 The Bergeron and Spatial Synoptic Classification systems focus on the origin of air masses that define the climate of a region.Paleoclimatology is the study of ancient climates.Since very few direct observations of climate are available before the 19th century, paleoclimates are inferred from proxy variables that include non-biotic evidence such as sediments found in lake beds and ice cores, and biotic evidence such as tree rings and coral.