Background
Noting that "almost every summer, there is a heat wave somewhere in the United States that garners popular media attention," the authors say that "a natural question arises: is global warming the cause of such heat waves or are they merely statistical fluctuations?" Adding that it is only "natural to be concerned that global warming is playing a role when there is a proliferation of record-breaking temperature events," they go on to analyze the subject in significant mathematical detail.

What was done
As Redner and Petersen describe it, they "theoretically study the statistics of record-breaking daily temperatures and validate these predictions using both Monte Carlo simulations and 126 years of available data from the city of Philadelphia." This they do using "extreme statistics" to "derive the number and the magnitude of record temperature events, based on the observed Gaussian daily temperature distribution in Philadelphia, as a function of the number of years of observation," after which they "consider the case of global warming, where the mean temperature systematically increases with time."

What was learned
At the end of their lengthy analysis, and after discussing its several intermediate findings, the two researchers say their "primary result is that we cannot yet distinguish between the effects of random fluctuations and long-term systematic trends on the frequency of record-breaking temperatures with 126 years of data," stating that "the current warming rate is insufficient to measurably influence the frequency of record temperature events."

What it means
The findings of this study would seem to suggest that it is not yet statistically justifiable to attribute any individual heat wave or "proliferation of record-breaking temperature events" to historical global warming, be it CO2-induced or otherwise, as so many climate alarmists are typically so quick to do.