Friday, January 15, 2021

GISS reports 2020 as warmest year (virtual tie with 2016).

GISS reports 2020 as warmest year (virtual tie with 2016).

The GISS V4 land/ocean temperature anomaly was 0.81°C in December 2020, down from 1.13°C in November. That made the 2020 average 1.02°C, to 2 decimals the same as 2016. NOAA, like TempLS, had 2020 very slightly behind (by 0.02°C, vs TempLS 0.005°C).

None of these differences are significant. I calculated that if just one week had been 0.26°C warmer in 2020, TempLS would have rated 2020 warmest. In mid-December, the daily average fell by about 0.4°C and stayed low. If that had been delayed by a week, that would have made the difference.

Jim Hansen's report, with many more details, is 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. Thank you for the report!
    You comment that; " None of these differences are significant. I calculated that if just one week had been 0.26°C warmer in 2020, TempLS would have rated 2020 warmest."
    There is of course no significant difference in the annual temperature between 2016 and 2020, but without the outlier anomaly observed in november, 2020 would have been more clearly behind 2016.
    The last 6 months of GISS anomalies are as follows; 90 87 99 89 111 81 , which demonstrates that november was more than 0,2 degrees warmer than both the month ahead and the month following november. This suggest that special weather conditions were present in november, and limited to land temperatures. HADSST3 reported an anomaly of 0.508 in Oct, compared to 0.491 in Nov, and then a further drop to 0.401 in dec.
    Nevertheless, 2020 has been surprisingly warm considering the weak Nino-conditions one year ago, and it will be interesting to see whether this represents a new temperature level under ENSO-neutral conditions.
    Best regards; T. Klemsdal, Oslo.

  2. I update my prediction for GISS temperature anomaly using data up to Dec20.
    J-D20 1.02 finally
    DJF21 0.92+-0.14 drop by 0.19
    MAM21 0.93+-0.16 drop by 0.09
    JJA21 0.92+-0.13 drop by 0.05
    SON21 0.99+-0.14 drop by 0.06
    J-D21 0.95+-0.11 drop by 0.09

    In the last months there was an extrem tic toc between warmer and cooler months. Aug, Oct, Dec cooler, Sep, Nov warmer.
    Despite of the large drop in December the year 2020 was slightly warmer than 2016 by 0.003, so breaking the 2016 record without a strong El Nino.
    There is the largest month to month change up to now. I will need using MEI2 data in the future. Maybe the results will be get better than.
    Now it gives a 9% chance of breaking this new record again in 2021.