Observational evidence of sensitivity of surface climate changes to land types and urbanization

Sensitivity of surface climate change to land types is investigated for the Northern Hemisphere by subtracting the reanalysis from the observed surface temperature (observation minus reanalysis). The basis of this approach is that while reanalysis represents the large-scale climate changes due to greenhouse gases and atmospheric circulation, it is less sensitive to regional surface processes associated with land types. OMR trends derived from two independent reanalyses (ERA40 and NNR) and two observation data sets (CRU and GHCN) show similar dependence upon land types, suggesting the attribution of OMRs to different land types is robust. OMR trends reveal 1) Warming over barren areas is larger than most other land types. 2) Urban areas show a large warming second only to barren areas. 3) Croplands with agricultural activity show a larger warming than natural broadleaf forests. The overall assessment indicates surface warming is larger for areas that are barren, anthropogenically developed, or covered with needle-leaf forests.