The map here is from NOAA Paleoclimatology, which is the study of past climate, for times prior to instrumental weather measurements. Obvious sections of the topic are tree-rings and caves (with the layers of dripping preserved in rock. Less obvious are ways paleoclimatologists learn from paleofire, plant macros, insects and pollen. The borehole section includes the interactive map, which is an internet tool for digging into what is known about what is known about past climate.
