Skip to main content

DAAC Home > Get Data > NASA Projects > Vegetation-Ecosystem Modeling and Analysis Project (VEMAP) > User guide
Get Data


The Vegetation/Ecosystem Modeling and Analysis Project (VEMAP) was a multi-institutional, international effort that addressed the response of biogeography and biogeochemistry to environmental variability in climate and other drivers in both space and time domains. The objectives of VEMAP were to study the intercomparison of biogeochemistry models and vegetation type distribution models (biogeography models) and determine their sensitivity to changing climate, elevated atmospheric carbon dioxide concentrations, and other sources of altered forcing.

Climate scenarios from eight climate change experiments are included in the data set. Seven of these experiments are from atmospheric general circulation model (GCM) 1xCO2 and 2xCO2 equilibrium runs. These GCMs were implemented with a simple "mixed-layer" ocean representation that includes ocean heat storage and vertical exchange of heat and moisture with the atmosphere, but omits or specifies (rather than calculates) horizontal ocean heat transport. The eighth scenario is from a limited-area nested regional climate model (RegCM) experiment for the U.S. which was supported by the Model Evaluation Consortium for Climate Assessment (MECCA). The CCC and GFDL R30 runs are among the high resolution GCM experiments reported in IPCC (1990). Changes in monthly mean temperature and relative humidity were represented as differences (2xCO2 climate value - 1xCO2 climate value) and those for monthly precipitation, solar radiation, vapor pressure, and horizontal wind speed as change ratios (2xCO2 climate value/1xCO2 climate value). GCM grid point change values were derived from archives at the National Center for Atmospheric Research (NCAR; Jenne 1992) and spatially interpolated to the 0.5 degree VEMAP grid. Wind speed changes are for the lowest model level. For GISS runs, we calculated winds from vector components and then determined the change ratio. Values from the 60-km RegCM grid were reprojected to the 0.5 degree grid. Vapor pressure (and relative humidity) were not available for the CCC run; relative humidity changes were not determined for the RegCM experiment. A key issue in the generation of altered climates based on climate model output is the strong possibility of physical inconsistencies in the new climates. Change ratios from the NCAR archive have an imposed upper limit of 5.0, providing some constraint on these changes. An exception is that the GISS wind speed change ratios do not have this limit imposed (most GISS wind speed change ratios were less than 5). For a discussion of the utility and limitations of using climate model experiment outputs for exploring ecological sensitivity to climate change, see Sulzman et al. (1995).

The 8 climate model experiments are:

A complete user's guide to the VEMAP Phase 1 database, which includes more information about this data set, can be found at

The ORNL DAAC maintains additional information associated with the VEMAP Project.

Data Citation:

Cite this data set as follows (data citation revised on Dec 18, 2002):

Kittel, T.G.F., N.A. Rosenbloom, T.H. Painter, D.S. Schimel, H.H. Fisher, A. Grimsdell, VEMAP Participants, C. Daly, and E.R. Hunt, Jr. 1998. VEMAP 1: U.S. Climate Change Scenarios Based on Models with Increased CO2. ORNL DAAC, Oak Ridge, Tennessee, USA.


Boer, G. J., N. A. McFarlane, and M. Lazare. 1992. Greenhouse gas- induced climate change simulated with the CCC second- generation general circulation model. J. Climate 5:1045-1077.

Giorgi, F., C. S. Brodeur, and G. T. Bates. 1994. Regional climate change scenarios over the United States produced with a nested regional climate model. J. Climate 7:375-399.

Hansen, J., A. Lacis, D. Rind, G. Russell, P. Stone, I. Fung, R. Ruedy, and J. Lerner. 1984. Climate sensitivity: Analysis of feedback mechanisms. Pp 130 - 163, in: Climate Processes and Climate Sensitivity. J.E. Hansen and T. Takahashi (eds). Geophysical Monograph 29. American Geophysical Union, Washington, D.C.

IPCC. 1990. Climate Change: The IPCC Scientific Assessment. J. T. Houghton, G. J. Jenkins, and J. J. Ephraums (eds.). Intergovernmental Panel on Climate Change. Cambridge University Press, New York. 365 pp.

Jenne, R. L. 1992. Climate model description and impact on terrestrial climate. Pp. 145 - 164, in: Global Climate Change: Implications, Challenges and Mitigation Measures. S. K. Majumdar, L. S. Kalkstein, B. Yarnal, E. W. Miller, and L. M. Rosenfeld (eds.). Pennsylvania Academy of Science.

Kittel, T. G. F., N. A. Rosenbloom, T. H. Painter, D. S. Schimel, and VEMAP Modeling Participants. 1995. The VEMAP integrated database for modeling United States ecosystem/vegetation sensitivity to climate change. Journal of Biogeography 22:857-862.

Manabe, S., and Wetherald, R. T. 1990. [Reported in: Mitchell, J.F.B., S. Manabe, V. Meleshko, T. Tokioka. Equilibrium Climate Change and its Implications for the Future. Pp. 131- 172, in: Climate Change: The IPCC Scientific Assessment. Houghton, J. T., G. J. Jenkins, and J. J. Ephraums (eds.). Cambridge University Press, Cambridge, UK.]

Marks, D. 1990. The sensitivity of potential evapotranspiration to climate change over the continental United States. Pp. IV- 1 - IV-31, in: Biospheric Feedbacks to Climate Change: The Sensitivity of Regional Trace Gas Emissions, Evapotranspiration, and Energy Balance to Vegetation Redistribution. H. Gucinski, D. Marks, and D.P. Turner (eds.). EPA/600/3-90/078. U.S. Environmental Protection Agency, Corvallis, OR.

Marks, D., and J. Dozier. 1992. Climate and energy exchange at the snow surface in the alpine region of the Sierra Nevada: 2. Snow cover energy balance. Water Resources Research 28:3043-3054.

NFNOC (Navy Fleet Numeric Oceanographic Center). 1985. 10-minute Global Elevation Terrain, and Surface Characteristics. (Re- processed by NCAR and NGDC). NOAA National Geophysical Data Center. Digital data set.

Richardson, C. W. 1981. Stochastic simulation of daily precipitation, temperature and solar radiation. Water Resources Research 17:182-190.

Schlesinger, M. E., and Z. C. Zhao. 1989. Seasonal climate changes induced by doubled CO2 as simulated by the OSU atmospheric GCM- mixed layer ocean model. J. Climate 2:459-495.

Sulzman, E.W., K.A. Poiani, and T.G.F. Kittel (1995) Modeling human-induced climatic change: A summary for environmental managers. Environmental Management 19:197-224.

Thompson, S.L. and D. Pollard (1995a) A global climate model (GENESIS) with a land-surface-transfer scheme (LSX). Part 1: Present-day climate. J. Climate 8:732-761.

Thompson, S.L. and D. Pollard (1995b) A global climate model (GENESIS) with a land-surface-transfer scheme (LSX). Part 2: CO2 sensitivity. J. Climate 8:1104-1121.

VEMAP Members (1995) Vegetation/Ecosystem Modeling and Analysis Project: Comparing biogeography and biogeochemistry models in a continental-scale study of terrestrial ecosystem responses to climate change and CO2 doubling. Global Biogeochem. Cycles 9:407-437.

Wetherald, R.T., and S. Manabe (1990) [Reported in: Cubasch, U., and R.D. Cess. Processes and Modeling. Pp. 69-91, in: Climate Change: The IPCC Scientific Assessment. Houghton, J.T., G.J. Jenkins, and J.J. Ephraums (eds). Cambridge University Press, Cambridge, UK.]

Wilson, C.A., and J.F.B. Mitchell (1987) A doubled CO2 climate sensitivity experiment with a global climate model including a simple ocean. J. Geophys. Res. 92 (D11):13,315-13,343.

Document Information:

Document Review Date: