFP report on the paper @
http://www.google.com/hostednews/afp/article/ALeqM5i2WPmF ... includes the following statement:
The work is based on a 25-year archive of observations by satellites measuring the intensity of infrared light radiated by the snow pack. These were buttressed by data from automated weather stations deployed around the Antarctic coast since 1957.
(more on a 35-year ground-instrument survey later)
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Black Wallaby Posted 11:26 am
25 Jan 2009
http://earthobservatory.nasa.gov/IOTD/view.php?id=6502
Notice two things; a) Pronounced warming of the waters and land around the Peninsular and West Antarctica, and b) The Peninsular is the northernmost part of the continent.
Another map in part 3 below will show a geographical similarity between the Peninsular and Patagonia, (the southern end of the Andes), and close proximity and alignment between them.
There is a later version of the NASA graph: http://earthobservatory.nasa.gov/IOTD/view.php?id=8239 ,1981 - 2007 in which the temperature variation is less stark, but there are caveats, which should be considered. (See Part 1 above)
This is a lead-up to some work by geologists, including assessment of tectonic activity, rifting, and volcanoes, that may explain some of the differences between East and West/Peninsular. Clearly, this would have no connection with AGW. The second citation also implies that what we are seeing recently is nothing unusual:
"Crustal Motions of the Bedrock of the West Antarctica" (Lots of volcanoes there etc)
http://www.ig.utexas.edu/outreach/polar/pepperoni/pdfdocs ...
Here is an extract from: http://sp.lyellcollection.org/cgi/content/abstract/202/1/ ... that might be of interest.
... "Second, the present-day WAIS appears to be in a near maximum configuration that has existed at several times since 9 Ma but was rarely exceeded..."
Study of both papers in full is recommended.
There is more; a step at a time!
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Black Wallaby Posted 11:58 am
27 Jan 2009
http://www.antarctica.ac.uk/met/gjma/ If you click on the third penguin icon down, it opens an interesting map, showing 11 stations in East Antarctica, and 4 on or near The Peninsular. (It also shows the southern tip of Patagonia which is of geological significance, as discussed in Part 2, above.)
Unfortunately, the statistical uncertainty is expressed differently to the 50-year study raised by Joe, but put simply, the stronger the colour in the vertical bars, the higher the confidence level. From this it can be seen that the trend in East Antarctica is rather flat, although the confidence levels are not high. On the other hand the warming trend is strong in the Peninsular, with high confidence levels.
Here is part of the abstract quoted by Joe, including his bold emphasis:
Here we show that significant warming extends well beyond the Antarctic Peninsula to cover most of West Antarctica, an area of warming much larger than previously reported. West Antarctic warming exceeds 0.1 °C per decade over the past 50 years, and is strongest in winter and spring. Although this is partly offset by autumn cooling in East Antarctica, the continent-wide average near-surface temperature trend is positive. Simulations using a general circulation model reproduce the essential features of the spatial pattern and the long-term trend, and we suggest that neither can be attributed directly to increases in the strength of the westerlies. Instead, regional changes in atmospheric circulation and associated changes in sea surface temperature and sea ice are required to explain the enhanced warming in West Antarctica.
And here is an extract from a NASA release http://earthobservatory.nasa.gov/IOTD/view.php?id=8239 that discusses the same 26 year satellite record which was calibrated and extrapolated to 50 years, using surface station measured air temperatures (my bold emphasis added):
Making a long-term record out of data from different sensors is challenging because each sensor has its own quirks and may measure temperatures a bit differently. None of the sensors were in orbit at the same time, so scientists could not compare simultaneous observations from different sensors to make sure each was recording temperatures exactly the same. Instead, the team checked the satellite records against ground-based weather station data to inter-calibrate them and make the 26-year satellite record. The scientists estimate the level of uncertainty in the measurements is between 2-3 degrees Celsius.
Here are some observations on the above:
1] The 50-year study (Mann et al) declares: "the continent-wide average near-surface temperature trend is positive". This implies that East Antarctica is warming, (on which much has been trumpeted elsewhere), but the magnitude is not given. (Uh?)
2] The 50-year study declares that West Antarctica warming exceeds 0.1 degree C per decade, but the NASA quote referring to calibration of satellite infra-red surface radiation to near surface air temperature gives that"a level of uncertainty in the measurements is between 2-3 degrees Celsius" Hmmmmm!
3] The 50-year study declares: "changes in sea surface temperature and sea ice are required to explain the enhanced warming in West Antarctica"
a] Part 2 above shows that there is tectonic activity around West Antarctica, but of course this is in the field of geology, not "climate science".
b] Other information shows a net increase in sea-ice area for the whole of Antarctica.
4] The 50-year study declares: "Here we show that significant warming extends well beyond the Antarctic Peninsula to cover most of West Antarctica, an area of warming much larger than previously reported." Well actually this has been known since at least 2004 and was certainly published by NASA in April 2006; e.g. http://earthobservatory.nasa.gov/IOTD/view.php?id=6502
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