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Is Global Climate Becoming More Variable?
Volume 17, Number 7: 12 February 2014

Several months ago, in a paper published in Nature, Huntingford et al. (2013) wrote that "there is considerable interest in determining whether global warming is increasing climate variability," due to the concerns of some scientists (of the climate-alarmist variety) that an increase in climate variability could result in more extreme types of weather. And, therefore, concerned about the study of Hansen et al. (2012) - which had purported to find, in Huntingford et al.'s words, that "seasonal mean temperatures are starting to show increased variability, with a particularly large difference between the 1970s and the 1980s" - they decided to take a closer look at the problem.

Working with global temperature data for the period 1984-2006, the five researchers were able to demonstrate that in spite of the fact that "fluctuations in annual temperature have indeed shown substantial geographical variation over the past few decades, the time-evolving standard deviation of globally averaged temperature anomalies has been stable."

The reason for their result being so different from that of Hansen et al. was that whereas Hansen et al.'s approach to the problem focused on normalized temperature anomalies, they employed absolute values, which ultimately enabled them to declare, in the final sentence of their paper's abstract, that "our findings contradict the view that a warming world will automatically be one of more overall climatic variation," and which led them to state in the title of their paper that there will be "no increase in global temperature variability despite changing regional patterns." And they cited as still further real-world evidence for this conclusion - in the opening sentence of their paper's abstract - that "evidence from Greenland ice cores shows that year-to-year temperature variability was probably higher in some past cold periods," citing Steffensen et al. (2008). And on top of all of that evidence, they reported that when the absolute global standard deviation for the ERA-Interim (Dee et al., 2011) period (1984-2006) is plotted, it is clearly evident that "rather than increasing, [it] is actually found to be decreasing in the most recent years."

And so it would appear that there is nothing unusual, unnatural or unprecedented about the course of earth's climate over the past several decades, during which time the anthropogenic-induced increases in the atmosphere's CO2 concentration have been significantly enhancing the water use efficiency and productivity of the planet's many natural and agricultural ecosystems.

Sherwood, Keith and Craig Idso

Dee, D., Uppala, S. M., Simmons, A. J., Berrisford, P., Poli, P., Kobayashi, S., Andrae, U., Balmaseda, M. A., Balsamo, G., Bauer, P., Bechtold, P., Beljaars, A. C. M., van de Berg, L., Bidlot, J., Bormann, N., Delsol, C., Dragani, R., Fuentes, M., Geer, A. J., Haimberger, L., Healy, S. B., Hersbach, H., Hˇlm, E. V., Isaksen, L., Kňllberg, P., K÷hler, M., Matricardi, M., McNally, A. P., Monge-Sanz, B. M., Morcrette, J.-J., Park, B.-K., Peubey, C., de Rosnay, P., Tavolato, C., ThÚpaut, J.-N. and Vitart, F. 2011. The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Quarterly Journal of the Royal Meteorological Society 137: 553-597.

Hansen, J., Sato, M. and Ruedy, R. 2012. Perception of climate change. Proceedings of the National Academy of Sciences USA 109: E2415-E2423.

Huntingford, C., Jones, P.D., Livina, V.N., Lenton, T.M. and Cox, P.M. 2013. No increase in global temperature variability despite changing regional patterns. Nature 500: 327-330.

Steffensen, J.P., Andersen, K.K., Bigler, M., Clausen, H.B., Dahl-Jensen, D., Fischer, H., Goto-Azuma, K., Hansson, M., Johnsen, S.J., Jouzel, J., Masson-Delmotte, V., Popp, T., Rasmussen, S.O., Rothlisberger, R., Ruth, U., Stauffer, B., Siggaard-Andersen, M.-L., Sveinbj÷rnsdˇttir, A.E., Svensson, A. and White, W.C. 2008. High-resolution Greenland Ice Core data show abrupt climate change happens in few years. Science 321: 680-684.