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quote:Originally posted by ukmicky(snip)1.Could the lower regions of the glaciers be comprised of a form of ice which is weak and can't handle the mass of the glacier above it, giving way and causing the glacier to slip. Are there different types of ice with diferent stengths and properties2Or if the glaciers got to big and heavy can their own weight and stored up energy due to then being on a slope cause the bottom region of the glacier to heat up and melt lubricating and speeding up there natural movement towards the sea.3Are their any volcano's under greenland which could cause the ice to melt or does greenland suffer from minor earthquakesMichael
quote:Originally posted by VAlibrarianIf I am a crackpot, I am not of the anti-nuke variety. On the contrary, most of those who seriously consider human activities responsible for the observed rise in temperature are very much in favor of nuclear power. Nuclear power produces no CO2. If we wish to address the atmospheric CO2 problem (those of us who consider it a problem)it is obvious that we have to get energy from somewhere or no longer have cooked dinners. As I much prefer cooked meat to the raw stuff, but am quite convinced that our CO2 contributions to the atmosphere will come back to haunt our grandkids, I have no choice but to favor the expansion of nuclear power to take up the slack that would result from reducing use of coal and petroleum.
quote:Originally posted by VAlibrarianMy belief is that public opinion will gradually catch up to the 99% of atmospheric scientists who share my view. Yours is that the scientists will eventually catch up to the general public. Could be, but how often does that happen?
quote:Originally posted by VAlibrarianThere are several professors of environmental studies or atmospheric science (Patrick Michaels of the University of Virginia and Richard Lindzey of MIT) who argue that the majority view is exaggerated. At first some of these argued that global temperatures are not climbing. They no longer can convincingly make that argument now, so they argue in some cases that it is not yet proved to be related to human activities. The two scientists mentioned in this paragraph have taken lucrative public speaking fees from oil and electric utility companies.
quote:Over the past couple years, certain industries have left this group, because they have decided that global warming is real and is caused by fuel burning and that they can no longer pretend it is not. BP will tell you that its acronym no longer stands for "British Petroleum", but rather "Beyond Petroleum". In fact, in the United States some industries like General Electric are ready to make a profit from exploring renewable energy, while Exxon and General Motors are clinging to the concept of "when you run out of gas, drill deeper".
quote:Academia is not monolithically solid in favor of global warming, but there is a definite majority.
quote:However, the strong scientific support for man-made global warming implies that such alternative opinions are not widely held. In the journal Science, an essay by Naomi Oreskes considered the abstracts of all 928 scientific articles in the ISI citation database identified with the keyword "global climate change". Dr. Oreskes concluded that none of these abstracts attempt to refute the position that man-made emissions of greenhouse gases are a substantial contributor to recent warming.
quote:>1 Are there different types of ice with diferent stengths and propertiesThere certainly are but I don't really know of any reason to think the mixtures vary so you could suddenly get ice that is on average weaker at the bottom.
quote:Originally posted by crandlesI just don't know about whether dust and dirt at the bottom could cause weakness. However I would question the relevance:Dust and dirt from the last 150 years would be on top of the glacier. This will make it easier to melt the top by reducing the albedo and also the melting point. However, I am not sure how much effect this has.Since we are seeing glaciers retreat in large numbers of diverse locations (~98% of glaciers, I think), it would be very odd if it could be put down to local factors eg volcanoes.I am not sure why you would expect a difference at the bottom eg comparing ice that formed 10,000 years ago with ice from 10,100 years ago.
quote:Originally posted by another_someoneI am not at all sure that anyone knows what percentage of ice is melting, since like so much else regarding climate, there are so many different ways of measuring it, and so much of it that still is not measured.
quote:Impact on glaciers Global glacial mass balance in the last fifty years, reported to the WGMS and the NSIDC. The increased downward trend in the late 1980s is symptomatic of the increased rate and number of retreating glaciers.Global warming has led to negative glacier mass balance, causing glacier retreat around the world. Oerlemans (2005) showed a net decline in 142 of the 144 mountain glaciers with records from 1900 to 1980. Since 1980 global glacier retreat has increased significantly. Similarly, Dyurgerov and Meier (2005) averaged glacier data across large scale regions (e.g. Europe) and found that every region had a net decline from 1960 to 2002, though a few local regions (e.g. Scandinavia) have shown increases. Some glaciers that are in disequilibrium with present climate have already disappeared  and increasing temperatures are expected to cause continued retreat in the majority of alpine glaciers around the world. Upwards of 90% of glaciers reported to the World Glacier Monitoring Service have retreated since 1995 .
quote:Originally posted by crandlesI guess that 98% of glaciers retreating that I quoted was from Oerlemans (2005)'s 142 of 144. The percentage of ice is a rather different thing to percentage of glaciers retreating. However, why do you think a sample selection (if done using an appropriate random selection technique) is not going to give a good representation of the population?
quote:Originally posted by crandlesSure those variation are possible and if your random sample was just randomly selected from all the sites with adequately long records that could be an issue. Such an issue would be difficult to solve if your sample size was just 50. If the sample size is much larger though you can split it in two according to how easily accessable the different sites are. If the 2 subsamples show differing trends then a more sophisticated regionalised sample technique is needed. The remoter sample items are given appropriate weight to represent all the remote glaciers in the region. A similar splitting of the sample can be done based on length of record available.If the real figure for retreating glaciers was less than 90% then it would be odd for an appropriate random selection technique using an appropriatly large sample size arrived at an over 98% figure. A larger discrepancy may be possible if an inappropriate sample technique had been used. However, I don't see that you have made any reference to the techniques used and why they are inappropriate yet. Until you do that, I won't think the 98% figure is perfect but I won't think it is far out either.