Thanks to Geoff Smith for alerting us to this important new research paper on the role of land surface processes within the climate system. The paper is
Davin, E. L., N. de Noblet-Ducoudré, and P. Friedlingstein (2007), Impact of land cover change on surface climate: Relevance of the radiative forcing concept, Geophys. Res. Lett., 34, L13702, doi:10.1029/2007GL029678.
The abstract reads
“We use the IPSL climate model to investigate biophysical impacts of Anthropogenic Land Cover Change (ALCC) on surface climate. Including both the changes in surface albedo and evapotranspiration, we find that ALCC represents a radiative forcing of −0.29 W/m2 from 1860 to 1992 and of −0.7 W/m2 from 1992 to 2100. The simulated surface temperature response to ALCC indicates a historical cooling of 0.05 K and an additional cooling due to future changes of 0.14 K, which is consistent with the sign of the radiative forcing. However, this cooling is substantially lower than the one we would have obtained if it was caused by a radiatively equivalent change in CO2 concentration. These results thus question the relevance of the radiative forcing framework in the context of land use change, since the radiative forcing due to ALCC may not be comparable to the one exerted by other anthropogenic perturbations. ”
Indeed, the radiative forcing due to ALCC is not directly comparable to the global average radiative forcing of the well mixed greenhouse gases (as was discussed yesterday on Climate Science for other climate forcings). This paper illustrates why we need to move beyond defining “Climate Sensitivity” as a global average metric.
“Climate sensitivity” should be a matrix of metrics that are determined by stakeholders who define what are the important climate quantities with respect to their specific resource (such as local growing degree days, summer rainfall, etc). Then the challenge to the climate modeling community is whether they can skillfully predict changes in these metrics in the coming years and decades.