Roy Spencer, PhD. Roy Spencer, PhD.
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U.S. Surface Temperature Update for July, 2012: +1.11 deg. C

The U.S. lower-48 surface temperature anomaly from my population density-adjusted (PDAT) dataset was 1.11 deg. C above the 1973-2012 average for July 2012, with a 1973-2012 linear warming trend of +0.145 deg. C/decade (click for full-size version):

I could not compute the corresponding USHCN anomaly this month because it appears the last 4 years of data in the file is missing (ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2/monthly/9641C_201208_F52.avg.gz). Someone please correct me if I am mistaken.

Note that the 12-month period ending in July 2012 is also the warmest 12-month period in the 40 year record. I cannot compare these statistics to the (possibly warmer) 1930s because for the most part only max and min temperatures were reported back then, and my analysis depends upon 4x/day observations at a specific synoptic reporting times.

There is also no guarantee that my method for UHI adjustment since 1973 has done a sufficient job of removing UHI effects. A short description of the final procedure I settled on for population density adjustment of the surface temperatures can be found here.

arrow6 Responses

  1. 28 mos ago

    Al I can say is, it is the global temperatures that matter, not the United States.

  2. 28 mos ago

    In repect to conflicing views. I say CO2 had no effect on the temperature rise last century. I feel past data supports this claim.

    I also think going forward, future data will just confirm what the past data is strongly suggesting.

  3. Peter Hartley
    28 mos ago

    It is interesting that the trend is quite close to the Watts et al (2012) trend of +0.155 deg C/decade for the Class 1/2 stations using their new classification system. While you do not have to worry about TOBS bias by definition, they were criticized for ignoring TOBS bias when using max and min observations only. Perhaps the similarity of their results with yours suggests that the TOBS bias adjustment (the largest adjustment made to the official temperatures) is unjustified.

    Another thought — I wonder how many of your specific synoptic reporting time observations pertain to stations they have classified according to siting criteria? It might be interesting to look at the fixed time of day observations for stations in different Classes. Perhaps your co-author Christy, who also co-authored the Watts et al paper might be interested in following up that issue.

  4. sky
    28 mos ago

    While the last 12 months indeed have been very warm in the lower 48, the yearly average is still well below what was experienced in the 1920s and 1930s at vetted nonurban stations. Without at least a century of data, “record” temperatures are not very significant in the climatic context, with its distinct, albeit highly irregular, multidecadal swings back and forth.

  5. Roy
    28 mos ago

    Just curious — would it be reasonable to restrict the data to just daily low temperatures rather than mixing up four readings per day? My thought is that the atmosphere cycles through temperatures over the course of the day, that the real issue is the heat retained at the end of the daily cycle and that transient heat absorbed (sorry if that’s the wrong word) during the day and radiated off through the night is not all that important… Thanks!

  6. Villabolo
    28 mos ago

    Curious as to why it was the “lower U.S.”. Why was Alaska left out?