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.

TempLS global surface 2020 just cooler than 2016 (virtual tie).

TempLS December 2020 results are in, and that makes a complete average for 2020. I had calculated that a December average anomaly (1961-90) of over 0.681°C would be enough to make 2020 the hottest year, which seemed quite likely, given the November average was 0.891°C and the lowest month of 2020 to date was 0.704°C. However, December was very cool, at 0.628°C, a drop of 0.263°C. That meant that 2020 averaged 0.852°C, whereas 2016 was 0.857°C. Here is a table of those TempLS anomaly averages:

Nov 2020	0.891	Ave 2016	0.857
Dec 2020	0.628	Ave 2020	0.852
Diff	0.263	Diff	0.005

The TempLS result is based on 8603 land stations of GHCN V4 which have reported to date, along with ERSST. More (about 800) land stations will post results during January, and this will alter the result a little. An increase of 0.054°C needed to put 2020 ahead is possible, but not very likely. TempLS usually matches GISS NASA fairly well, but given the closeness, whether GISS 2020 comes out ahead is not predictable from this.

The cool December was foreshadowed in the NCEP/NCAR reanalysis tracking, which also showed a drop of 0.263°C. The first part of the month was warm, but after about ten days there was a drop of about 0.4°C, and no recovery.

The main very cool region was over Kazakhstan and parts of Russia nearby, with an extension over Mongolia and into China. The ENSO region of the Pacific coast, and also SE, was cool (La Nina). Elsewhere it was mostly (relatively) warm, especially around the Arctic, extending into Canada and Scandinavia. Most of Europe was warm, and also the Sahara.

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


 

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