Vegetation feedback under future global warming

Abstract

It has been well documented that vegetation plays an important role in the climate system. However, vegetation is typically kept constant when climate models are used to project anthropogenic climate change under a range of emission scenarios in the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios. Here, an atmospheric general circulation model, and an asynchronously coupled system of an atmospheric and an equilibrium terrestrial biosphere model are forced by monthly sea surface temperature and sea ice extent for the periods 2051–2060 and 2090–2098 as projected with 17 atmosphere–ocean general circulation models participating in the IPCC Fourth Assessment Report, and by appropriate atmospheric carbon dioxide concentrations under the A2 emission scenario. The effects of vegetation feedback under future global warming are then investigated. It is found that the simulated composition and distribution of vegetation during 2051–2060 (2090–2098) differ greatly from the present, and global vegetation tends to become denser as expressed by a 21% (36%) increase in global mean leaf area index, which is most pronounced at the middle and high northern latitudes. Vegetation feedback has little effect on globally averaged surface temperature. On a regional scale, however, it induces statistically significant changes in surface temperature, in particular over most parts of continental Eurasia east of about 60°E where annual surface temperature is expected to increase by 0.1–1.0 K, with an average of about 0.4 K for each future period. These changes can mostly be explained by changes in surface albedo resulting from vegetation changes in the context of future global warming.