The role of spatial scale and background climate in the latitudinal temperature response to deforestation

Abstract:

Previous modeling and observational studies have shown that the biophysical impact of deforestation is warming in the tropics and cooling in extra-tropics. In this study, we performed experiments with an earth system model to investigate how deforestation at various spatial scales affects ground temperature, with emphasis on the latitudinal temperature response and the underlining mechanisms. Results show that the latitudinal pattern of temperature response non-linearly depends on the spatial extent of deforestation and the fraction of vegetation change. Compared with regional deforestation, temperature change in global deforestation is greatly amplified in temperate and boreal regions, but is dampened in tropical region. Incremental forest removal fraction leads to increasingly larger cooling under higher removal fraction in temperate and boreal regions, while the temperature increase saturates in tropical region. The latitudinal and spatial patterns of the temperature response are mainly determined by two processes with competing temperature effects, i.e., decreases in absorbed shortwave radiation and in evapotranspiration (ET). These changes in surface energy balance reflect the important role of background climate on modifying the deforestation impact, because shortwave radiation and precipitation have intrinsic geographical distribution, which constrain the effects of biophysical changes and therefore lead to spatially varying temperature change. For example, wet (dry) climate favors larger (smaller) ET change, thus warming (cooling) is more likely to occur. Further analysis on the contribution of individual biophysical factor (albedo, roughness, and evapotranspiration efficiency) reveals that the latitudinal signature embodied in the temperature change likely arises from background climate conditions rather than from the initial biophysical perturbation.