Forcings in GISS Climate Model

Land Use/Land Cover

Conversion of Natural Vegetation to Cropland and Pasture

The dominant mode of land-cover change over the last millennium is the replacement of natural vegetation with crops and pasture, and occasionally vice versa. We have used a number of estimates of these changes from Pongratz et al. (2008), Kaplan et al. (2010) and the HYDE3.1 database (Klein Goldewijk et al., 2011), which can be downloaded from:

Prior to CMIP5, we used data from Ramankutty and Foley (1999).


The use of transient irrigation estimates as a climate forcing in the GISS GCM was pioneered by Puma and Cook (2010) and Cook et al (2015).

Irrigation changes over the 20th Century

The gridded monthly data for irrigation (mm/day) from 1848 to 2002 are available here (netCDF).


Please address inquiries about these data to Dr. Benjamin Cook.


Cook, B.I., S.P. Shukla, M.J. Puma, and L. Nazarenko, 2015: Irrigation as an historical climate forcing. Clim. Dyn., 44, 1715-1730, doi:10.1007/s00382-014-2204-7.

Kaplan, J. O., Krumhardt, K. M., Ellis, E. C., Ruddiman, W. F., Lemmen, C., and Klein Goldewijk, K., 2010: Holocene carbon emissions as a result of anthropogenic land cover change, The Holocene, 21, 775-791, doi:10.1177/0959683610386983.

Klein Goldewijk, K., Beusen, A., van Drecht, G., and de Vos, M., 2011: The HYDE 3.1 spatially explicit database of human-induced global land-use change over the past 12,000 years, Global Ecol. Biogeogr., 20, 73-86, doi:10.1111/j.1466-8238.2010.00587.x.

Pongratz, J., C. H. Reick, T. Raddatz, and M. Claussen, 2008: A reconstruction of global agricultural areas and land cover for the last millennium. Glob. Biogeochem. Cycles, 22, no. 3, GB3018. doi:10.1029/2007GB003153.

Puma, M.J., and B.I. Cook, 2010: Effects of irrigation on global climate during the 20th century. J. Geophys. Res., ,115, D16120, doi:10.1029/2010JD014122.

Ramankutty, N. and J. A. Foley, 1999: Estimating historical changes in global land cover: Croplands from 1700 to 1992. Glob. Biogeochem. Cycles, 1, 997–1027, doi:10.1029/1999GB900046.

Note: PDF documents require the free Adobe Reader or compatible viewing software to be viewed.

This page was written by Dr. Gavin Schmidt.

+ Return to Model Forcings Homepage