Volume 16, Number 3: 16 January 2013
Lest we forget, it is worth reflecting now and again about the claim of NASA's James Hansen - which he made in his 26 April 2007 testimony to the Select Committee of Energy Independence and Global Warming of the U.S. House of Representatives - that life in earth's alpine regions is in danger of being "pushed off the planet" as the earth warms, since it has "no place else to go."
At first blush the claim sounds logical enough; but when scrutinized more closely, it is found to be much like a French pastry: lots of appealing fluff, but little of real substance. Many are the studies we have reviewed on our website that illustrate this important fact: see Extinction (Real World Observations - Plants: Migrating). And now comes another study that drives yet another stake into the heart of Hansen's claim.
Graham et al. (2012) introduce their approach to the subject by noting that "local scale patterns in soil topography, substrate structure, plant cover, and soil moisture content have strong impacts on soil and plant microclimate in rugged alpine habitats," where local topography "has been shown to have a strong influence on the extremes and dynamics of alpine soil temperatures," as illustrated by the work of Wundram et al. (2010). They also note, in this regard, that "soil surface temperature in alpine microclimates may deviate significantly from air temperature, adding complexity to patterns of surface temperatures," as described by Scherrer and Korner (2010, 2011). And they say "it is not surprising, therefore, that local topography has a significant impact on alpine species distributions (Korner, 2003; Loffler and Pape, 2008; Jakalaniemi, 2011)," a factor that is nowhere to be found, much less considered, in Hansen's pontifical declaration.
So what new real-world data and consequent insights do Graham et al. bring to the subject? The six U.S. scientists employed what they describe as "a novel mobile system to examine changes in soil and plant canopy surface temperatures at spatial scales of centimeters and temporal scales of minutes in an alpine fellfield habitat [a typically rock-strewn area that is above the timberline and dominated by low plants such as grasses and sedges] in the White Mountains of California." And what did they find? They discovered that in the middle of a typical summer day, the mean surface temperature differences between points 2, 5 and 10 cm apart were 2.9, 5.4 and 9.0°C, respectively, while extreme differences of 18°C or more were sometimes found over distances of just a few centimeters.
With respect to the implications of their findings, Graham et al. state that "the magnitude of temperature variation at these fine scales is greater than the range of warming scenarios in Intergovernmental Panel on Climate Change (IPCC) projections, suggesting that these habitats offer the capacity of significant thermal heterogeneity for plant survival." Put another way, they say that "these traits of microclimate for alpine habitats suggest that models predicting upslope movements of species under increasing temperatures may not be entirely realistic and that there may well be sufficient microclimate heterogeneity to slow such migration."
Further to this point, the six scientists note that Scherrer and Korner (2010, 2011) "used infra-red thermometry with an image resolution of about 1 m2 to document a large and persistent variation in microhabitat temperatures over mesoscale alpine landscape terrain, mimicking temperature gradients present along elevational gradients of several hundred meters." And they say that these observations, together with theirs, suggest that "alpine plants under global change may well find appropriate thermal niches for establishment and survival over very short distances without elevational shifts," which carefully drawn conclusion once again contradicts the bloviating and unsubstantiated declaration of NASA's James Hansen on this important matter.
Sherwood, Keith and Craig Idso
Graham, E.A., Rundel, P.W., Kaiser, W., Lam, Y., Stealey, M. and Yuen, E.M. 2012. Fine-scale patterns of soil and plant surface temperatures in an alpine fellfield habitat, White Mountains, California. Arctic, Antarctic, and Alpine Research 44: 288-295.
Jakalaniemi, A. 2011. Narrow climate and habitat envelope affect the survival of relict populations of a northern Arnica angustifolia. Environmental and Experimental Botany 72: 415-421.
Korner, C. 2003. Alpine Plant Life. Springer Verlag, Berlin, Germany.
Loffler, J. and Pape, R. 2008. Diversity patterns in relation to the environment in alpine tundra ecosystems of northern Norway. Arctic, Antarctic, and Alpine Research 40: 373-381.
Scherrer, D. and Korner, C. 2010. Infra-red thermometry of alpine landscapes challenges climatic, warming projections. Global Change Biology 16: 2602-2613.
Scherrer, D. and Korner, C. 2011. Topographically controlled thermal-habitat differentiation buffers alpine plant diversity against climate warming. Journal of Biogeography 38: 406-416.
Wundram, D., Pape, R. and Loffler, J. 2010. Alpine soil temperature variability at multiple scales. Arctic, Antarctic, and Alpine Research 42: 117-128.