An internal U.S. Forest Service report is circulating on how climate change is effecting the Tahoe National Forest and the neighboring El Dorado National Forest: A summary of current trends and probable future trends in climate and climate-driven processes in the Eldorado and Tahoe National Forests and the neighboring Sierra Nevada. The report was written by Chris Mallek, Department of Plant Sciences; University of California-Davis and Hugh Safford, Regional Ecologist, USDA Forest Service, Pacific Southwest Region.
The climate data in the report was derived from four weather stations with long-term meteorological records from the general area of the El Dorado and Tahoe National Forests. The stations were, Nevada City, Placerville, Truckee and Lake Spaulding. I have examined the Nevada City Station data here and the Placerville station here. This post will focus on the Truckee station.
From the report:
At the Truckee station, an increase in annual mean maximum temperatures drove
an increase of 1.5° F in the annual mean temperature between 1905 and 2008 (Fig. 2). Much like the trends recorded by stations at lower elevations, most of this increase occurred during the latter half of the 1900s (1949-2002).
There was no significant change in the min, with a 3.0° F degree increase in the max, creating a 1.5° F change in the mean. See Table 1 graphic below:
Here is a plot of the max temperature from Truckee COOP Station 049043 from 1949 to 2002 and from 1998 to 2008.
I cannot see the 1.5° F degree warming reported in the paper. Nor could I find any warming in the period from 1998 to 2008. Looking at the COOP record there was large gap in the record from 1920 to 1935. When I plotted the data from 1935 to 2008, I found about 1.5° F degree increase in the max temperature, which would result in a mean of about 0.75° F degrees if there was no significant change in the min.
If there was no temperature increase from 1949 to 2002, as shown above, it most have occurred prior to that time.
From the Truckee COOP data I think that we can conclude there is no significant warming at this station since 1949, calling in to question the warming reported in the paper. The next time I am in Truckee, I plan on visiting the station and take some pictures. The NOAA/NCDC station data when entered in Google Earth produces some inconsistent results.