Volume 7, Number 12: 24 March 2004
Invoking the canary in the coal mine concept with respect to the premise that "Earth's climate is changing rapidly," Albert (2004) says "the harbingers of change can be seen vividly in the polar regions," where "ice cover is melting, ice shelves ... are crumbling, and glaciers ... are disappearing." In contrast to these largely localized observations, studies that focus on climate change throughout the bulk of the Arctic and Antarctic have found something far different, i.e., significant cooling over the last several decades [see, for example, our Editorials of 10 Mar 2004 and 17 Mar 2004]. Consequently, if the climatic behavior of earth's polar regions over the latter half of the 20th century is truly a harbinger of things to come for the rest of the world, we would appear to have little to fear from the continued burning of fossil fuels and the CO2 thereby released to the atmosphere, as these supposedly highly-sensitive regions of the globe are definitely not experiencing widespread warming.
What happens in some parts of earth's polar regions, however, may be more important than what happens in others. In the Arctic, for example, if Greenland were to experience a sustained dramatic warming that eventually led to the melting of its entire ice sheet, sea levels could rise by some five to six meters globally (Mercer, 1978; Cuffey and Marshall, 2000). Hence, it behooves us to consider this particular part of the Arctic in more detail, which is exactly what Chylek et al. (2004) did. So what did they find?
Looking first at three coastal stations in southern and central Greenland that possess almost uninterrupted temperature records between 1950 and 2000, Chylek et al. discovered that "summer temperatures, which are most relevant to Greenland ice sheet melting rates, do not show any persistent increase during the last fifty years." In fact, working with the two stations with the longest records (both over a century in length), they determined that coastal Greenland's peak temperatures occurred between 1930 and 1940, and that the subsequent decrease in temperature was so substantial and sustained that current coastal temperatures "are about 1°C below their 1940 values." Furthermore, they note that "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." Hence, as with the Arctic as a whole, Greenland has not experienced any net warming over the most dramatic period of atmospheric CO2 increase on record. In fact, it has cooled during this period ... and cooled significantly.
At the start of the 20th century, however, Greenland was warming, as it emerged, along with the rest of the world, from the depths of the Little Ice Age. What is more, between 1920 and 1930, when the atmosphere's CO2 concentration rose by a mere 3 to 4 ppm, there was a phenomenal warming at all five coastal locations for which contemporary temperature records are available. In fact, in the words of Chylek et al., "average annual temperature rose between 2 and 4°C [and by as much as 6°C in the winter] in less than ten years." And this warming, as they note, "is also seen in the 18O/16O record of the Summit ice core (Steig et al., 1994; Stuiver et al., 1995; White et al., 1997)."
In commenting on this dramatic temperature rise, which they call the great Greenland warming of the 1920s, Chylek et al. correctly conclude that "since there was no significant increase in the atmospheric greenhouse gas concentration during that time, the Greenland warming of the 1920s demonstrates that a large and rapid temperature increase can occur over Greenland, and perhaps in other regions of the Arctic, due to internal climate variability such as the NAM/NAO [Northern Annular Mode/North Atlantic Oscillation], without a significant anthropogenic influence." These facts thus lead them to speculate that "the NAO may play a crucial role in determining local Greenland climate during the 21st century, resulting in a local climate that may defy the global climate change."
In conclusion, the study of Chylek et al. clearly demonstrates that the entire history of anthropogenic CO2 emissions since the inception of the Industrial Revolution has had no discernable impact on Greenland air temperatures, while the studies described in our Editorials of 10 Mar 2004 and 17 Mar 2004 demonstrate pretty much the same thing for the entire Arctic and Antarctic regions of the globe. Hence, there is absolutely no substance to the climate-alarmist claim that earth's polar regions are providing evidence for an impending CO2-induced warming of any magnitude anywhere.
| Sherwood, Keith and Craig Idso |
References
Albert, M.R. 2004. The International Polar Year. Science 303: 1437.
Chylek, P., Box, J.E. and Lesins, G. 2004. Global warming and the Greenland ice sheet. Climatic Change 63: 201-221.
Cuffey, K.M. and Marshall, S.J. 2000. Substantial contribution to sea-level rise during the last interglacial from the Greenland ice sheet. Nature 404: 591-594.
Mercer, J.H. 1978. West Antarctic ice sheet and CO2 greenhouse effect: A threat of disaster. Nature 271: 321-325.
Steig, E.J., Grootes, P.M. and Stuiver, M. 1994. Seasonal precipitation timing and ice core records. Science 266: 1885-1886.
Stuiver, M., Grootes, P.M. and Braziunas, T.F. 1995. The GISP2 18O climate record of the past 16,500 years and the role of the sun, ocean and volcanoes. Quaternary Research 44: 341-354.
White, J.W.C., Barlow, L.K., Fisher, D., Grootes, P.M., Jouzel, J., Johnsen, S.J., Stuiver, M. and Clausen, H.B. 1997. The climate signal in the stable isotopes of snow from Summit, Greenland: Results of comparisons with modern climate observations. Journal of Geophysical Research 102: 26,425-26,439.