Guest Post By Walter Dnes

In continuation of my Temperature Anomaly projections, the following are my April projections, as well as last month’s projections for March, to see how well they fared.

The Data Sources

The latest data can be obtained from the following sources

Miscellaneous Notes
At the time of posting 5 of the 6 monthly data sets were available through March 2017. HadCRUT4 is available through February 2017. The NCEP/NCAR re-analysis data runs 2 days behind real-time. Therefore, real daily data from March 31st through April 28th is used, and the 29th is assumed to have the same anomaly as the 28th.

The projections for the surface data sets (HadCRUT4, GISS, and NCEI) are derived from the previous 12 months of NCEP/NCAR anomalies compared to the same months’ anomalies for each of the 3 surface data sets. For each of the 3 data sets, the slope() value (“m”) and the intercept() value (“b”) are calculated. Using the current month’s NCEP/NCAR anomaly as “x”, the numbers are plugged into the high-school linear equation “y = mx + b” and “y” is the answer for the specific data set. The entire globe’s NCEP/NCAR data is used for HadCRUT, GISS, and NCEI.

For RSS and UAH, subsets of global data are used, to match the latitude coverage provided by the satellites. This month, the RSS version 4.0 data set has been added, while retaining the version 3.3 data set that had been identified as simply “RSS” in previous posts. RSS version 4.0 has similar global coverage to UAH v6, so the same NCEP/NCAR data subset is used for the projections. RSS version 3.3 has its own subset.

For the satellite data sets the monthly anomaly difference (current month minus previous month) in the NCEP/NCAR subset anomalies is multiplied by the slope() of the previous 12 months, and added to the previous month’s anomaly.

The NCEP/NCAR anomalies (especially the satellite subsets) have dropped noticably for April. I’m a bit nervous about the low projections for the satellite data sets. But I continue to follow the algorithm projections. This is no place for “gut feeling”.

The graph immediately below is a plot of recent NCEP/NCAR daily anomalies, versus 1994-2013 base, similar to Nick Stokes’ web page. The second graph is a monthly version, going back to 1997. The trendlines are as follows…

• Black – The longest line with a negative slope in the daily graph goes back to early July, 2015, as noted in the graph legend. On the monthly graph, it’s August 2015. This is near the start of the El Nino, and nothing to write home about. Reaching back to 2005 or earlier would be a good start.
• Green – This is the trendline from a local minimum in the slope around late 2004, early 2005. To even BEGIN to work on a “pause back to 2005”, the anomaly has to drop below the green line.
• Pink – This is the trendline from a local minimum in the slope from mid-2001. Again, the anomaly needs to drop below this line to start working back to a pause to that date.
• Red – The trendline back to a local minimum in the slope from late 1997. Again, the anomaly needs to drop below this line to start working back to a pause to that date.

NCEP/NCAR Daily Anomalies:

NCEP/NCAR Monthly Anomalies: