|by Cynthia Rosenzweig and Ana Iglesias
Note: This data set has now been superseded by a new data set on the effects of climate change on global food production under SRES emissions and socio-economic scenarios produced by the same authors. Users are recommended to use the new data instead. SEDAC is maintaining this web site for reference purposes.
1. The Climate Change Scenarios
Scenarios of future climate were derived from the output of general circulation
models (GCMs) driven by anticipated changes in atmospheric composition
(e.g., CO2 emissions, sulphate aerosols,
etc). GCMs are mathematical models that describe the processes
that are known to occur in the earth's climate system and their possible
interactions. Such models are used to forecast the trend of climate over
the coming decades. Their results are still tentative and should not be
accepted uncritically. However, we should examine the implications of
their predictions, while continuing to look for the emerging empirical
evidence of changing climate. A list of the major GCMs is available at
Examples of IPCC Carbon-Dioxide Concentrations Scenarios and Associated Temperature Changes
Source: Intergovernmental Panel on Climate Change (1995)
Two kinds of climate change scenarios were utilized: equilibrium scenarios and transient scenarios. The former are based on the assumption of a doubling of atmospheric CO2 concentrations from pre-industrial levels (i.e., from 227 ppm to 555 ppm). When that will happen no one can be sure, so equilibrium scenarios are not tied to specific future dates, but rather simply reflect the point at which CO2 is doubled in the atmosphere. The equilibrium scenarios for three major GCMs were utilized in this study: The Goddard Institute for Space Studies (GISS), the Geophysical Fluid Dynamics Laboratory (GFDL), and the UK Meteorological Office (UKMO).
Transient scenarios, by contrast, are time dependent. They tell you what will happen at some date in the future based on assumptions contained within the model. The transient scenarios considered were derived from simulations with the Hadley Centre for Climate Prediction and Research's Climate Model 2 (HadCM2) and Climate Model 3 (HadCM3) of the UK Met Office. The studies analyzed five sets of scenarios derived from the HadCM2 and HadCM3 models with different forcing emmission scenarios.
Future agricultural scenarios were the combination of the climate change, crop response scenarios (i.e., physiological response to elevated CO2 ), and farmers' adaptive responses. Thus, the crop simulations were based on some combination of the following assumptions:
Climate change scenarios [8 to choose from]
For more information on these agricultural scenarios, please see the
Methodology section of this web site.
The following box summarizes all the combinations utilized to generate crop yield estimates. The scenarios have been numbered in order to make them easier to identify.
Scenarios Utilized for the Crop-Climate Modeling