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Summer Moisture Variability Throughout Europe Over the Course of the 20th Century
Reference
van der Schrier, G., Briffa, K.R., Jones, P.D. and Osborn, T.J. 2006. Summer moisture variability across Europe. Journal of Climate 19: 2818-2834.

What was done
The authors constructed monthly maps of the Self-Calibrating Palmer Drought Severity Index (SC-PDSI, a variant put forward by Wells et al. (2004) of the more common PDSI) for the period 1901-2002 for Europe (35N-70N, 10W-60E), which index, in their words, "improves upon the PDSI by maintaining consistent behavior of the index over diverse climatological regions," which "makes spatial comparisons of SC-PDSI values on continental scales more meaningful."

What was learned
Van der Schrier et al. report that "over the region as a whole, the mid-1940s to early 1950s stand out as a persistent and exceptionally dry period, whereas the mid-1910s and late 1970s to early 1980s were very wet." Over the entire study period, however, they found that trends in the continent's summer moisture availability "fail to be statistically significant, both in terms of spatial means of the drought index and in the area affected by drought." In addition, they note that "evidence for widespread and unusual drying in European regions over the last few decades [as suggested by the work of Briffa et al. (1994) and Dai et al. (2004)] is not supported by the current work," in that "values for the total percentage area subject to extreme moisture conditions in the years 1996-99 returned to normal levels at ~2% from a maximum of nearly 10% in 1990." In further support of their findings, the four researchers note that "the absence of a trend toward summer desiccation has recently also been observed in soil moisture records in the Ukraine (Robock et al., 2005) and supports conclusions in the current study."

What it means
Contrary to the fact that "most global climate model simulations of the future, when forced with increasing greenhouse gases and anthropogenic aerosols, predict summer desiccation in the midlatitudes of the Northern Hemisphere (e.g., Gregory et al., 1997; Wetherald and Manabe, 1999; Cubasch et al., 2001)," as reported by Robock et al., such has not been found to be the case in the real world, in spite of what climate alarmists routinely describe as the unprecedented (over the past two millennia) global warming of the 20th century.

References
Briffa, K.R., Jones, P.D. and Hulme, M. 1994. Summer moisture variability across Europe, 1892-1991: An analysis based on the Palmer Drought Severity Index. International Journal of Climatology 14: 475-506.

Cubasch, U., Meehl, G.A., Boer, G.J., Stouffer, R.J., Dix, M., Noda, A., Senior, C.A., Raper, S. and Yap, K.S. 2001. Projections of future climate change. In: Houghton, J.T. et al. (Eds.), Climate Change 2001: The Scientific Basis: Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, New York, USA, pp. 525-582.

Dai, A., Trenberth, K.E. and Qian, T. 2004. A global dataset of Palmer Drought Severity Index for 1870-2002: Relationship with soil moisture and effects of surface warming. Journal of Hydrometeorology 5: 1117-1130.

Gregory, J.M., Mitchell, J.F.B. and Brady, A.J. 1997. Summer drought in northern midlatitudes in a time-dependent CO2 climate experiment. Journal of Climate 10: 662-686.

Robock, A., Mu, M., Vinnikov, K., Trofimova, I.V. and Adamenko, T.I. 2005. Forty-five years of observed soil moisture in the Ukraine: No summer desiccation (yet). Geophysical Research Letters 32: 10.1029/2004GL021914.

Wells, N., Goddard, S. and Hayes, M.J. 2004. A self-calibrating Palmer Drought Severity Index. Journal of Climate 17: 2335-2351.

Wetherald, R.T. and Manabe, S. 1999. Detectability of summer dryness caused by greenhouse warming. Climatic Change 43: 495-511.

Reviewed 27 December 2006