Written by Roger Pielke Sr.
November 22, 2008
Roger Pielke Sr.
Originally posted on August 5, 2005.
As recognized by the National Research Council in 2005, land-use/land-cover change is a first-order climate forcing. However, its role as a regional and global climate influence is not widely recognized, except as it effects the atmospheric concentration of carbon dioxide and the global average surface albedo. In the summary figure from the IPCC Statement for Policymakers (see Figure ES-2 here), in terms of the global mean radiative forcing, only albedo effects of land use/land cover change are identified.
However, numerous studies have shown that the effect of land-cover/land-use change is to alter temperatures and precipitation in regions where the change occurs, as well as weather globally through teleconnections (see, for example, The influence of land-use change and landscape dynamics on the climate system: relevance to climate-change policy beyond the radiative effect of greenhouse gases and The climatic impacts of land-surface change and carbon management, and the implications for climate change mitigation policy).
The reason for this influence is described in a presentation I gave entitled "Land-Use/Land-Cover Change as a Major Climate Forcing: Evidence and Consequences for Climate Research." In the talk, I asked the question "why should landscape effects, which cover only a fraction of the Earth's surface, have global circulation effects?" The answer can be summarized as follows:
We should, therefore expect global climate effects from land-use/land-cover change. The next IPCC needs to focus more on this first-order climate forcing than they have in the past. The question of searching for a "discernable effect on the climate system" misses the obvious in that we have been altering regional and global climate by land-use/land-cover change for decades. The goal of "preventing dangerous anthropogenic interference with the climate system" (from the UN Framework Convention on Climate Change, article 2, 1999), by focusing on CO2, has overlooked the first order climate forcing of land-use/land-cover change in altering the surface heat and water vapor fluxes.