Is Greenland really melting?
“Greenland is melting! Greenland is melting!” cried Chicken Little in a spate of press stories based on two articles in Science magazine. Apparently, C.L. hasn’t yet learned to read, count, or get on the Internet: three elementary skills that would have replaced his faulty chickenvision with A-plus accuracy.
The first paper is by veteran glaciologist William Krabill, whose earlier laser-based studies of the West Greenland Ice Sheet—by far the largest chunk of land-ice in the Northern Hemisphere—showed an actual thickening of up to seven feet in the 1980s. That fact may seem counterintuitive to someone like C.L., but people who understand global warming suggest Greenland’s ice indeed might thicken, especially if the warming occurs mostly in winter. Warming the air from its current -50°F to, say, -40°F, is likely to increase snowfall, since “warmer” air is generally moister and precipitates more water.
In his latest study, Krabill and nine coauthors examine the very brief period 1994-1999. In combination with another study published last year, they find the largest mass--the ice that’s higher than 6,500 feet above sea level--is “rising” at the rate of 0.2 ± 0.2 inches per year. But the land is rising, too--at about 0.15 inches per year. That leaves, in Krabill’s estimation, +0.04 ± 0.2 inches per year for this massive ice cap, which encompasses the vast majority of Greenland. In the far northern island’s coastal regions, ice retreat predominates over about 70 percent of the area studied.
In a companion paper in the same issue of Science, Thomas and colleagues write that “The [whole] region has been in balance, but with thickening of 21 centimeters per year [8.3 inches] in the southwest and thinning of 30 centimeters per year [11.8 inches] in the southeast.”
C.L.’s squawking appears to have been syndicated: We can’t count the number of press reports blaming the situation on global warming. Alas, his inability to search the Internet or even read a graph precluded his answering this obvious question: How much has it warmed in southeastern Greenland?
C.L. can’t answer, but we can. We hereby present the best (longest-running and without gap) temperature record from southeastern Greenland, from Angmagssalik (latitude 65.6°N, longitude 37.6°W, or about 2,700 miles northeast of Washington, DC). For 70 years now, a cooling trend has persisted.
What about for Nuuk in southwestern Greenland (64.2°N, 51.8°W, a mere 2,200 miles from DC)? The ice in that region is thickening, and cooling has continued for 70 years also. It seems the ice either accretes or ablates pretty much independent of temperature.
Yet Krabill and colleagues attempted to relate the melt in the southeast to the temperatures of 1994-1999, the period we have circled in the Angmagssalik record. They compared temperature anomalies for those years with the average temperature beginning in 1979.
For what it’s worth, the annual average temperature at Angmagssalik, based upon the entire 105-year record, is around -1.28ºC. The average 1994-1999 temperature of about -1.08ºC is pretty close to normal. It’s about one degree lower than the 1930-1950 temperatures (before human activity changed the greenhouse effect very much). But the period 1979-1999, which Krabill used for averaging, is actually a little colder than the record’s last five years, so the 1994-1999 temperatures appear “warm.” Just throw out the first 85 years of this excellent temperature history to come to that false conclusion!
So, under the simplified logic that warmer means more melting, Krabill then calculated the temperature change must have been responsible for 0.4 inches of the total sea level rise of the 20th century that the United Nations Intergovernmental Panel on Climate Change (IPCC) noted in its 1996 report.
Huh? Did someone say 1996? But Krabill’s study covers 1994 through 1999, and the melting is taking place where it is has been cooling for three-quarters of a century! C.L. was too chickenheaded to think this through, but here’s how Krabill and company worked their way around this slight nunatak:
Greenland temperature records from 1900-95 show highest summer temperatures in the 1930s, followed by a steady decline until the early 1970s and a slow increase since. The 1980s and 1990s were about half a degree colder than the 96-year mean. Consequently, if present-day thinning is attributable to warmer temperatures, thinning must have been even higher earlier this century.
How interesting. So the “natural” (pre-greenhouse) rate of melting in southern Greenland was higher than it is today. And overall, the largest portion of the ice is at best neutral, as Thomas’s companion article makes clear: “On average, the region has been in balance” in recent decades.
What all of that means is that Greenland will have to show a pretty massive melt rate to even equal how much water it lost before there was a CO2-producing car in every U.S. garage. And in any event, don’t look for it to melt away very fast.
No doubt with Chicken Little’s help, Reuters reported: “If all of the ice sheet melted, it would raise world sea level by seven yards.”
“This thinning,” Krabill told Reuters, “is a clear indication the global climate is warming up.” That’s a bit of a stretch. As the graph shows, during the time the ice is growing and in the places where it is receding, it has been cooling for seven decades!
So how long do we have left to live? If the ice cap lost 0.15 inches per year--the lowest limit given in Krabill’s broad range--it would take about 800,000 years to melt. Between then and now, if history is any guide, we’re likely to experience two or three major ice ages, and we will have run out of fossil fuels about 798,000 years before then.
Sorry, C.L., looks like Greenland’s here to stay!
According to Nature magazine, University of Virginia environmental sciences professor Patrick J. Michaels is probably the nation’s most popular lecturer on the subject of climate change. Michaels is coauthor of The Satanic Gases: Clearing the Air About Global Warming.
Krabill, W., et al., 2000. Greenland Ice Sheet: High Elevation Balance and Peripheral Thinning. Science, 289, 428-430.
Thomas, R., et al., 2000. Mass Balance of the Greenland Ice Sheet at High Elevations. Science, 289, 428-430.