Abstract
Land use has been recognized as an important anthropogenic forcing of climate change in recent studies. However, climatic effects of land management practices have been little discussed and compared to land-use impacts. As land-atmosphere interactions via surface fluxes are particularly strong during the warm season, we investigate the impacts of historical land use and present irrigation practices on summer temperatures in the Northern Hemisphere using the most recent version of Community Earth System Model. Our results suggest that historical land use leads to an overall cooling in the middle latitudes and a warming in the tropics, and the sign and magnitude of the changes in temperature depend on the type of land cover change. On the other hand, summer irrigation leads to a significant cooling over many irrigated areas due to enhanced evapotranspiration, and the local cooling is comparable to and even stronger than the land-use effects. Both land use and irrigation can also significantly influence the intensity and frequency of hot extremes. Land use shows stronger impacts during the night through ground heat flux feedback, while irrigation shows stronger impacts during the day through latent heat flux feedback. Our comparison demonstrates the importance of irrigation in local and regional climate, highlighting the necessity of considering such land management practices in future assessments of regional climate change and climate mitigation.
Highlights
It is widely recognized that land use/land cover change affects the overlying atmosphere through land-atmosphere interactions, and modifies the local and broader-scale climate
This study presents a comparison between land use and irrigation with respect to their impacts on summer temperatures
Landuse impacts in the middle latitudes are dominated by the cooling effect of grassland conversion, while the extensive deforestation in the United States Midwest does not show strong impacts on local or regional temperature
Summary
It is widely recognized that land use/land cover change (hereafter referred to as land use) affects the overlying atmosphere through land-atmosphere interactions, and modifies the local and broader-scale climate. Based on the CMIP5 simulations, many studies have been carried out to investigate the impacts of land use on climate (Brovkin et al, 2013; Kumar et al, 2013; Di Vittorio et al, 2014) and extreme events (Lejeune et al, 2017, 2018; Chen and Dirmeyer, 2018; Li et al, 2018). Impacts of Land Use/Irrigation in explaining the historical changes in temperature extremes over the regions with extensive land use (Chen and Dirmeyer, 2018). As an important agricultural practice to maintain adequate soil moisture for stable crop production, irrigation modifies the surface water budget, and affects the energy balance of the land surface, thereby altering the climate (Kueppers et al, 2007). Irrigation can change surface partitioning of available energy between sensible and latent heat fluxes by allowing more evapotranspiration through increased soil moisture and larger vegetation coverage, potentially lowering near-surface temperatures over the irrigated areas
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
