Changes in atmospheric concentrations of carbon dioxide during the last century have prompted concern about the effects of related changes in the earths climate, and, in turn, their effects on terrestrial ecosystems. It has been predicted that northern latitudes will experience the greatest increase in mean winter temperatures. In higher latitude regions, there is a tendency for warmer winters to be more snowy. Earlier researchers hypothesize that increased CO2 concentrations will reduce shortwave radiation absorbed by active snow layers and therefore delay the onset of spring snowmelt. However, a CO2 induced warming trend has been hypothesized by Foster (1989) to result in an earlier snowmelt date in the arctic and, therefore, an overall increase in the length of the snow-free period. Global change has the potential for altering date of snowmelt on the coastal plain of the Arctic National Wildlife Refuge (ANWR). Increased precipitation may result in delayed melting of an increased snow pack, delayed green-up and changes in forage availability. Alternatively, warmer air temperatures may accelerate snow melt and have an effect on vegetation phenology. Changes in timing of snowmelt may have measurable effects on migratory caribou that use the coastal plain. The timing of calving and the selection of calving sites in the Porcupine Caribou Herd (PCH) have been associated with degree of snowmelt. Early or late snowmelt caused by global change may affect surface and subsurface moisture levels through changes in the depth of the permafrost layer. Changes in hydrology and soil temperature may affect tundra vegetation production, phenology, and forage quality, which would, in turn have an effect on movements, condition, and survival of large herbivores of the coastal plain. Weather data at micro- and meso-scales from the Brooks divide to the coastal plain within the Arctic National Wildlife Refuge is not available from conventional sources. The Service has recently established 6 remote weather stations to collect air temperature and humidity, wind speed and direction, solar radiation, and barometric pressure measurements from the coastal plain and adjoining foothills. The resulting data will enable micro- and meso-scale interpretation of weather and weather patterns within the 2.5 million acre study area. Information collected and analyzed in this study will assess the potential impacts of climate change on use of the resources by herbivores.