Climate alarmists contend that global warming is amplified at high northern latitudes, and that high-latitude permafrost is degrading ever more rapidly with the passage of time. Are they right?
In a study germane to this question, Jorgenson et al. (2001) examined the extent, history and rates of permafrost degradation in the Tanana River valley lowlands of central Alaska over the past 300 years, using a combination of methods that included repeat aerial photography (1949, 1978 and 1998), radiocarbon dating of organic material, and tree ring analyses. As they describe it, the evidence they collected indicates that "nearly all the permafrost degradation has occurred since 1750 and that 83% of the degradation occurred before 1949." These observations imply that only 17% of the 250-year period's total permafrost meltdown occurred during the final 50-year period (1950-2000), which comprises the final 25% of the entire period of permafrost thawing and should thus have been expected to provide something in excess of 25% of the total meltdown, since the air's CO2 content rose the fastest of all during this latter period, which is claimed by the world's climate alarmists to have been host to a warming that was "unprecedented" compared to all other warming periods of the prior one to two millennia. Consequently, rather than demonstrating an acceleration of permafrost degradation over this critical period of time, these real-world data suggest just the opposite, as permafrost degradation throughout this part of Alaska appears to have actually slowed during the last half of the 20th century.
One year later, Romanovsky et al. (2002) presented a 1924-2001 history of mean annual temperatures for Barrow, Alaska, at soil depths of 0.08 m (the "active layer"), 0.5 m, and 1.0 m (about 60 cm below the permafrost table). This work revealed, in their words, that permafrost temperatures were "very similar during the 1940s and 1990s (except for unprecedented warm extremes of 1998 and 1999)." However, even including these "unprecedented warm extremes," we calculate from their Figure 3 that the mean temperature about 60 cm into the permafrost (-9.15°C) -- over what climate alarmists often refer to as the warmest period of the past millennium, i.e., 1990 and onward -- was no warmer than, or possibly even cooler than, the temperature of the 16-year period 1937-1952 (-9.06°C).
Consequently, and in spite of all of the hype about dramatic late 20th-century warming in the permafrost regions of Alaska, real-world data demonstrate that it was no warmer at Barrow at the dawn of the 21st century than it was some 48 to 63 years earlier, and that the area's permafrost is thus in no more danger of being wiped out any time soon than it was in the days of our great-grandparents. In addition, the five scientists inform us that degradation of permafrost does not proceed as rapidly as many climate alarmists claim it does. As Romanovsky et al. describe it, "degradation of permafrost is a slow process," and "if recent trends continue, it will take several centuries to millennia [our italics] for permafrost in the present discontinuous zone to disappear completely in the areas where it is actively warming and thawing."
In another pertinent study, Osterkamp (2007a) reviewed what is known about the evolution of climate and permafrost in Alaska over the past three decades. He first reports that "permafrost warmed at most sites north of the Brooks Range from the Chukchi Sea to the Alaska-Canada border, south along a transect from Prudhoe Bay to Gulkana and at sites up to 300 km from the transect," noting that "the warming was coincident with the statewide warming of air temperatures that began in 1976/1977," the magnitude of which "was 3 to 4°C for the Arctic Coastal Plain, 1 to 2°C for the Brooks Range including its northern and southern foothills, and 0.3 to 1°C south of the Yukon River." However, this warming, in his words, "was seasonal (primarily in winter) with little change in summer conditions." Consequently, he found that permafrost "active layer thicknesses did not [our italics] increase and were not [our italics] correlated with warming permafrost conditions."
In a contemporaneous paper, Osterkamp (2007b) reviewed the role played by snow cover in "the warming of permafrost in Alaska during the twentieth century," finding that for Barrow, for the period 1977-1998, "about one half of the permafrost warming for that period was a result of increased air temperatures while the other half [was] attributable to increased snow cover thicknesses (Stieglitz et al., 2003)." In addition, for Healy in interior Alaska, he notes that "the 1990s was a period of increased snow depths, and that snow cover effects during this period "were almost entirely responsible for warming and thawing permafrost at Healy," while noting that similar snow conditions during this period were observed "throughout Alaska."
In discussing his findings, the University of Alaska researcher says "there is a perception that climatic warming was the cause of the twentieth-century global warming and thawing of permafrost and associated terrain instability," citing Gore (2006). However, he notes that "published results do not support this viewpoint," citing Zhang et al. (2001) and Osterkamp (2007a). Consequently, after presenting the data from Healy described in his report, which appear to be characteristic of much of the state, Osterkamp concludes that "snow cover has played a significant role in it," ranging from being responsible for "about one half" of the recent permafrost thawing to being "almost entirely responsible" for it.
In concluding this summary, we note that: (1) although it indeed warmed in Alaska over the latter part of the 20th century, most of that warming occurred in the winter, when it had little impact on permafrost, (2) the warming only returned permafrost temperatures back to what they had been in the late 1930s, the 1940s, and the early 1950s, which also implies little enhancement of permafrost degradation over the past several decades, and (3) late 20th-century permafrost degradation may well have been due more to increased snow depth than to regional warming. As a result, climate-alarmist claims of a recent significant acceleration of permafrost degradation in response to global warming are pretty much refuted by these real-world observations.
Gore, A. 2006. An Inconvenient Truth. Rodale Press, New York, New York, USA.
Jorgenson, M.T., Racine, C.H., Walters, J.C. and Osterkamp, T.E. 2001. Permafrost degradation and ecological changes associated with a warming climate in central Alaska. Climatic Change 48: 551-579.
Osterkamp, T.E. 2007a. Characteristics of the recent warming of permafrost in Alaska. Journal of Geophysical Research 112: 10.1029/2006JF000578.
Osterkamp, T.E. 2007b. Causes of warming and thawing permafrost in Alaska. EOS, Transactions, American Geophysical Union 88: 522-523.
Romanovsky, V., Burgess, M., Smith, S., Yoshikawa, K. and Brown, J. 2002. Permafrost temperature records: Indicators of climate change. EOS, Transactions, American Geophysical Union 83: 589, 593-594.
Stieglitz, M., Dery, S.J., Romanovsky, V.E. and Osterkamp, T.E. 2003. The role of snow cover in the warming of Arctic permafrost. Geophysical Research Letters 30: 10.1029/2003GL017337.
Zhang, T., Barry, R.G., Gilichinsky, D., Bykhovets, S.S. and Sorokovifov, V.A. 2001 . An amplified signal of climatic change in soil temperatures during the last century at Irkutsk, Russia. Climatic Change 49: 41-76.Last updated 4 February 2009