Sunday, June 3, 2018

May NCEP/NCAR global surface anomaly down by 0.09°C from April

In the Moyhu NCEP/NCAR index, the monthly reanalysis anomaly average fell from 0.377°C in April to 0.287°C in May, 2018. This cancels out the last two months of increase, and matches the February average.

It was for once warm in both in North America (except far N) and Europe especially Scandia. Russia was cold in the W, warm in the East. Nothing special at either pole. Probably the main contributor to the drop was a chill in the N Atlantic region, including Greenland. Active map here.

I had thought that the gradual warming might be associated with the decline of La Niña. But the changes are small, so shouldn't be over-interpreted. The BoM still says that ENSO is neutral, and likely to stay so for a few months.

This post is part of a series that has now run for some years. The NCEP/NCAR integrated average is posted daily here, along with monthly averages, including current month, and graph. When the last day of the month has data (usually about the 3rd) I write this post.
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 Nick, two brief comments. First: last La Nina event was weak and so with little influence on global temperature, if any. Second: usually the global effect takes place with some 3-4 months delay, if compared with the rise of SST in equatorial Pacific. This rise was evident during April, so I think we maybe could see some rising global anomalies, but not before August. However, we could see larger and unpredictable monthly fluctuations, too... Gianni (Bologna-Italy)

  2. The preliminary NOAA CDAS GMSTA for May based on daily averages was down -0.135 C from April and was the lowest monthly anomaly since July 2015. WeatherBELL also reported a monthly GMSTA average based on NOAA CDAS that was down by -0.131 C for May from April. Karsten Haustein's GFS GISS-adjusted average for May was down by -0.080 C from April and was the lowest since January (only 0.003 C higher) and his NCAR R1 May average was down 0.064 C from April but not as low as February (0.043 C higher).

  3. For the record books.