Potential surface hydrologic responses to increases in greenhouse gas concentrations and land use and land cover changes

Abstract

To investigate the impacts of increased greenhouse gas (GHG) concentrations and land use and land cover change (LULCC) on various components of hydrologic cycle, three sets of numerical experiments were performed using the fully coupled Community Earth System Model (CESM). In the first set of experiments, GHG concentrations were set to preindustrial (1850) levels, but the land was set with potential and current vegetation cover. In the second set of experiments, GHG concentrations levels were set to present day (2000) and land covers were, again set to potential and current vegetation. The third set of experiments was same as the second one, except using a different version of CESM, to examine the reliability of LULCC‐induced climate effects. In the model, the increased GHG concentrations led to statistically significant increases in precipitation and evapotranspiration at mid‐ and high latitudes during both warm (May–September) and cold (November–March) seasons. LULCC caused the weakening hydrological cycle in eastern Asia, southern Asia, Europe, and the semi‐arid region of North America. During both seasons, LULCC plays relatively a more important role than increased GHG concentrations in changing evapotranspiration in southern Asia and Europe. In contrast, increased GHG concentrations play a dominant role in determining changes in evapotranspiration in the semi‐arid region of eastern Asia during the cold season, as well as changes in precipitation, evapotranspiration, and runoff at high latitudes during both seasons. In some regions, LULCC‐induced changes can compensate or equal to GHG‐induced changes in hydrological cycle, especially in evapotranspiration.