NOAA Declares Hottest July – But Don’t Know How They Did The Math

Paul Homewood goes right to the source.

The real mystery, though, is how they arrive at the 1934 number. There are State Climatological Reports available from then, but no direct comparison can be made with current ones because there were less stations then and they were allocated to only three divisions instead of six. Also the majority of stations reporting in 1934 no longer report now. (For interest, the State temperature given at the time for July 1934 was 78.8F, i.e. 0.2F higher than now shown).

When I asked Deke Arndt of NOAA how they calculated the temperatures for 1934, he seemed as confused as me!

“Climate divisions weren’t in use then, so the circa 1934 is likely a straight up average of available stations at “press time”

The more modern CAG value uses the CDs to build the state value (this is a factor if stations are distributed unevenly within the state), it incorporates the late-arriving (in 1934) stations, several QA tests, etc.

Those are probably the factors in play here.”

So it would appear the temperatures that NOAA now declare for 1934 are no more than a “theoretical reconstruction”. But without the transparency to show how this has been done, how can we have any confidence that it has been done properly. There is a potential discrepancy of 0.6F in Virginia; if this is extended across the whole country, it would destroy the claim that this July was the hottest month on record as July 1936 was only 0.13F cooler on NOAA’s record. Indeed this would only the 5th warmest July in the CONUS.

Hottest July In Virginia? Or Maybe Not. « NOT A LOT OF PEOPLE KNOW THAT