Technical Abstract: Theory relating changes in the area-average evaporation from a landscape with changes in the evaporation from pans or open water within the landscape is developed. Such changes can arise in two ways, by Type (a) processes related to large-scale changes in atmospheric concentrations and circulation that modify surface evaporation rates in the same direction, and by Type (b) processes related to coupling between the surface and ABL at landscape scale that usually modify area-average evaporation and pan evaporation in different directions. The theoretical basis for interrelating evaporation rates in response to Type (a) changes in climate is derived. They have the same sign, and they have broadly similar magnitude except for area-average evaporation which responds to area-average surface resistance. The results of previous modeling studies that investigate surface-atmosphere coupling are parameterized and, as an alternative to assuming the Complementary Evaporation hypothesis, used to develop a theoretical description of Type (b) coupling via the vapor pressure deficit in the ABL. This theory shows that the interrelationship between appropriately normalized pan and area-average evaporation rates varies significantly with temperature and wind speed but on average changes are approximately equal and opposite. Long-term Australian pan evaporation data are then analyzed to demonstrate the simultaneous presence of Type (a) and (b) processes, and observations from three field sites in southern Arizona are analyzed to confirm the theory describing Type (b) coupling via vapor pressure deficit.