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Nature 479, 384 - 387 (7373)
Published online: 2011-11-17; | doi:10.1038/nature10588

Article: Observed increase in local cooling effect of deforestation at higher latitudes

  1. #33957
    Date:
    2011-12-13 03:26:45 PM
    Ken Caldeira said:

    Expecting cooling from deforestation

    Lee et al. (Nature 479, 384?387; 2011) concluded that deforestation in the mid- to high-latitudes caused less of a cooling than what might be expected based on idealized global climate simulations. Here, we offer two hypotheses that might explain their conclusion.

    First, the validity of the space-for-time substitution depends on the extent of land cover change. In highly idealized deforestation scenarios, deforestation occurs over a wide region and cooling occurs throughout and beyond that region, even in model grid cells that did not undergo land-cover change (Claussen et al., Geophys. Res. Lett. 28, 1011-1014; 2001; Bala et al., Proc. Natl. Acad. Sci. 104, 6550?6555; 2007). Therefore, the temperature difference between this area and areas that did not undergo land-cover change is smaller in magnitude than is the temperature change at the area of land cover change between before and after the transition.

    Second, lands that were converted historically from forest to agricultural uses tended to be less snowy (and more carbon-rich) than typical forested land at the same latitude; farmers? past preferences would thus lead to a smaller cooling influence of historical deforestation in these areas (Pongratz et al., Geophys. Res. Lett. 38, L15701; 2011) than predicted by idealized modeling studies.

    Thus, we would expect real world observations such as those described by Lee et al. (2011) to show less of a cooling effect than predicted by idealized global climate simulations.

    Ken Caldeira and Julia Pongratz
    Carnegie Institution Dept. of Global Ecology, Stanford, California, USA. kcaldeira@carnegie.stanford.edu

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