Support For Klotzbach Et Al (2009) In The 1997 Easterling Et Al Science Paper “Maximum And Minimum Temperature Trends For The Globe”

There is further support for our paper

Klotzbach, P.J., R.A. Pielke Sr., R.A. Pielke Jr., J.R. Christy, and R.T. McNider, 2009: An alternative explanation for differential temperature trends at the surface and in the lower troposphere. J. Geophys. Res., accepted.

The support is from an unlikely source, a 1997 paper

David R. Easterling, Briony Horton, Philip D. Jones, Thomas C. Peterson, Thomas R. Karl, David E. Parker, M. James Salinger, Vyacheslav Razuvayev, Neil Plummer, Paul Jamason, Christopher K. Folland, 1997: Maximum and Minimum Temperature Trends for the Globe. Science Volume 277 18 July1997.

The abstract of their paper reads

“Analysis of the global mean surface air temperature has shown that its increase is due, at least in part, to differential changes in daily maximum and minimum temperatures, resulting in a narrowing of the diurnal temperature range (DTR). The analysis, using station metadata and improved areal coverage for much of the Southern Hemisphere landmass, indicates that the DTR is continuing to decrease in most parts of the world, that urban effects on globally and hemispherically averaged time series are negligible, and that circulation variations in parts of the Northern Hemisphere appear to be related to the DTR. Atmospheric aerosol loading in the Southern Hemisphere is much less than that in the Northern Hemisphere, suggesting that there are likely a number of factors, such as increases in cloudiness, contributing to the decreases in DTR.”

In their paper, they present a figure (their Figure 1) of long term trends over land for maximum and minimum temperatures. The figure caption for the figure reads

“Time series of annual average maximum temperature, minimum temperature, and DTR for (A) the globe, using all available stations, (B) the globe, using only nonurban stations, (C) Chile and Argentina, using only nonurban stations, and (D) Southeast Asia, using only nonurban stations. The heavy line is the result of smoothing with a nine-point binomial filter with reflected ends. Trends (slopes) for the maximum temperatures in (C) and (D) are not statistically significant at the 0.05 level (two-tailed t test).”

For the time period 1949 to 1993 for the global using all available stations, they show a slope of 0.88C per hundred years for the maximum temperature, but over double that of 1.86C per hundred years for the minimum temperatures. This warming is seen in each of their plots in their Figure 1. In fact, for (D), Southeast Asia, while they report a cooling of -0.43C per hundred years for the maximum temperatures (although not statistically significant), they still report a statistically significant linear slope of +2.16C per hundred years for the minimum temperatures.

The presence of a warm bias in the surface temperature record associated with the minimum temperatures (a bias when used to diagnose temperature trends through the lower troposphere) that we reported on in our paper Klotzbach et al 2009 is provided further evidence on its robustness from the Easterling et al 1997 paper.