Global Warming Science -

San Diego, CA - Cooling for the last 50 Years

[last update: 2010/08/09]



San Diego 2010 - Missing Summer


Friday Aug 6, 2010, NBC San Diego: “July proved to be nearly the coldest on record in nearly a hundred years. Now, 6 days into August, our unseasonably cool weather continues, and today we have a chance of seeing the coolest August day since record keeping began in 1875. … Since weather records began, the official high temperature reading at Lindbergh Field has never been lower than 66 degrees on an August day. National Weather Service thinks we may see a high of 65 today, making it the new record.” []


Of course weather isn't climate (although climate is weather averaged over 30 years), so a cold summer doesn't mean anything. The following figure shows the San Diego maximum July-August temperatures for 1955-2009. There is a cooling trend in summer temperatures in San Diego over the last 50 years. So this summer of 2010 is consistent with the trend.


(San Diego/Lin is the NOAA GHCN station at Lindbergh Field referred to in the NBC article above.)

(All graphs in this article plotted at: [])




San Diego Temperature Trends


San Diego has been experiencing cooling for the last 50 years. The following figure shows the average annual temperature anomaly for San Diego from the NOAA GHCN database compared with the Hadley CRUTEM3 database for 1980-2009. The linear trend is statistically significant - San Diego shows significant cooling over the last 30 years.




While 30 years is climate, it is not long-term climate. However, one must keep in mind that according to the IPCC the models can reproduce the global warming prior to 1970 using only natural forcings, as shown in the following figure - their claim is that warming since 1970 is due to anthropogenic CO2 (see




In a CRU email exchange from Edward Cook to Michael Mann in 2001, Cook said "I think that most researchers in global change research would agree that the emergence of a clear greenhouse forcing signal has really only occurred since after 1970. I am not debating this point, although I do think that there still exists a significant uncertainty as to the relative contributions of natural and greenhouse forcing to warming during the past 20-30 years at least." []


The following figure shows the average annual temperature anomaly for San Diego from the NOAA GHCN database compared with the Hadley CRUTEM3 database for 1955-2009. There is no statistically significant warming or cooling trend. However, a significant warming event occurred in 1976 - this is the 1976 Pacific climate shift.




Hare and Mantua (“Empirical evidence for North Pacific regime shifts in 1977 and 1989”, Progress in Oceanography, 2000) state: “It is now widely accepted that a climatic regime shift transpired in the North Pacific Ocean in the winter of 1976–77. This regime shift has had far reaching consequences for the large marine ecosystems of the North Pacific. Despite the strength and scope of the changes initiated by the shift, it was 10–15 years before it was fully recognized. Subsequent research has suggested that this event was not unique in the historical record but merely the latest in a succession of climatic regime shifts.” []


The following figure shows the annual average maximum and minimum temperature for San Diego from the NOAA GHCN database for 1955 - 2009. The effect of the 1976 Pacific climate shift is clearly observable - there are cooling trends before and after. The maximum temperature (blue) has been cooling more rapidly than the minimum temperature (red).



For more info on the 1976 climate shift, see:




Pacific Decadal Oscillation


The Pacific coast of the United States is highly influenced by the Pacific Ocean temperatures and the Pacific Decadal Oscillation (PDO). The following figure shows the PDO [].




The following figure is from a NOAA study of the impact of the PDO variability on the California Current ecosystem and shows the approximately 60-year cycle of the PDO and the corresponding northern Pacific Ocean temperature regimes []



The following figure shows the NOAA sea surface temperature anomalies for August 2, 2010, showing a clear cold phase pattern of the PDO []




The following figure shows the GHCN and HadCRU annual average temperature anomaly for San Diego for 1955-2009 shown previously, changed to green and superimposed on the PDO.




Atmospheric CO2 has been constantly increasing throughout this period. But that is irrelevant to temperatures.



For more info on the PDO see: