Monday, January 25, 2010

U.S. surface temperature data are reliable – no bias from station siting

Prominent global warming contrarian’s cherry-picked stations show no deviation from the warming trend.

All USHCN surface temperature stations and cherry-picked stations, 1950-2009. NCDC

Q. What can we say about poor station exposure and its impact on national temperature trends?

A. has examined about 70% of the 1221 stations in NOAA’s Historical Climatology Network (USHCN) (Watts, 2009). According to their web site of early June 2009, they classified 70 USHCN version 2 stations as good or best (class 1 or 2). The criteria used to make that classification is based on NOAA’s Climate Reference Network Site Handbook so the criteria are clear. But, as many different individuals participated in the site evaluations, with varying levels of expertise, the degree of standardization and reproducibility of this process is unknown. However, at the present time this is the only large scale site evaluation information available so we conducted a preliminary analysis.

Two national time series were made using the same homogeneity adjusted data set and the same gridding and area averaging technique used by NOAA’s National Climatic Data Center for its annual climate monitoring. One analysis was for the full USHCN version 2 data set. The other used only USHCN version 2 data from the 70 stations that classified as good or best. We would expect some differences simply due to the different area covered: the 70 stations only covered 43% of the country with no stations in, for example, New Mexico, Kansas, Nebraska, Iowa, Illinois, Ohio, West Virginia, Kentucky, Tennessee or North Carolina. Yet the two time series, shown below as both annual data and smooth data, are remarkably similar. Clearly there is no indication from this analysis that poor station exposure has imparted a bias in the U.S. temperature trends. …

Talking Points related to concerns about whether the U.S. temperature record is reliable [pdf]

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