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Climate Variability in a Warming World: The Situation in Switzerland
Reference
Beniston, M. and Goyette, S. 2007. Changes in variability and persistence of climate in Switzerland: Exploring 20th century observations and 21st century simulations. Global and Planetary Change 57: 1-15.

Background
The authors report that "it has been assumed in numerous investigations related to climatic change that a warmer climate may also be a more variable climate (e.g., Katz and Brown, 1992; IPCC, 2001; Schar et al., 2004)," and they note that "such statements are often supported by climate model results, as for example in the analysis of GCM and/or RCM simulated temperature and precipitation (Mearns et al., 1990, 1995) or in multiple-model simulations over Europe."

What was done
Beniston and Goyette investigate "whether, based on long time-series of observational data, [the above] hypothesis is indeed verified in a climate that has experienced a warming of 2°C or more at certain locations in Switzerland since the beginning of the 20th century," focusing on "two Swiss sites representative of low elevations (Basel, 369 m above sea level) and high elevations (Saentis, 2500 m above sea level)."

What was learned
The two Swiss researchers determined that "for these locations, the inter-annual and decadal variability of both maximum and minimum daily temperatures has in fact decreased [their italics] over the course of the 20th century, despite the strong warming that has been observed in the intervening period," and they write that their findings "are consistent with the temperature analysis carried out by Michaels et al. (1998), where their results also do not support the hypothesis that temperatures have become more variable as global temperatures have increased during the 20th century." In addition, they found that "the principal reason for this reduction in variability is related to the strong increase in the persistence of certain weather patterns at the expense of other types."

What it means
Contrary to climate model predictions that temperature becomes more variable as the climate warms, Swiss temperature data from both high and low elevations indicate that temperatures there have actually done just the opposite over the course of the 20th century, during which time climate alarmists claim the earth experienced unprecedented global warming. Since this is also the case with many other parts of the world (see Weather Extremes (Temperature) in our Subject Index), these findings highlight a major problem associated with the climate modeling enterprise.

References
IPCC. 2001. Climate Change 2001: The Scientific Basis. Cambridge University Press, Cambridge, UK.

Katz, R.W. and Brown, B.G. 1992. Extreme events in a changing climate: variability is more important than averages. Climatic Change 21: 289-302.

Mearns, L.O., Schneider, S.H., Thompson, S.L. and McDaniel, L.R. 1990. Analysis of climate variability in general circulation models: comparison with observations and change in variability in 2 x CO2 experiments. Journal of Geophysical Research 95: 20,469-20,490.

Mearns, L.O., Giorgi, F., McDaniel, L. and Shields, C. 1995. Analysis of variability and diurnal range of daily temperature in a nested regional climate model: comparison with observations and doubled CO2 results. Climate Dynamics 11: 193-209.

Michaels, P.J., Balling Jr., R.C., Vose, R.S. and Knappenberger, P.C. 1998. Analysis of trends in the variability of daily and monthly historical temperature measurements. Climate Research 10: 27-33.

Shar, C., Vidale, P.L., Luthi, D., Frei, C., Haberli, C., Liniger, M. and Appenzeller, C. 2004. The role of increasing temperature variability in European summer heat waves. Nature 427: 332-336.

Reviewed 17 October 2007