Reposted from the latest edition of The NIPCC Report:
Climate alarmists vociferously contend that greenhouse-gas-induced global warming is responsible for creating more frequent and greater extremes of weather of all types, such as extremely hot summers and excessively dry or wet seasons. But are they correct in this contention?
In an effort designed to broach this question, Bohm (2012) first states that "South Central Europe is among the spatially densest regions in terms of early instrumental climate data," citing Auer et al. (2007); and he goes on to state that this fact allows for successfully testing for homogeneity and developing "a larger number of very long instrumental climate time series at monthly resolution than elsewhere," - which he thus proceeds to do - noting that the resulting long time series subset of the greater alpine region provides a great potential for analyzing high frequency variability from the preindustrial (and mostly-naturally-forced) period to the "anthropogenic climate" of the past three decades. More specifically, he reports that "the unique length of the series in the region allowed for analyzing not less than 8 (for precipitations 7) discrete 30-year 'normal periods' from 1771-1800 to 1981-2010."
As articulated by Bohm, "the overwhelming majority of seasonal and annual sub-regional variability trends is not significant." In the case of precipitation, for example, he writes that "there is a balance between small but insignificant decreases and increases of climate variability during the more than 200 years of the instrumental period," while in the case of temperature he reports that "most of the variability trends are insignificantly decreasing." And in a "special analysis" of the recent 1981-2010 period that may be considered the first "normal period" under dominant greenhouse-gas-forcing, he finds all extremes "remaining well within the range of the preceding ones under mainly natural forcing." And he notes that "in terms of insignificant deviations from the long-term mean, the recent three decades tend to be less rather than more variable [italics added]."
The study's main result - in the concluding words of the Austrian researcher at the Central Institute for Meteorology and Geodynamics in Vienna - is "the clear evidence that climate variability did rather decrease than increase over the more than two centuries of the instrumental period in the Greater Alpine Region [GAR], and that the recent 30 years of more or less pure greenhouse-gas-forced anthropogenic climate were rather less than more variable than the series of the preceding 30-year normal period." Put another way, greenhouse-gas-induced warming has not led to more frequent and/or greater extremes of either precipitation or temperature in the GAR, in clear refutation of the climate-alarmist claim as to what, in their view of the subject, should have been occurring.
Auer, I., Boehm, R., Jurkovic, A., Lipa, W., Orlik, A., Potzmann, R., Schoener, W., Ungersboeck, M., Matulla, C., Briffa, K., Jones, P., Efthymiadis, D., Brunetti, M., Nanni, T., Maugeri, M., Mercalli, L., Mestre, O., Moisselin, J.-M., Begert, M., Mueller-Westermeier, G., Kveton, V., Bochnicek, O., Stastny, P., Lapin, M., Szalai, S., Szentimrey, T., Cegnar, T., Dolinar, M., Gajic-Capka, M., Zaninovic, K. and Majstorovic, Z. 2007. HISTALP - Historical Instrumental climatological Surface Time series of the greater ALPine Region. International Journal of Climatology 27: 17-46.
Abstract from the Bohm paper:
The European Physical Journal Plus, Volume 127, article id. #54
The paper uses the data potential of very long and homogenized instrumental climate time series in the south central Europe for analyzing one feature which is very dominant in the climate change debate --whether anthropogenic climate warming causes or goes along with an increase of climate extremes. The monthly resolved data of the HISTALP data collection provide 58 single series for the three climate elements, air pressure, air temperature and precipitation, that start earlier than 1831 and extend back to 1760 in some cases. Trends and long-term low frequent climate evolution is only shortly touched in the paper. The main goal is the analysis of trends or changes of high frequent interannual and interseasonal variability. In other words, it is features like extremely hot summers, very cold winters, excessively dry or wet seasons which the study aims at. The methods used are based on detrended highpass series whose variance is analyzed in discrete 30-year windows moving over the entire instrumental period. The analysis of discrete subintervals relies on the unique number of 8 (for precipitation 7) such "normal periods". The second approach is based on the same subintervals though not in fixed but moving windows over the entire instrumental period. The first result of the study is the clear evidence that there has been no increase of variability during the past 250 years in the region. The second finding is similar but concentrates on the recent three decades which are of particular interest because they are the first 30 years with dominating anthropogenic greenhouse gas forcing. We can show that also this recent anthropogenic normal period shows no widening of the PDF (probability density function) compared to the preceding ones. The third finding is based on the moving window technique. It shows that interannual variability changes show a clear centennial oscillating structure for all three climate elements in the region. For the time being we have no explanation for this empirical evidence. We argue that it should not be an artifact of any remaining data problems, but of course a centennial cyclic effect based on 250 years of data only is not really well consolidated in terms of sample length. But it is at least an interesting new feature and the subject is open for scientific discussion and for further studies dealing with circulation effects, long-term memories in the oceans etc.