Joe Gathman writes: > There's a pretty impressive time-series animation of > arctic ice shrinking at this page: > > http://www.washingtonpost.com/wp-dyn/content/article/ > 2007/10/21/AR2007102100761.html?hpid=topnews&sid=ST20071021007 > > I showed it today at the beginning of class. It takes > no time and makes quite an impact.
On the subject of climate change and potential impact in front of a class, there was a nice 11-minute segment during this last Sunday's "60 Minutes" on the rise of megafires in the American West due to climate change: http://www.cbsnews.com/sections/i_video/main500251.shtml?id=3389657n In the piece, Scott Pelley interviews Thomas Swetman (U Arizona) who has long argued that small differences in temperature and rainfall synergistically work to promote subcontinental periods of fire across the western US. The Science papers they talk about in the CBS piece are probably these two: ===================================================== Science 31 August 1990: Vol. 249. no. 4972, pp. 1017 - 1020 DOI: 10.1126/science.249.4972.1017 Fire-Southern Oscillation Relations in the Southwestern United States Thomas W. Swetnam 1 and Julio L. Betancourt 2 1 Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721 2 U.S. Geological Survey, 1675 West Anklam Road, Tucson, AZ 85705 Fire scar and tree growth chronologies (1700 to 1905) and fire statistics (since 1905) from Arizona and New Mexico show that small areas burn after wet springs associated with the low phase of the Southern Oscillation (SO), whereas large areas burn after dry springs associated with the high phase of the SO. Through its synergistic influence on spring weather and fuel conditions, climatic variability in the tropical Pacific significantly influences vegetation dynamics in the southwestern United States. Synchrony of fire-free and severe fire years across diverse southwestern forests implies that climate forces fire regimes on a subcontinental scale; it also underscores the importance of exogenous factors in ecosystem dynamics. ===================================================== Science 5 November 1993: Vol. 262. no. 5135, pp. 885 - 889 DOI: 10.1126/science.262.5135.885 Fire History and Climate Change in Giant Sequoia Groves Thomas W. Swetnam 1 1 Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721 Fire scars in giant sequoia [Sequoiadendron giganteum (Lindley) Buchholz] were used to reconstruct the spatial and temporal pattern of surface fires that burned episodically through five groves during the past 2000 years. Comparisons with independent dendroclimatic reconstructions indicate that regionally synchronous fire occurrence was inversely related to yearly fluctuations in precipitation and directly related to decadal-to-centennial variations in temperature. Frequent small fires occurred during a warm period from about A.D. 1000 to 1300, and less frequent but more widespread fires occurred during cooler periods from about A.D. 500 to 1000 and after A.D. 1300. Regionally synchronous fire histories demonstrate the importance of climate in maintaining nonequilibrium conditions. ===================================================== As we talked about a couple of years ago on the list, the presence of subcontinental-scale megafire seasons has been a minor curiosity of mine for some time, particularly as a result of the major climate transition that occurred during the last phase of the Pleistocene to the current Holocene. The alpine/boreal forest ecosystem that inhabited the valley floors in Arizona and New Mexico, where I am, moved up the side of mountains with the retreat of the glaciers. The nagging question has always been: how fast did these ecosystems move? It's always been my prejudice that it probably changed quite quickly, perhaps in only a century or so. The megafires that the West is experiencing now would certainly suggest such a possibility, even though the extent of current climate change is only a small fraction of that that occurred just before the onset of the Holocene. Swetman says essentially the same thing in the CBS clip. It doesn't take much of a drop in precipitation and rise in temperature to stress a conifer forest and make it very vulnerable to burning. On a second subject, here are some NASA satellite pictures of the California wildfires taken yesterday. Of interest, note the size of the growth of the fire just north of Los Angeles in four hours and the thousand-mile plume of smoke over the Pacific that's resulting from the fires: http://www.nasa.gov/vision/earth/lookingatearth/socal_wildfires_oct07.html Wirt Atmar AICS Research, Inc University Park, NM 88003-4691 USA (575) 524-9800 (575) 526-4700 fax [EMAIL PROTECTED] [EMAIL PROTECTED] [EMAIL PROTECTED] http://aics-research.com/research/
