The Science Seminar Series: March 26, 2009 4pm
Are There Spuriously Induced Temperature and Precipitation Trends in the Southeast United States?
Dr. Jason Allard
Department of Physics, Astronomy, and Geosciences
Valdosta State University
Time: 4:00 - 5:00pm
The National Climatic Data Center (NCDC) has subdivided the contiguous United States into 344 climate divisions – areas representing nearly homogeneous climate regions. Forty-five of these climate divisions comprise the six state region of the Southeast U.S. While these data have been used in a variety of capacities, some argue that these data should be used judiciously, particularly with decadal- to century-scale climate change studies. The problem is that long-term trends in these data may be spuriously generated by the methods used to calculate the divisional datasets. These methods involve using all data available at a given time within a division, despite changes in the total number of stations and their locations through time. This study documents differences in annual temperature and precipitation trends between the NCDC Climate Division database and the United States Historical Climate Network (USHCN) for the Southeast United States. Correlation and multiple regression techniques indicate that the migration of the mean latitude, longitude, and elevation of NCDC stations within climate divisions impact the magnitude and the direction (i.e., increasing or decreasing) of the trends present in the divisional climate data relative to the USHCN dataset. These results are statistically significant, and explain some of the variances between the temperature and precipitation trends of the two datasets.