Within the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), the authors of the chapter focusing on snow, ice, and frozen ground (Chapter 4) state that “The cryosphere integrates climate variations over a wide range of time scales, making it a natural sensor of climate variability and providing a visible expression of climate change.” In their very next sentence, the authors concede that “the cryosphere has undergone large variations on many time scales associated with ice ages and with shorter-term variations.” This is a conscientious caveat to their report, because it is widely accepted that Earth’s cryosphere, or frozen realm, has changed significantly in the past with variability in planetary temperature. It should not be too difficult to understand the concept that periods of reduced snow and ice across Earth have historically coincided with planetary warmth. With a risk of tugging on that particular linchpin of Al Gore’s scientific knowledge, here comes new research findings associated with snowpack variability in the Andes Mountains of South America.
Outside of Antarctica, snow cover in the Southern Hemisphere has not received much attention in the climate change debate. In fact, within the snow, ice, and frozen ground chapter of the AR4, approximately 800 words along with three figures and one table are dedicated to snow cover variability in the Northern Hemisphere, compared to less than 400 words and no accompanying graphics for variability in the Southern Hemisphere. We’re here to help spread the word on findings from the southern half of Earth.
Very late in 2006, the Journal of Climate published the research work of Mariano Masiokas (Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales and Department of Geography, University of Western Ontario) and colleagues entitled “Snowpack variations in the central Andes of Argentina and Chile, 1951-2005: Large-scale atmospheric influences and implications for water resources in the region” (Masiokas et al. 2006). The research team used snow course data from each side of the central Andes in Chile and Argentina to develop the “first regional snowpack series.” The team employed the six longest and most complete snow course records for the 55-year period in the region, covering an area stretching from 30ºS to 37ºS latitude. Their variable for study is annual maximum snow water equivalent (MSWE).
The snowpack of the central Andes serves as much more than a monitor of climate change. The authors explain that “over 10 million people in Central Chile and central-western Argentina depend on the freshwater originating from the winter snowpack of the central Andes.” Alarming is their charge that “coupled atmosphere-ocean general circulation models especially targeted to investigate high-elevation sites” have indicated that “for the next 80 years the central Andes will probably experience significant temperature increases” (Bradley et al. 2004; Masiokas et al. 2006). To make matters worse, Masiokas et al. note that “independent general circulation model simulations also predict a significant decrease in precipitation over the region for the next five decades” (Cubasch et al. 2001). The combination of higher air temperature and less precipitation in the central Andes over the rest of this century is not the recipe for a problem-free regional water supply. The climate models seem to be sending a strong message to over 10 million people in Chile and Argentina. Surely this trend is already evident given the global warming of the past several decades that is supposedly unprecedented within Earth’s climate record, right? Wrong.
Masiokas et al. found no such trend in MSWE, stating that the regional record “shows a non-significant positive linear trend (+3.95% per decade) over the1951-2005 interval,” or an absolute increase of greater than 21% over the period (Figure 1). The group matched the MSWE record with mean monthly streamflow data for the primary rivers in the region. They found that river discharges on both sides of the central Andes “are strongly correlated with the snowpack record and show remarkably similar interannual variability and trends.”
Figure 1. The regional snowpack (MSWE) series from the central Andes expressed as percentages from the 1966–2004 base period. The dashed lines indicate one standard deviation in the 1951–2005 regional snowpack record. MSWE means for the 1951–76 and 1977–2005 periods are shown as thick horizontal lines.
The work is important for two reasons. First, it once again either proves that general circulation models are not completely reliable, or it shows that little or no climate change has occurred in the central Andes, or both. Second, it introduces snow cover data from the Southern Hemisphere – a rarity in climate change circles. Within the snow, ice, and frozen ground chapter of the IPCC’s AR4, South American snow cover is briefly mentioned among the few words dedicated to the Southern Hemisphere. One of the IPCC’s conclusions is derived from newspaper accounts: “A long-term increasing trend in the number of snow days was found in the eastern side of the central Andes region (33ºS) from 1885 to 1996, derived from newspaper reports of Mendoza City.” The other “conclusion” uses the altitude of the 0º Celsius line from atmospheric profile data at one location as a surrogate for the behavior of the snow line of the western Andes. But instead of the indirect evidence reported in the IPCC, Masiokas et al. provide data for the real thing—actual snow on the ground. In so doing, they shed more doubt on the reliability of global circulation models while boosting the hopes of more than 10 million people in Chile and Argentina.
Bradley, R. S., F. T. Keimig, and H. F. Diaz, 2004: Projected temperature changes along the American cordillera and the planned GCOS network. Geophysical Research Letters, 31, L16210, doi:10.1029/2004GL020229.
Cubasch, U., and Coauthors, 2001: Projections of future climate change. Climate Change 2001: The Scientific Basis, J. T. Houghton et al., Eds., Cambridge University Press, 525–582.
Lemke, P., J. Ren, R.B. Alley, I. Allison, J. Carrasco, G. Flato, Y. Fujii, G. Kaser, P. Mote, R.H. Thomas and T. Zhang, 2007: Observations: Changes in Snow, Ice and Frozen Ground. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Masiokas, M.H., R. Villalba, B.H. Luckman, C. Le Quesne, and J.C. Aravena. 2006: Snowpack variations in the central Andes of Argentina and Chile, 1951-2005: Large-scale atmospheric influences and implications for water resources in the region. Journal of Climate, 19, 6334-6352.