Deforestation of the Amazon rainforest is expected to cause the temperature in the region to rise and rainfall patterns to shift. Exactly how and how much the regional climate will change in the face of rampant deforestation, however, is a matter of considerable ongoing investigation. With their research, Lorenz and Pitman add a new piece to the puzzle by showing that the strength of land-atmosphere coupling in a given model influences how it represents deforestation’s effects.
Not all ecosystems affect rainfall generation and atmospheric circulation patterns in the same way. Different land surfaces have different roughnesses, albedos, and effects on atmospheric convection and turbulence. Likewise, changes to different ecosystems will resonate differently throughout the climate system. The effect of a tree cut down in a grassland is different from that of a tree cut down in a forest.
The land-atmosphere coupling strength is a numerical representation of the degree to which a small change in land surface properties affects the behavior of the atmosphere. Land-atmosphere coupling strengths are set by a given model’s construction and can vary seasonally, temporally, and regionally.
Although researchers have previously investigated the effect of models’ land-atmosphere coupling strengths on their projections, none of them have done so with an emphasis on deforestation and land use change. In their research, the authors found that the coupling strength does have an effect on how deforestation translates into projected rainfall and temperature changes. That every model has a slightly different setting for the land-atmosphere coupling strength suggests that no one model can be used to calculate the effect of deforestation or land use change on these climate variables.
The key to building better estimates of deforestation’s effects, the authors suggest, will be gaining a deeper understanding of the true land-atmosphere coupling strength in each model and using multimodel ensembles to help account for land-atmosphere coupling uncertainty. (Geophysical Research Letters, doi:10.1002/2014GL061017, 2014)
—Colin Schultz, Writer
Citation: Schultz, C. (2014), Uncertainty in deforestation’s effects on Amazonian climate, Eos Trans. AGU, 95(49), 472, doi:10.1002/2014EO490014.