A little more searching turned up this NOAA/USHCN data set, which shows that the hottest summer (June-Aug) in recorded US history (contiguous 48 states, since 1895) is still 1936, so maybe 10% is closer to the truth. The 10 hottest US summers on record are 1936 (74.64 F), 2006 (74.36 F), 1934 (74.18 F), 2010 (73.96 F), 2002 (73.96 F), 1988, 2007, 2003, 1933, and 2001.
To make this needlessly precise, I fit a little model to the data and estimated that there’s a 7% chance of breaking the 1936 record and a 12% chance of topping the 2006 temperature. For the past few decades, it looks like there’s a linear trend plus some random noise. Fitting a line to the past 30 data points gives a .04/yr increase and puts the trend line at 73.35 F for 2011. The residuals have a standard deviation of .87. The record (74.64) is 1.29 degrees above the trend line for 2011, which makes it 1.48 standard deviations above the trend line. If the noise has a normal distribution, that would give a 7% chance of breaking the record (since p(z>1.48)=.07). A similar calculation gives a 12% chance of having the hottest summer of the past 70 years (breaking the 74.36 F mark set in 2006, which is 1.15 SDs above the trend line).
Thanks! I had a sense that the global warmth of recent years hadn’t necessarily translated into a record-breaking summer in the US, but I hadn’t looked into the data like this.
A little more searching turned up this NOAA/USHCN data set, which shows that the hottest summer (June-Aug) in recorded US history (contiguous 48 states, since 1895) is still 1936, so maybe 10% is closer to the truth. The 10 hottest US summers on record are 1936 (74.64 F), 2006 (74.36 F), 1934 (74.18 F), 2010 (73.96 F), 2002 (73.96 F), 1988, 2007, 2003, 1933, and 2001.
To make this needlessly precise, I fit a little model to the data and estimated that there’s a 7% chance of breaking the 1936 record and a 12% chance of topping the 2006 temperature. For the past few decades, it looks like there’s a linear trend plus some random noise. Fitting a line to the past 30 data points gives a .04/yr increase and puts the trend line at 73.35 F for 2011. The residuals have a standard deviation of .87. The record (74.64) is 1.29 degrees above the trend line for 2011, which makes it 1.48 standard deviations above the trend line. If the noise has a normal distribution, that would give a 7% chance of breaking the record (since p(z>1.48)=.07). A similar calculation gives a 12% chance of having the hottest summer of the past 70 years (breaking the 74.36 F mark set in 2006, which is 1.15 SDs above the trend line).
Thanks! I had a sense that the global warmth of recent years hadn’t necessarily translated into a record-breaking summer in the US, but I hadn’t looked into the data like this.