Climate Indices for Use in Social and Behavioural Research

This report describes the use of factor analysis in creating five climate indices from a set of 37 original variables. These variables represent all the major components of near-surface climate variation within the US. Data for 216 first-order weather stations were taken from the Local Climatological Data series of the National Oceanic and Atmosphere Administration. Principal components analysis with viramax rotation was applied to the 37 variables shown, reflecting 87.8% of the total variance which can be represented by just five factors. The first factor represent winters temperature and snowfall; the second is a summer air-moisture indicator; the third represents winter conditions; the fourth represents summer maximum daily temperature; and the fifth is primarily a wind-speed indicator. Taken together, the results confirm that American climates are dominated by strong seasonal influences. This suggests that the factor structure has not changed over time.