Volume 7, Number 30: 28 July 2004
In a study of lichens of the subspecies Rhizocarpon geographicum found on avalanche boulder tongues in the eastern part of the Massif des Ecrins of the French Alps (45°00' S, 6°30' E), Jomelli and Pech (2004) make an important discovery that adds to the growing body of evidence which demonstrates that what climate alarmists call the unprecedented and CO2-induced warming of the 20th century was neither unprecedented nor driven by rising CO2 concentrations.
According to the findings of Jomelli and Pech, high-altitude avalanche activity during the Little Ice Age (LIA) reached an early maximum prior to 1650, after which it decreased until about 1730, whereupon it increased once again, reaching what was likely its greatest maximum about 1830. In support of these findings, Jomelli and Pech note that "a greater quantity of snow mobilized by avalanches during the LIA can be supported by the fact that the two periods, AD1600-1650 and 1830, during which the run-out distances [of the avalanches] were maximum at high elevation sites, have corresponded overall to the periods of maximum glacial advances for these last 500 years (Le Roy Ladurie, 1983; Reynaud, 2001)." In addition, they report that "since 1850 most French Alpine glaciers have decreased," and that "the mass balance of these glaciers is directly correlated with summer temperature and spring precipitation (Vincent and Vallon, 1997; Vincent, 2001, 2002)."
The findings of Jomelli and Pech, plus those of the other scientists they cite, all suggest that the "beginning of the end" of the Little Ice Age started somewhere in the early to mid-1800s. Interestingly, Moore et al. (2002) determined a similar start-time for the demise of the Little Ice Age from temperature data gathered on Mount Logan in Canada, while further support for this conclusion has come from studies of still other parameters, including deep soil temperatures (Gonzalez-Rouco et al., 2003), deep ocean temperatures (Lindzen, 2002), and dates of ice break-up of lakes and rivers (Yoo and D'Odorico, 2002). What is more, this is also the period of time during which the temperature record of Esper et al. (2002) indicates that the entire Northern Hemisphere began its nearly-linear-with-time recovery from the depths of the Little Ice Age. As Briffa and Osborn (2002) describe it, Esper et al.'s record clearly shows that the warming of the 20th century was actually "a continuation of a trend that began at the start of the 19th century."
In contrast to these observations, the infamous temperature history of Mann et al. (1998, 1999) -- which is cited by climate-alarmists as justification for the ungodly warming power they attribute to anthropogenic CO2 emissions -- post-Little Ice Age warming did not begin until about 1910. Consequently, it can be appreciated that (1) perhaps half of the warming experienced by the earth in recovering from what was likely the coldest part of the Little Ice Age occurred well before the Mann et al. temperature history indicates any warming at all, that (2) an even greater part of the total warming occurred before the air's CO2 concentration began increasing in earnest (approximately 1930, which is actually close to the time when warming peaked in the United States and many other parts of the world), and that (3) the lion's share of the warming of the past nearly two centuries must therefore owe its existence to something other than rising atmospheric CO2 concentrations.
|Sherwood, Keith and Craig Idso|
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Esper, J., Cook, E.R. and Schweingruber, F.H. 2002. Low-frequency signals in long tree-ring chronologies for reconstructing past temperature variability. Science 295: 2250-2253.
Gonzalez-Rouco, F., von Storch, H. and Zorita, E. 2003. Deep soil temperature as proxy for surface air-temperature in a coupled model simulation of the last thousand years. Geophysical Research Letters 30: 10.1029/2003GL018264.
Jomelli, V. and Pech, P. 2004. Effects of the Little Ice Age on avalanche boulder tongues in the French Alps (Massif des Ecrins). Earth Surface Processes and Landforms 29: 553-564.
Le Roy Ladurie, E. 1983. Histoire du climat depuis l'an mil. Flammarion, Paris, France.
Lindzen, R.S. 2002. Do deep ocean temperature records verify models? Geophysical Research Letters 29: 10.1029/2001GL014360.
Mann, M.E., Bradley, R.S. and Hughes, M.K. 1998. Global-scale temperature patterns and climate forcing over the past six centuries. Nature 392: 779-787.
Mann, M.E., Bradley, R.S. and Hughes, M.K. 1999. Northern Hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophysical Research Letters 26: 759-762.
Moore, G.W.K., Holdsworth, G. and Alverson, K. 2002. Climate change in the North Pacific region over the past three centuries. Nature 420: 401-403.
Reynaud, L. 2001. Historie des fluctuations des glaciers en remontant le Petit Age de Glace. Colloque SHF variations climatiques et hydrologie. Paris, France, pp. 43-49.
Vincent, C. 2001. Fluctuations des bilans de masse des glaciers des Alpes francaises depuis le debut du 20em siecle au regard des variations climatiques. Colloque SHF variations climatiques et hydrologie. Paris, France, pp. 49-56.
Vincent, C. 2002. Influence of climate change over the 20th century on four French glacier mass balances. Journal of Geophysical Research 107: 4-12.
Vincent, C. and Vallon, M. 1997. Meteorological controls on glacier mass-balance: empirical relations suggested by Sarennes glaciers measurements (France). Journal of Glaciology 43: 131-137.
Yoo, JC. and D'Odorico, P. 2002. Trends and fluctuations in the dates of ice break-up of lakes and rivers in Northern Europe: the effect of the North Atlantic Oscillation. Journal of Hydrology 268: 100-112.