NOAA GFDL - Geophysical Fluid Dynamics LaboratoryGFDL - Geophysical Fluid Dynamics Laboratory

Kirsten’s land cover and land use change research

Why do models respond so differently to land cover change (LCC)?

  • Land use impacts the amount and partitioning of available energy at the earth’s surface.
  • Model response is dependent on weighting of various parameter changes.
  • In our land model LM2 (the predecessor to the current land model at GFDL), a change from forest to grassland leads to:

For a series of papers, we ran a number of experiments with different land cover distributions:

Strong local responses, weak remote responses:

  • Local responses to both perturbations are generally significant
    • Less Rnet, less evaporation, higher temperatures
    • Rainfall response not homogeneous
  • Remote responses do not pass field significance tests
  • Some globally and annually averaged fields do pass significance tests because of the strong local responses

  • In many regions, local responses to LCC are on par with response to a warm SST anomaly in the Pacific, and larger than the response to a warm SST anomaly in the North Atlantic or a warm global SST trend pattern

Conclusions:

  • LCC is important to include in climate-related experiments
  • Regional impacts can be statistically significant and as large as other well-known forcing factors
  • Impacts are especially important for water-balance considerations since fields like runoff, soil moisture, and evaporation can be so heavily affected
  • Remote responses do not pass field significance tests
    • Argues against LCC-induced teleconnections, even for large perturbations like complete tropical deforestation
  • Model limitations:
    • The experiments discussed here used LM2: only considered the biophysical impacts of LCC
    • Subsequent experiments will use LM3: improved biophysical representations and including the carbon cycle

Relevant papers:

Findell, Kirsten L., A J Pitman, M H England, and P J Pegion, June 2009: Regional and global impacts of land cover change and sea surface temperature anomalies. Journal of Climate, 22(12), doi:10.1175/2008JCLI2580.1

Findell, Kirsten L., Elena Shevliakova, P C D Milly, and Ronald J Stouffer, July 2007: Modeled impact of anthropogenic land cover change on climate. Journal of Climate, 20(14), doi:10.1175/JCLI4185.1.

Findell, Kirsten L., Thomas R Knutson, and P C D Milly, 2006: Weak simulated extratropical responses to complete tropical deforestation. Journal of Climate, 19(12), 2835-2850.