Crop-climate model scenarios

Potential Impacts of Climate Change on World Food Supply

Data Sets from a Major Crop Modeling Study

by Cynthia Rosenzweig and Ana Iglesias

The Scenarios

Note: This data set has now been superseded by a new data set on the effects of climate change on global food production under SRES emissions and socio-economic scenarios produced by the same authors.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 the IPCC web site.

Examples of IPCC Carbon-Dioxide Concentrations Scenarios and Associated Temperature Changes

Tables: 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.

HadCM2(97)gg: Ensemble-mean for the HadCM2 model forced with greenhouse gas concentrations from the IS95a emission scenario. [note: this scenario has been removed from the query tool owing to problems with the crop response data (January 2007)]
HadCM2(97)gs: Same as the one above, but it includes the simulation of the effects of sulphate aerosols, which are expected to attenuate the warming influence of increased CO₂ concentrations. [note: this scenario has been removed from the query tool owing to problems with the crop response data (January 2007)]
HadCM3-A: A variation of the HadCM3 model forced with greenhouse gas concentrations derived form the IS95a emission scenario.
HadCM2-S550: HadCM2 model forced with a CO₂ stabilization scenario (clean scenario). This simulation assumes a major policy effort to reduce greenhouse gas emissions, with stabilization at 550 ppm in 2170.
HadCM2-S750: HadCM2 model forced with a CO₂ stabilization scenario (less clean scenario). This simulation assumes a more modest policy effort to bring about stabilization of CO₂ emissions to 750 ppm in 2170.

2. The Agricultural 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] +
                    CO₂ effects on crop growth [either with or without] +
                                    Adaptation [none, level 1 and level 2]

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

Equilibrium Scenarios

GISS#1 = Equilibrium scenario, No CO₂ effects, No adaptation
GISS#2 = Equilibrium scenario, CO₂ effects (555 ppm), No adaptation
GISS#3 = Equilibrium scenario, CO₂ effects (555 ppm), Level 1 adaptation
GISS#4 = Equilibrium scenario, CO₂ effects (555 ppm), Level 2 adaptation

GFDL#1 = Equilibrium scenario, No CO₂ effects, No adaptation
GFDL#2 = Equilibrium scenario, CO₂ effects (555 ppm), No adaptation
GFDL#3 = Equilibrium scenario, CO₂ effects (555 ppm), Level 1 adaptation
GFDL#4 = Equilibrium scenario, CO₂ effects (555 ppm), Level 2 adaptation

UKMO#1 = Equilibrium scenario, No CO₂ effects, No adaptation
UKMO#2 = Equilibrium scenario, CO₂ effects (555 ppm), No adaptation
UKMO#3 = Equilibrium scenario, CO₂ effects (555 ppm), Level 1 adaptation
UKMO#4 = Equilibrium scenario, CO₂ effects (555 ppm), Level 2 adaptation

Transient Scenarios

[Note: the following set of HadCM2(97)gg scenarios has been removed from the query tool owing to problems with the crop response data (crop yields for CO2 effects scenarios were lower than the no CO2 effects runs - contrary to what is expected)]

HadCM2(97)gg#1 = Decade 2020s, CO₂ effects (441 ppm), Level 1 adaptation adaptation
HadCM2(97)gg#2 = Decade 2020s, No CO₂ effects, Level 1 adaptation
HadCM2(97)gg#3 = Decade 2050s, CO₂ effects (565 ppm), Level 1 adaptation
HadCM2(97)gg#4 = Decade 2050s, No CO₂ effects, Level 1 adaptation adaptation
HadCM2(97)gg#5 = Decade 2080s, CO₂ effects (731 ppm), Level 1 adaptation
HadCM2(97)gg#6 = Decade 2080s, No CO₂ effects, Level 1 adaptation

[Note: the following set of HadCM2(97)gs scenarios has been removed from the query tool owing to problems with the crop response data (crop yields for CO2 effects scenarios were lower than the no CO2 effects runs - contrary to what is expected)]

HadCM2(97)gs#1 = Decade 2020s, CO₂ effects (441 ppm), Level 1 adaptation adaptation
HadCM2(97)gs#2 = Decade 2020s, No CO₂ effects, Level 1 adaptation
HadCM2(97)gs#3 = Decade 2050s, CO₂ effects (565 ppm), Level 1 adaptation
HadCM2(97)gs#4 = Decade 2050s, No CO₂ effects, Level 1 adaptation adaptation
HadCM2(97)gs#5 = Decade 2080s, CO₂ effects (731 ppm), Level 1 adaptation
HadCM2(97)gs#6 = Decade 2080s, No CO₂ effects, Level 1 adaptation

HadCM3-A#1 = Decade 2020s, No CO₂ effects, Level 1 adaptation
HadCM3-A#2 = Decade 2020s, CO₂ effects (475 ppm), Level 1 adaptation
HadCM3-A#3 = Decade 2050s, No CO₂ effects, Level 1 adaptation
HadCM3-A#4 = Decade 2050s, CO₂ effects (574 ppm), Level 1 adaptation
HadCM3-A#5 = Decade 2080s, No CO₂ effects, Level 1 adaptation
HadCM3-A#6 = Decade 2080s, CO₂ effects (712 ppm), Level 1 adaptation

HadCM2-S550#1 = Decade 2020s, No CO₂ effects, Level 1 adaptation
HadCM2-S550#2 = Decade 2020s, CO₂ effects (410 ppm), Level 1 adaptation
HadCM2-S550#3 = Decade 2050s, No CO₂ effects, Level 1 adaptation
HadCM2-S550#4 = Decade 2050s, CO₂ effects (458 ppm), Level 1 adaptation
HadCM2-S550#5 = Decade 2080s, No CO₂ effects, Level 1 adaptation
HadCM2-S550#6 = Decade 2080s, CO₂ effects (498 ppm), Level 1 adaptation
HadCM2-S550#7 = Decade 2110s, No CO₂ effects, Level 1 adaptation
HadCM2-S550#8 = Decade 2110s, CO₂ effects (530 ppm), Level 1 adaptation

HadCM2-S750#1 = Decade 2020s, No CO₂ effects, Level 1 adaptation
HadCM2-S750#2 = Decade 2020s, CO₂ effects (424 ppm), Level 1 adaptation
HadCM2-S750#3 = Decade 2050s, No CO₂ effects, Level 1 adaptation
HadCM2-S750#4 = Decade 2050s, CO₂ effects (501 ppm), Level 1 adaptation
HadCM2-S750#5 = Decade 2080s, No CO₂ effects, Level 1 adaptation
HadCM2-S750#6 = Decade 2080s, CO₂ effects (577 ppm), Level 1 adaptation
HadCM2-S750#7 = Decade 2110s, No CO₂ effects, Level 1 adaptation
HadCM2-S750#8 = Decade 2110s, CO₂ effects (643 ppm), Level 1 adaptation

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