March 15, 2004

Greenland’s Secret

Filed under: Arctic, Glaciers/Sea Ice, Polar

The recent hype in Nature notwithstanding, Greenland has been cooling for the better part of two generations.

It’s hot news: Temperatures in Greenland have been rising like a rocket during the past 10 years or so—returning to the temperatures that characterized the 1930s, ’40s, and ’50s.

Yet that bit of history—that temperatures were as warm or warmer in Greenland 50 years ago—appears lost on the global warming crowd. Instead, they have increasingly pointed a finger at the changing conditions there during the past decade as a clear sign of anthropogenic global warming.

An article in the March 11, 2004, issue of Nature magazine even goes so far as to suggest that Greenland may be on a path of warming and ice loss from which it can never recover. Apparently, Nature writer Quinn Schiermeier is ignorant of the fact that 70 years ago, a similar temperature rise in Greenland was followed by six decades of cooling—it seems as if it recovered from that warming just fine!

A refresher course on Greenland’s climatic history—one that somehow escaped the attention of Schiermeier and his ilk—appears in the March issue of Climate Change. The article, entitled Global Warming and the Greenland Ice Sheet, is by a group of scientists from the United States and Canada. Remarkably, the journal editor is Stanford’s Stephen Schneider, who is widely recognized as one of the leading greenhouse firebrands alive today. The article’s title certainly leads a reader to believe that we are about to hear another story on warming in Greenland causing potentially devastating melting of the ice and sea level rise and so on and so on.

But global warmers had better sit down and take a deep breath of CO2-enriched air before reading the second, third, and fourth sentences of Chylek et al.’s abstract:

Since 1940, however, the Greenland coastal stations data have undergone predominantly a cooling trend. At the summit of the Greenland ice sheet, the summer average temperature has decreased at the rate of 2.2°C per decade since the beginning of the measurements in 1987. This suggests that the Greenland ice sheet and coastal regions are not following the current global warming trend.

Greenland clearly hasn’t read its press. How many times have we heard that warming in Greenland is causing ice to melt, sea level to rise, ocean circulations to changes, and general climate calamity to proliferate? The Chylek et al. team reveals that from 1940 to 2000, annual temperatures in Godthab have cooled by 1.8°C, Angmagssalik has cooled by 1.6°C, and Egedesminde has cooled by 1.2°C from 1950–2000.

Not that there hasn’t been any warming. On the contrary, the authors found warming, all right:

…in the 1920s when the average annual surface air temperature rose between 2°C and 4°C in less than 10 years…at a time when the change in anthropogenic production of greenhouse gases was well below the current level.

The busy beavers here at World Climate Report downloaded the temperature data for Greenland available from the United Nations Intergovernmental Panel on Climate Change (IPCC). These data are provided as monthly temperature anomalies (departures from normal) for the 30 5°-latitude by 5°-longitude grid boxes covering Greenland over the period January 1940–November 2003. Figure 1 shows the IPCC near-surface air temperature record for Greenland, which includes a highly statistically significant cooling of 0.11°C (0.20°F) per decade over the past 64 years!

IPCC Temperatures

Figure 1. IPCC temperature anomalies (°C) available for Greenland from January 1940 to November 2003.

For a little geographic tour, we’ve also included three individual records. Angmagssalik, on the southeast coast, shows around six decades of cooling, ending around 1990, and one really warm year: 2003. No one ever passed a doctoral exam in climate science who gets excited about one year that bucks a trend.

Station Temperatures

Figure 2. Annual average temperatures at three locations: Southeastern Greenland, Southwestern Greenland, and Baffin Island (across from Northwestern Greenland).

That trend isn’t evident at Greenland’s bustling capital, Godthab (Nuuk), on the southwest coast. Our search for a northern station with comparable temperature data led us to Clyde, just across the Davis Strait on Baffin Island. Same story: No story.

Many of the warmest monthly anomalies in the Greenland temperature record occurred prior to 1950 and well before the largest increases in greenhouse gas concentrations. Variations in the data are strongly linked to an atmospheric circulation flip-flop known as the North Atlantic Oscillation (NAO)—and not to any global temperature increase.

And now to the burning question: Has Greenland’s ice mass been declining (as suggested repeatedly by the greenhouse crusade), increasing, or remaining unchanged? A 1°C warming of the coastal stations would cause an increase in the melt area of 73,000 square kilometers, as the researchers note. Given the 1°C to nearly 2°C cooling found in the coastal stations, prompts Chylek et al. to conservatively state, “The results are inconclusive for the ice sheet as a whole, owing to the large uncertainties when balancing very large, difficult to measure, offsetting quantities.”

“Even the direction in which the mass of the Greenland ice sheet is currently changing is in dispute,” they add. In other words, anyone claiming that Greenland is melting is certainly not well supported in the scientific literature.

Global warmers who gleefully watch film clips from the upcoming movie The Day After Tomorrow may counter that the cooling in Greenland is a signal that the thermohaline ocean circulation is indeed changing and the catastrophic sudden cooling (caused ironically by global warming) is closer than the standard 10 years away. But all the cooling took place from 1940 to the early 1980s, as Figure 1 shows. Since that time, Greenland has been rebounding, but has not yet achieved the high temperatures of the 1940s. There is no evidence of any accelerated cooling in recent years that could signal the end of the Gulf Stream and the beginning of freezing temperatures in North America and Europe.

Had Chylek et al. reported warming in Greenland of 1°C to 2°C over the past half-century, the article would have been front page news the world over. But they showed cooling in Greenland (and lots of it), a finding completely consistent with IPCC data. Greenland is obviously having a little trouble warming up to the numerical model predictions for substantial rise in temperatures given the ongoing buildup of greenhouse gases.

We appreciate the work of Chylek et al. and the honesty shown by editor Stephen Schneider to share Greenland’s best kept secret. But, you could have read it here almost four years ago, when we published a slew of Greenland temperature data in World Climate Report on August 14, 2000 (http://www.co2andclimate.org/climate/previous_issues/vol5/v5n22/index522.htm), in response to a Science magazine article that was profoundly misleading—just like last week’s Nature piece of work.

References:
Chylek, P., J.E. Box, and G. Lesins, 2004. Global Warming and the Greenland Ice Sheet. Climatic Change, 63, 201–221.

Schiermeier, Q., 2004. A Rising Tide. Nature, 428, 114–115.

Krabill, W., et al., 2000. Greenland ice sheet: High elevation balance and peripheral thinning. Science, 289, 428–430.




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