Sunday, September 6, 2020

August global surface TempLS down 0.049°C from July.

The TempLS mesh anomaly (1961-90 base) was 0.725deg;C in August vs 0.774°C in July. This drop was less than the fall in the NCEP/NCAR reanalysis base index, which was 0.067°C. The UAH satellite data for the lower troposphere showed a smaller fall of 0.01°C.

There was a warm spot in N Central Siberia, and general warmth in the Americas, except for a region in the Mississippi area. Europe and N Africa were warm. Antarctica was mixed.

Here is the temperature map, using the LOESS-based map of anomalies.

As always, the 3D globe map gives better detail.

This post is part of a series that has now run since 2011. The TempLS mesh data is reported here, and the recent history of monthly readings is here. Unadjusted GHCN is normally used, but if you click the TempLS button there, it will show data with adjusted, and also with different integration methods. There is an interactive graph using 1981-2010 base period here which you can use to show different periods, or compare with other indices. There is a general guide to TempLS here.

The reporting cycle starts with a report of the daily reanalysis index on about the 4th of the month. The next post is this, the TempLS report, usually about the 8th. Then when the GISS result comes out, usually about the 15th, I discuss it and compare with TempLS. The TempLS graph uses a spherical harmonics to the TempLS mesh residuals; the residuals are displayed more directly using a triangular grid in a better resolved WebGL plot here.

A list of earlier monthly reports of each series in date order is here:

  1. NCEP/NCAR Reanalysis report
  2. TempLS report
  3. GISS report and comparison with TempLS


  1. Have you checked whether the July temperature has not also changed ? I find that the July value has increased by 0.04C with respect to its value a month ago. This must have something to do with the V4 homogenisation process.

    1. Clive,
      I posted 0.75°C for July; the current value is 0.779°C. I have been finding generally upward creep in late data. In fact August has already drifted up to 0.743, while this post of 6 August says 0.725°C.

      I had trouble earlier this year when a whole lot of results from GHCN V4 appeared early, tempting me to post, and then when a relatively few results came later, there was still a lot of drift relative to the station numbers. I looked into it, and corresponded with GHCN. There was data from quite a few places that just wasn't getting posted at all. I don't know why that should have had that effect, but it could induce bias. It seems to be mostly fixed now.

      In these posts I quote the difference between the latest estimate for both months, which leads to some inconsistency in headlines. Since the late drift does seem to be upwards, it creates a cooling trend, if you just looked at the headings. It's mature July vs new August, which will probably be warmer if seen later.

  2. So that looks like some station data for a given month can arrive long after the month has ended. But I also see changes between July 2020 and August 2020 dating way back to 2015 - eg
    Dec 2015 (July) = 1.031
    Dec 2015 (Aug) = 0.978

    So I reckon they must run a homogenisation algorithm every month.

    1. Clive,
      I'm using unadjusted data, which for each station doesn't change. I think the changes in aggregate are due to the added stations being somehow more likely to be warmer than they usually are.

      For Dec 2015 I posted 0.964°C in Jan 2016 (TempLS mesh). Current is 0.967; in August it was 0.965. I keep online a CSV record of historic global temperatures (many sources) as posted at end of each month. A typical URL is
      Just change the date in the obvious way.

    2. Nice!

      Why do you use the unadjusted data ?

    3. Clive,
      I've written here among other places, about the use of unadjusted. My feeling was that it should overall make little difference, and that is how it turned out. I think the adjustments are justified, but when people start claiming that they are the main source of warming, it is good to have an adjustment free index available. I especially think it makes no difference to the year to year results. I have spent a lot of effort comparing with GISS and others, and I think the small differences I get are not due to adjustment.

      Plus, I must say, the stability of unadjusted helps. While adjustment doesn't affect the global average much, there is quite a lot of flutter.