Saturday, June 13, 2020

GISS May global down by 0.12°C from April.

The GISS V4 land/ocean temperature anomaly was 1.02°C in May 2020, down from 1.14°C in April. That compares with a 0.165deg;C fall in the TempLS V4 mesh index. As with TempLS, it was the warmest May in the record, despite the fall from April. Jim Hansen's report is here, with this graph of months in the last few years showing what happened here.

As usual here, I will compare the GISS and earlier TempLS plots below the jump.

Here is GISS V4

And here is the TempLS V4 LOESS-based plot

This post is part of a series that has now run for seven years. The GISS data completes the month cycle, and is compared with the TempLS result and map. GISS lists its reports here, and I post the monthly averages here.
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. Hi The year 2018 is missing.
    Thanks for good work!
    Martin Trittelvitz

    1. Thanks, Marty
      I don't know why 2018 is missing. It is not my plot, but from Jim Hansen's report (probably made by Dr Sato).

  2. And yet this May is cooler than last May in the NCEP/NCAR daily data you provide? Is there much reason for that difference?

    1. Peter,
      I post the NCEP/NCAR reanalysis data because I think it gives useful information on the within month scale, and particularly how the current month is headed. I think it is less reliable as a long term index, mainly because of lack of homogeneity. The mix of instruments changes. The data is compiled for the forecast timescale.

      GISS and TempLS both said that May 2020 was warmest, with May 2016 just a little way behind. FWIW I think that is the more reliable result.

  3. May 2020 ranked 4th for Mays back to 1948 in the NCEP/NCAR R1 Sigma 0.995 level (pressure level at 99.5% of surface pressure or roughly 50 meters above ground level) data set. Below are the top five May global mean Sigma 0.995 surface air temperature averages (degrees Celsius):

    2016 15.435
    2019 15.374
    2017 15.364
    2020 15.301
    2014 15.278

    I have compared the monthly average global mean surface air temperature anomalies versus those for the NCEI land/sea index and they compare reasonably well all the way back to 1948. Referenced to 1981-2010, NCEI reported an anomaly of 0.50C versus 0.462C calculated for NCEP/NCAR R1.

    1. Bryan,
      Yes, my results are quite similar
      2016 0.471
      2019 0.41
      2017 0.4
      2020 0.297
      2018 0.297

      ps sorry about occasional moderation delays. Unfortunately I am beset by spam at the moment, so moderation is needed.

  4. I update my prediction for GISS temperature anomaly using data up to May20.
    JJA20 0.94+-0.11
    SON20 1.04+-0.15
    J-D20 1.06+-0.07
    DJF21 1.07+-0.25
    MAM21 1.04+-0.20

    Now the prediction gives a 88 % chance of a new record this year.