There is a new paper that further examines the role of land use change on the climate. It is
M.K. van der Molen, B.J.J.M. van den Hurk and W. Hazeleger (2011): A dampened land use change climate response towards the tropics. Climate Dynamics, open access, online first, DOI: 10.1007/s00382-011-1018-0.
The abstract reads
“In climate simulations we find a pronounced meridional (equator to pole) gradient of climate response to land cover change. Climate response approaches zero in the tropics, and increases towards the poles. The meridional gradient in climate response to land cover change results from damping feedbacks in the tropics, rather than from polar amplification. The main cause for the damping in the tropics is the decrease in cloud cover after deforestation, resulting in increased incoming radiation at the surface and a lower planetary albedo, both counteracting the increase in surface albedo with deforestation. In our simulations, deforestation was also associated with a decrease in sensible heat flux but not a clear signal in evaporation. Meridional differences in climate response have implications for attribution of observed climate change, as well as for climate change mitigation strategies.”
The conclusion reads
“Simulations with the EC-Earth climate model indicate a strong meridional gradient in climate response to land cover change: the climate response is nearly zero in the tropics and increases towards the NH mid-latitudes. Classical theory is that climate warming amplifies towards the poles, because of the snow-albedo feedback. However, in our simulations, the change in net radiation resembles the radiative forcing in the NH mid-latitudes, whereas it is much smaller in the tropics. This indicates that (net) damping feedbacks are present in the tropics, but not in the NH mid-latitudes. We show that in our model a decrease in cloud cover after deforestation is responsible for this ‘tropical damping’.
Distinguishing meridional differences in climate response to land cover change is important for attribution of climate change, and may have implications for the effectiveness of aforestation programs to mitigate climate change due to increasing CO2 concentrations. Simulations of the impact of land cover change on climate by different
climate models often provide contrasting results, as a consequence of defensible differences in model formulations. The climate response is a useful parameter for climate model intercomparisons, and we aim to contribute to such intercomparisons with this publication.”
One comment I have regarding this interesting paper is that, if “tropical damping” is due to a “decrease in cloud cover”, than what this paper calls a “climate response” is too narrowly defined. Nonetheless, this is an important new contribution to the recognition of land use/land cover change as a first order climate forcing.