For some time, climate realists have been claiming that NOAA has altered or otherwise manipulated U.S. climate data in order to construct warming trends. California may provide a useful exhibit as to the “unique” nature of warming trends over the past 30 years in the NOAA National Climatic Data Center (NCDC) database, and raises even more concerns over what NOAA is doing to the data.

According to the NOAA-NCDC database, which forms the core of NOAA's reporting on climate change in the United States, there has been a strong increase in California's statewide average annual temperature since 1984 -- on the order of 2.1°F per century, although the trend isn't significant (p=0.16 parametric, p=0.14-0.22 non-parametric). There are seven climate divisions throughout California in the NOAA-NCDC database. All seven climate divisions have positive correlations in average annual temperatures during the past 30 years according to NOAA-NCDC, although only one of the divisions (the Southeast Desert Basins) has a significant trend. Nonetheless, NOAA-NCDC shows each portion of the state as having a positive correlation in average annual temperatures for the past three decades (i.e., the alarmists use this as evidence the state is warming rapidly as atmospheric greenhouse gas concentrations also rise).

Then we can go to the NOAA National Weather Service database and download the average annual temperature data for the following 14 climate regions within the state of California. And look what we find.

Out of 14 regions in the NOAA-NWS database, 11 (i.e., 79 percent) exhibit a negative -- not positive -- correlation in average annual temperatures over the past 30 years, and three of these cooling trends are statistically significant. In contrast, only three regions have positive (warming) correlations, and only one of these is significant.

Based on this NOAA-NWS data, California has most certainly not been warming over the past three decades. On the contrary, it appears the state has been cooling -- in complete contrast to the NOAA-NCDC database and its magical algorithms for calculating statewide and regional temperatures. There is a scientific Pandora's Box to be opened on the raw climate datasets, and if California is any indication, the results will not be favorable for the alarmists.