The accomplished British humorous songwriters <?xml:namespace prefix = st1 ns = “urn:schemas-microsoft-com:office:smarttags” />Flanders and Swann (Donald Swann put JRR Tolkien's various Middle Earth songs to music for him) used to disparage the song 'There'll Always Be an England' by complaining, “There'll always be a North Pole, provided some damn fool doesn't go and melt it.” <?xml:namespace prefix = o ns = “urn:schemas-microsoft-com:office:office” />
Yet today it is received wisdom that we are all damn fools, because global warming is causing glaciers to melt all over the world. Most of the attention that has been paid to this phenomenon expresses concern about the effects on sea level. On top of this there is a new concern spreading through the environmentalist community about the long-term effect of glacial melt on sources of drinkable water.
However, a review of the recent scientific evidence on glaciers suggests that, as is so often the case with global warming, much of the concern is overwrought, poorly based or simply alarmist.
First and foremost, people assert we know a lot about glaciers, but we don't. We know next to nothing about glacial activity, but what we do know suggests there are as many expanding glaciers as there are shrinking ones (this even happens with two glaciers within a few miles of each other) and that there is no universal trend either way. There are more than 160,000 glaciers on the planet. Scientists have good, long-term (20-year or more) mass balance measurements on a comparative handful of them.
We are also probably years away from knowing how glaciers contribute to the recorded sea level rise of the last century. Braithwaite and Raper noted last year that “the temperature sensitivity of sea level rise depends upon the global distribution of glacier areas, the temperature sensitivity of glacier mass balance in each region, the expected change of climate in each region, and changes in glacier geometry resulting from climate change.” They concluded that “none of these are particularly well known at present,” because “glacier areas, altitudes, shape characteristics and mass balance sensitivity are still not known for many glacierized regions and ways must be found to fill gaps.” Filling in the gaps in scientific knowledge “will probably take a decade of work by many different groups in a number of disciplines.”
Another recent study looked at 67 glaciers in North America and found that glacial melting from the 50s to the 70s contributed about 0.14mm per year to sea-level rise (give or take 30 percent). More detailed measurements of 28 glaciers from the mid-1990s to 2001, when extrapolated to the rest of Alaska, yield a sea-level rise of 0.27mm per year. The authors note that these glaciers “form the largest glaciological contribution to rising sea level yet measured.” Yet even at this record rate it will take 90 years for sea level to rise 1 inch. Moreover, the authors did not take account of the Great Pacific Climate Shift that took place, as is well documented, in '76-77. The rising rate is much more likely explained by that than by global warming.
As for causes of sea level rise, Douglas and Peltier found last year that the best estimate they could come up with for the mean rate of global sea level rise over the past hundred years is “closer to 2 mm/y than 1 mm/y.” We know that the ocean heating up expands it and that glacial melting must contribute something to the rise as well, but the researchers calculate that 0.6 mm/y is probably due to thermal expansion of the oceans and only 0.3 mm/y probably comes from the melting of ice. That leaves a “puzzle” of where the extra 1 mm/y rise comes from, assuming their calculations are correct. They suggest that “several years of data and further efforts at interpretation will doubtless be required” to solve the problem.
As mentioned above, the evidence also suggests that, while many glaciers are certainly retreating quickly, this is by no means the full story. Braithwaite also last year looked at the mass balance trends in 246 glaciers worldwide from 1946 to 1995. He found that “there are several regions with highly negative mass balances in agreement with a public perception of 'the glaciers are melting,' but there are also regions with positive balances.” This holds true even within continents. In Europe, “Alpine glaciers are generally shrinking, Scandinavian glaciers are growing, and glaciers in the Caucasus are close to equilibrium for 1980-95.” Globally, adding all the results together, “there is no obvious common or global trend of increasing glacier melt in recent years.”
If the overall amount of glaciation is stable, it should therefore be apparent that there will be little or no disruption to the world's fresh water supplies engendered by the melting of glaciers. Of the world's 1.4 billion cubic kilometers of water, 2.5 percent is fresh water. Of the surface waters, 68.9 percent is locked in glaciers, 30.8 percent is groundwater and 0.3 percent is in lakes and rivers. This means that very little of the earth's water supply is easily accessible as potable water for drinking, bathing and sanitation.
Yet from the point of view of the world's need for more potable water, it might be regarded as a good thing that less freshwater be locked up in glaciers. If they are melting, whether naturally or for anthropogenic reasons, it would clearly be a good thing if we can harness the freshwater runoff to the general benefit of humanity. However, as should be clear from those figures, it is pretty unlikely that the resource is going to disappear. The scientific evidence suggests that the damn fools are not those supposedly melting the ice, but those who believe every alarmist warning that melting is a serious problem.