In the history of science, it is well known that motivated reasoning can revisit any number of old results in ignorance, be it accidental or not, of previous work. With bad luck authors of such a revelation have their work sent to those who have done the previous or perhaps just read it and remembered. With bad luck for the rest of the world not.
John Christy and Richard McNider have form on such things, and, of course Eli is talking about their latest damp squib, Time Series Construction of Summer Surface Temperatures for Alabama, 1883–2014, and Comparisons with Tropospheric Temperature and Climate Model Simulations, which appeared in the Journal of the American Meteorological Society C.
Victor Variable is. . . dubious
This post gives just few quick notes on the methodological aspects of the paper.Tamino has torn this apart showing that it is the result of a stroll through the garden of forking paths looking for something pleasing to the authors state of mind, that of all the ways to dice and slice the data the only one that met their requirements was summer surface temperature maxima in the state of Alabama
- They select data with a weak climatic temperature trend.
- They select data with a large cooling bias due to improvements in radiation protection of thermometers.
- They developed a new homogenization method using an outdated design and did not test it.
The area in the southeast US certainly contains enough data and is actually a light shade of blue and represents cooling trends on the order of -0.2 to -0.5C in the lightest shade and -0.5 to -0.8 in the next darkest shade. It’s unfortunate that they chose such ambiguous colors for these two important distinctions. Three of the pixels show a statistically significant cooling trend during this time period.
BTW, this so-called “warming hole” in the 20th century has been addressed in a few papers. For example,
Kunkel, K.E., X.-Z. Liang, J. Zhu, and Y. Lin, 2006: Can CGCMs simulate the Twentieth Century “warming hole” in the central United States. J. Climate, 19, 4137–4153.which, in the intro, states that
Trends in temperature during the period 1976–2000 for the summer season only (Folland et al. 2001) show an area of cooling in the central United States, centered somewhat to the north and west of the center of the area of annual cooling found by Folland et al. (2001) for the entire twentieth century; this area of summer cooling was termed a “warming hole” by Pan et al. (2004). Robinson et al. (2002) analyzed the 1951–97 period and found annual cooling in the south-central United States, centered somewhat to the west of the twentieth-century annual cooling area and to the south of the 1976–2000 summer cooling area, although overlapping both. The term warming hole will be adopted here to refer to the general phenomenon found in all of these studies while the region to be studied will overlap all of the above areas and will be defined based on both physical and societal considerations. In addition to the lack of warming on a centennial time scale, the multidecadal variations are an interesting and integral aspect and will be examined along with the century-scale trends.Folland et al is Chapter 2 of the IPCC WG1 TAR so not exactly hidden away and Pan et al is also out in the open, but the Google does well with "warming hole" taking Eli to a NASA web site that talks about a 2012 paper by Leibensperger, et al, which finds that
. . the regional radiative forcing from US anthropogenic aerosols elicits a strong regional climate response, cooling the central and eastern US by 0.5-1.0 °C on average during 1970-1990, with the strongest effects on maximum daytime temperatures in summer and autumn. Aerosol cooling reflects comparable contributions from direct and indirect (cloud-mediated) radiative effects. Absorbing aerosol (mainly black carbon) has negligible warming effect. Aerosol cooling reduces surface evaporation and thus decreases precipitation along the US east coast, but also increases the southerly flow of moisture from the Gulf of Mexico resulting in increased cloud cover and precipitation in the central US. Observations over the eastern US show a lack of warming in 1960-1980 followed by very rapid warming since, which we reproduce in the GCM and attribute to trends in US anthropogenic aerosol sources.
Our model results show that US anthropogenic aerosols can explain the observed lack of warming over the eastern US from 1930 to 1980 followed by very rapid post-1980 warming. Without US anthropogenic aerosol sources, we find in the model a relatively constant rate of warming over the 1950–2050 period, driven by increasing greenhouse gases. Increasing aerosols until 1980 offset the warming. Decreasing aerosol after 1980 accelerated the warming due to the loss of the aerosol cooling shield. We find that the observed warming from 1990 to 2010 is significantly greater than would have been expected from greenhouse gases alone.That aerosol has a lot of coal and uncontrolled auto exhaust in it. Good news is that the air is cleaner. Bad news is that the US Southeast is warming up even more. There is more work on this issue.
None of these papers are referenced by Christy and McNider. Perhaps Eli should Google it for them