Are We Capturing the True Impacts of Anthropogenic Land Cover Forcings in ESMs?

Abstract:

Simulation of anthropogenically induced land cover change impacts on climate has made significant progress over the last half century, starting with impacts of albedo and land cover change and evolving to include irrigation, urbanization and wood harvest carbon cycle impacts. However, many models still simulate these processes piece meal and the historical and Integrated Assessment Model (IAM) derived datasets used to drive these processes are not necessarily internally consistent in their implementation within Earth System Models. A further important question considers how anthropogenically driven feedbacks in the LULC-climate system will take place. In the future land cover change may be small given the lack of available arable land. However, land use intensification and political actions on energy consumption in urban systems may result in significant new indirect impacts on nutrient cycles and biogeophysical and biogeochemical processes.

This paper will review some of the land cover and land use (LCLU) processes simulated in ESMs and a review the sources of information used to define the geographical extent of LULC changes. One question to address is whether the current representation of these processes are adequate to simulate the totality of the anthropogenic climate impacts, given that in many cases there are differences in the intensity of land uses over space and time, and that a particular land cover class may actually encompass a wide variety of human activities. There also remain some land cover types/processes that are not well simulated in most models. For example the ill-defined land use class associated with pasture or grazing activities. Finally, it is important to consider which land cover types are most likely to change in the future. Perhaps more important than the spatial change is how processes within land cover types will change. For example, urban systems are likely to play a major role in determining LULC related influences on anthropogenic energy consumption and emissions. Any changes to how urban systems develop in the future will impact energy demand and constitute a human feedback, however, it potentially also impacts other land cover types. These processes need to be adequately linked in our simulations to ensure that we develop internally consistent scenario projections.