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Has There Been an Increase in Multi-Day Temperature Variability in Austria in Response to 20th-Century Warming?
Reference
Hiebl, J. and Hofstatter, M. 2012. No increase in multi-day temperature variability in Austria following climate warming. Climatic Change 113: 733-750.

Background
Is earth's weather getting more extreme and variable in response to the warming that plucked the planet out of the chilly grip of the Little Ice Age? Climate alarmists claim that it should have been doing so; and in a review of this significant question, Easterling et al. (2000) go even further, stating that data in support of this proposition "would add to the body of evidence that there is a discernible human effect on the climate."

What was done
In a study designed to assess the extent to which temperature variability may have increased in Austria since the late 19th century, Hiebl and Hofstatter take a systematic and objective approach to the issue - at least for the climate element of air temperature and on a local scale - based on 140 years of data from Vienna-Hohe Warte, Kremsmunster, Innsbruck-University, Sonnblick and Graz-University.

What was learned
Starting from a low level of temperature variability around 1900, the two Austrian researchers report there was a slow and steady rise in variability during the whole 20th century. However, they also indicate there was a "period of persistently high variability levels before 1900," which led them to say that the "relatively high levels of temperature variability during the most recent warm decades from 1990 to 2010 are put into perspective by similar variability levels during the cold late 19th century." In fact, they state that "when compared to its inter-annual fluctuations and the evolution of temperature itself, high-frequency temperature variability in the course of the recent 117-139 years appears to be a stable climate feature." In other words, high-frequency temperature variability over the past century or more would appear to be the norm and unrelated to anthropogenic activities.

What it means
Hiebl and Hofstatter conclude that concerns about "an increasing number and strength of temperature extremes in terms of deviations from the mean state in the past decades cannot be maintained," according to their study; and, therefore, they state that related "exaggerated statements seem irresponsible." And we agree.

Reference
Easterling, D.R., Evans, J.L., Groisman, P.Ya., Karl, T.R., Kunkel, K.E., and Ambenje, P. 2000. Observed variability and trends in extreme climate events: A brief review. Bulletin of the American Meteorological Society 81: 417-425.

Reviewed 28 November 2012