Hydrology and freshwater ecology
The hydrological system is potentially very sensitive to changes in climate. Changes in precipitation affect the magnitude and timing of runoff and the frequency and intensity of floods and droughts; changes in temperature result in changes in evapotranspiration, soil moisture, and infiltration. The resulting changes in surface wetness, reflectivity, and vegetation affect evapotranspiration and the formation of clouds, as well as surface net radiation and precipitation. Meanwhile, the hydrological system is being affected by other, more direct human activities, such as deforestation, urbanization, and water-resource exploitation. The effects of climate change on hydrological regimes are generally estimated by combining catchment-scale hydrological models with climate change scenarios derived from general circulation model (GCM) output. In addition to the uncertainties associated with GCM simulations, there are three major problems in estimating the hydrological effects of climate change: (1) expressing scenarios at a scale appropriate for hydrological modeling; (2) the considerable errors inherent in climatic and hydrological data used to validate hydrological models; and (3) converting climatic inputs into hydrological responses. Methods have been developed to address most of these problems, but estimates of the hydrological effects of climate change remain very uncertain. This uncertainty is largely due to difficulties in defining credible scenarios for changes in precipitation and assessing vegetation response to a changed atmosphere at appropriate spatial scales.
Cambridge University Press