A summary of mean weather conditions over a time period, usually based on thirty years of records. Climates are largely determined by location with respect to land- and sea-masses, to large-scale patterns in the general circulation of the atmosphere, latitude, altitude, and to local geographical features. Safford provides a summary of the role of radiation in climate (1999, J. Biogeog. 26, 4), and of the regional atmospheric circulation (J. Biogeog. 26, 3). Feedbacks between land surface and atmosphere are also important determinants of climate (Knorr and Schnitzler (2006) Clim. Dynam. 26; G. Bonan 2002). Gallup et al. (1999) Int. Reg. Sci. Rev. 22, 2 argue that climate has large effects on income levels and income growth.