Climate models are extremely important tools for simulating and understanding climate, and they can provide credible projections of future climate change. Climate model projections are not predictions, but rather scenarios of how the climate might change based on observed patterns. Multiple models are often used to illustrate a range of possibilities.
Every model has an inherent degree of uncertainty, because its projections provide only a general picture of what to expect. For a region such as Western North Carolina, changes in climate will be highly variable due to the range of microclimates; climate models do not necessarily account for the variability. This uncertainty shows the importance of a regional approach to understanding the effects of changing conditions. With climate projections, uncertainty does not necessarily imply that change is unknown, but rather that future conditions involve variability.
The computer model developed by the Met Office Hadley Centre for Climate Change represents a 'warm and wet' future scenario. In Western North Carolina, the Hadley model shows moderately warmer air temperature and increased average precipitation by 2020.
Water stress is defined by the availability of water. Water stress impacts forests primarily by its affect on soil moisture. Soil moisture is important for biological processes and forest health, and soil moisture levels are determined both by temperature and precipitation. For Western North Carolina, soil moisture levels change due to the range of microclimates. The increases in precipitation for Western North Carolina with the Hadley model would generally increase soil moisture and, as a result, decrease water stress. However, while increasing precipitation alone would increase soil moisture, higher temperatures in some areas, resulting in greater evaporation, would offset the additional moisture. Some areas in Western North Carolina might experience more water stress conditions than others despite increased precipitation.
The climate change model developed by the Canadian Centre for Climate Modelling and Analysis represents a 'hot and dry' future scenario. For Western North Carolina, the Canadian model shows much higher average air temperature and decreased average precipitation.
Water stress and soil moisture levels are determined by temperature and precipitation. Much of Western North Carolina would experience great declines in soil moisture. The Canadian model depicts increases in water stress and other effects, such as increased drought.