Understanding Agricultural and Urban Land Cover Impacts on Regional Climate  

Michael Puma
          
Human-induced changes in land cover are increasingly recognized as important for predicting regional 
climate change.  In fact, the climate impacts of increasing CO2 may be regionally masked or enhanced 
depending on both the location and nature of land cover change.  In addition, these land cover changes are 
being intensified, primarily through the growth of agriculture (irrigation) and urbanization, such that their 
climate impacts may become more significant in the future.  Here, I present results based on simulations 
with the GISS ModelE general circulation model, which are focused on agricultural and urban impacts on 
regional climate.   My colleagues and I find evidence that expected warming trends from increased 
greenhouse gas forcing have been locally 'masked' by irrigation induced cooling, and it is uncertain how 
the magnitude of this irrigation masking effect will change in the future.  More preliminary results on urban 
affects on regional climate will also be presented, where we focus on how urban hydrologic controls 
influence regional changes in temperature and precipitation.