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.

May global surface TempLS down 0.17°C from April.

The TempLS mesh anomaly (1961-90 base) was 0.844deg;C in May vs 1.014°C in April. This drop was larger the fall in the NCEP/NCAR reanalysis base index, which was 0.064°C. ERA5 showed a near-identical fall of 0.07 °C. By contrast again, the UAH satellite data for the lower troposphere showed a rise of 0.16°C.

Other reports on the reanalysis emphasised that despite the fall from April, it was still the warmest May in the record. That is true for TEmpLS too (just); May 2016 anomaly was 0.825°C.

The most prominent feature is again a very warm N Siberia, extending into the Arctic. By contrast N America except for the Pacific coast, and Eastern Europe were cool.

Last month I commented on the timing of posting, noting that now a lot of GHCN V4 data becomes available very promptly, and then there is a trickle of late data, which can sometimes have an outsize effect on the result. That creates a dilemma about whether to wait. That month the late data did not make much difference. This month the flow of data has been similar; we have 8599 stations to date, but there may be 1000 more to come, eventually. There has been little new data in the last three days. So we'll see.

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


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

NCEP/NCAR reanalysis May 2020 surface temperature down 0.064°C from April.

The Moyhu NCEP/NCAR index came in at 0.337°C in May, following 0.401°C in April, on a 1994-2013 anomaly base. It makes May the coolest month since January 2019.

Karsten Haustein commented that NCEP/NCAR had been showing some strange effects in March/April not seen in ERA5, say, and this could be part of a spurious cooling. There has been some disparity also with TempLS and other surface measures. I think the primary value of this NCEP/NCAR index has been to show changes over short time periods. I don't compare over long periods or calculate long term records. The reason is that I don't think reanalysis offers long term homogeneity; there is a changing mix of instrumentation, for example. This oddity may be a case in point that means one should not make too much of a one-time shift.

The map shows most of N America very cool, and also Northern Europe and a band from Iran to China. Warm patches in Arctic and N central Siberia. Australia cool, Antarctica mostly warm. We'll see if that is borne out by other indices. The BoM agrees Australia was cool.

Update: The UAH satellite temperatures are out; they showed a rise of 0.16°C. The map is here. It is a similar pattern, but cold places are not nearly as cold as the reanalysis, and the warm places warmer.