Global climate picture grows sharper, worse

Saturday, August 19, 2006 Minneapolis-St. Paul Star Tribune: There have been exceptions, but generally speaking the outlook on global warming grows more dire with each addition of scientific detail. So it was last week, with one new report showing that the Greenland ice sheet is melting much more rapidly than was previously thought, and another concluding that shrinkage of the Antarctic ice is not being offset by heavier snowfall, as some climate experts had hoped. Loss of ice in these two vast masses is closely watched for several reasons, foremost being the rise in sea level worldwide. As has often been noted, a complete meltdown of just the Greenland ice would lift the ocean surface by some 20 feet. That's a remote possibility, of course, but even slow retreat can mean big changes. Measurements made between 1997 and 2003 suggested Greenland was losing about 19 cubic miles of ice each year, on average. The annual rise in sea level was then estimated to be about one-tenth of an inch, with Greenland contributing about 20 percent. Greening of Greenland Last spring, scientists at NASA surmised that the melt was occurring at twice that rate. Some glaciologists thought those figures were too high, but research reported last week in the journal Science found they were conservative. Satellite data suggest Greenland is losing 57 cubic miles of ice per year, three times the earlier estimate. At the other end of the Earth, the news is also discouraging. Climate experts have conjectured that some of the water flowing from the Antarctic ice sheet might return as snow, slowing the rate of loss. But new figures show that snowfall there hasn't changed much in the last half century. Taken together, the new figures suggest that world sea levels might rise roughly three feet by the end of the century, more than enough to flood low-lying areas. Much sooner than that, scientists warn, cold water flowing off Greenland could disrupt the ocean currents that convey heat from the tropics into the north Atlantic, moderating European winters. The usual naysayers were quick to note that the new Greenland calculations are based on only 30 months of satellite data; in the weeks ahead, some will no doubt argue that the new studies only prove their contrarian point that climate research in general is inconclusive, contradictory and quick to change.