THE PERSISTENCE OF WEATHER. Although there seems to be nothing reliable about the weather, especially when planning a picnic, there is actually a (very) long range consistency at work. Armin Bunde (armin.bunde@theo.physik.uni-giessen.de) at the University of Giessen, and his colleagues from Milan, Potsdam, and the Bar-Lan University (Israel) have now conducted the most thorough multi-year study yet of correlations in daily temperature records. What they do in effect is to ask: if the weather is sunny and warm today, what will be the likelihood that it will be sunny and warm tomorrow, and the next day, and after x days? Choosing randomly 14 meteorological stations worldwide---ranging from Pendleton, Colorado (with 57 years of data) to Prague (with the longest daily temperature record, 218 years)---and factoring out seasonal effects by comparing not temperatures but departures from the average daily temperature, they are able to tease out the persistent rhythms of temperature. As expected, they observed that after x days, the weather is less and less likely to be similar to that on day 1. In particular, they find (1) that the falloff in correlation is not exponential in nature (e to the -x power) as many had thought; rather it obeys a power-law rule (i.e., the correlation is actually proportional to x raised to some exponent); (2) the exponent, with a value of -0.65, is the roughly the same for all the cities; and (3) the persistence of this behavior seems to hold over at least a decade and maybe as long as a century or more. (Koscielny-Bunde et al., Physical Review Letters, 20 July; visit Physics News Preview.)