Honolulu Temperature Record in the 1940s – Wrong?
By: oceanclimate, July 09, 2009

Few weeks ago in June run a story about the temperature recording at Obs Oahu/Honolulu. (HERE) The story covers a number of complaints[1], but with regard the 1940s it says: “It also looks like the station was moved about 1949, or something happened around the station environment.”[2] In deed the GISS/NASA image (see: first/left) indicate a drop in annual mean temperatures between 1945 and 1949 from app. 24.8° to 22.8°C. The change is grossly out of tune with the mean before 1939 (app. 23.8°) and the mean between 1960 and 1980 (app. 24.0°C).  The matter could quickly be assumed as a runaway value, but it shouldn’t, if been put in the appropriate context.

In the 1940s the location of Obs Oahu is special as it harbors Pearl Harbor the naval center during WWII in the Pacific, and at least until the end of the Korean War in 1953. On the 7th December 1941 Japan ambushed Pearl Harbor and thereby forced the United States to become a war party (INFO: PDF­-10MB;) . Since fall 1939 the fortification of Pearly Harbour under a National Defense construction program was underway (INFO).   The temperature climbed significantly from 1939 to 1945.

Until the surrender of Japan in August 1945 the USA the Pacific in the west of Hawaii had been subject to naval war activities never experienced before and thereafter. When the US Navy operated with many thousand ships and airplanes in the Western Pacific, Japan experienced the coldest winter on record  in 1944 (lef) . In the city of Kyoto it was the coldest    

since app. 1895 (see image below). Had that been caused by the naval war activities in complex sea areas?  As it may be, it seems evident that throughout the Northern Hemisphere the sea surface temperatures trend changed towards cooling since the early  1940 , see Fig.3 .

The trend was certainly also observable at Obs Oahu, but presumably was not the reason for the substantial temperature decrease at this station between 1945 and 1949. The most like reason was the present of the  huge naval armada at Pearl Harbor and their numerous activities concerning trails, training and exercises. It is in a sea area which is very deep and with abundantly cold water under a thin warm sea surface layer. While this explanation is not more than an option, it could be a mistake for not considering it seriously.

The previous comment was about:
The Arctic and the talking about the “Apocalypse Now”

Extract from Chapter 1 at:


[2] In reply to the essay, the web log was informed (June 19) : “The Geomag operations of the Honolulu observatory were moved in 1947”.  There is no indication that this has had an impact on the recording, the trend change came only after 1949, this matter is not further discussed here.