Dr. Roger Pielke Jr. says exactly what I thought: this new paper from Rahmstorf is untrustworthy.
Here is another good example why I have come to view parts of the climate science research enterprise with a considerable degree of distrust.
A paper was released yesterday by PNAS, by Stefan Rahmstorf and Dim Coumou, which asserts that the 2010 Russian summer heat wave was, with 80% probability, the result of a background warming trend. But if you take a look at the actual paper you see that they made some arbitrary choices (which are at least unexplained from a scientific standpoint) that bias the results in a particular direction.
Look at the annotated figure above, which originally comes from an EGU poster by Dole et al. (programme here in PDF).
It shows surface temperature anomalies in Russia dating back to 1880. I added in the green line which shows the date from which Rahmsdorf and Coumou decided to begin their analysis — 1911, immediately after an extended warm period and at the start of an extended cool period.
Here’s the abstract:
Increase of extreme events in a warming world
+ Author Affiliations
Edited by William C. Clark, Harvard University, Cambridge, MA, and approved September 27, 2011 (received for review February 2, 2011)
We develop a theoretical approach to quantify the effect of long-term trends on the expected number of extremes in generic time series, using analytical solutions and Monte Carlo simulations. We apply our method to study the effect of warming trends on heat records. We find that the number of record-breaking events increases approximately in proportion to the ratio of warming trend to short-term standard deviation. Short-term variability thus decreases the number of heat extremes, whereas a climatic warming increases it. For extremes exceeding a predefined threshold, the dependence on the warming trend is highly nonlinear. We further find that the sum of warm plus cold extremes increases with any climate change, whether warming or cooling. We estimate that climatic warming has increased the number of new global-mean temperature records expected in the last decade from 0.1 to 2.8. For July temperature in Moscow, we estimate that the local warming trend has increased the number of records expected in the past decade fivefold, which implies an approximate 80% probability that the 2010 July heat record would not have occurred without climate warming.
Compare that to what NOAA says about it here