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IGSM response surface

Estimates of the mitigation costs associated with varying levels of emission reductions are generated through use of a response surface derived from runs of the Integrated Global System Model (IGSM). These runs of IGSM were published in a 2007 study undertaken as part of the U.S. Climate Change Science Program.

The response surface methodology used is only intended to approximate the results from the original IGSM model. In some cases the assumptions used in the original models differ from those in C-LEARN runs that generate inputs for the response surface, and this may lead to further inaccuracies. We believe, however, that the results of these models are are still accurate enough to be useful in providing a general sense of the likely impacts.

Overview #

Model name Integrated Global System Model (IGSM)

Brief description
IGSM combines a sophisticated earth system model with the Emissions Prediction and Policy Analysis (EPPA) model, a geographically disaggregated and sectorally complex integrated assessment model (IAM). The data on GDP under different emissions scenarios used in the response surfaces was generated by EPPA, so the remainder of this write-up focuses primarily on that part of IGSM.

Model developer(s)
EPPA developers include Z. Yang, Richard S. Eckaus,A. Denny Ellerman, Henry D. Jacoby, Mustafa H. Babiker, John M. Reilly, Monika Mayer, Ian Sue Wing, Robert C. Hyman, Sergey Paltsev, James McFarland, Marcus Sarofim, and Malcolm Asadoorian

Institutional affiliation of developer(s)
MIT Joint Program on the Science and Policy of Global Climate Change

Date created 1996

Date of most recent revision 2005

Model accessibility
EPPA is run in the lab, with results published in academic papers and reports issued by the Joint Center.


Key publications Leon E. Clarke, James A. Edmonds, Henry D. Jacoby, Hugh M. Pitcher, John M. Reilly, Richard G. Richels. 2007. Scenarios of Greenhouse Gas Emissions and Atmospheric Concentrations. U.S. Climate Change Science Program (CCSP) Synthesis and Assessment Product 2.1a.

Click here for "information that was collected from the modeling teams to support the development" of this CCSP report.

Click here for a complete list of publications issued in connection with this CCSP report, including public review comments and meeting minutes.

Model attributes #

Model type
EPPA is an integrated assessment model. The earth systems model to which is it linked in IGSM is a general circulation model (GCM).

Geographic scope Global

Geographic resolution
16 regions (with greater detail possible for analysis of policies in Europe)

Start date 2000

End date 2100

Time step 5 years

Data sources
Detailed information on the data sources used in EPPA can be found in Paltsev et al. 2005 and Babiker et al. 2001.

Approach for addressing risk/uncertainty
The develelopers of the EPPA model address uncertainty by running the model with differing values for key variables and assessing the degree of variation in the model runs that result.

Key modules and linkages between them
Detailed information on all of EPPA's modules and the linkages between them can be found in Paltsev et al. 2005 and Babiker et al. 2001.

The module used in the Climate CoLab is a response surface that shows the relationship between atmospheric concentration of CO2 and reduction in global gross domestic product in the emission stabilization scenarios when they are compared against the reference scenario. This response surface was based on runs of IGSM published in 2007 Clark et al. 2007. The steps undertaken in creating this response surface are outlined below in the section entitled "Variables and key assumptions."

Model structure

Variables and key assumptions #

Input variables
Global atmospheric concentration of carbon dioxide (CO2) at ten-year intervals between 2000 and 2100. (e.g. 2000, 2010, 2020, etc.)

Key assumptions

Atmos. Conc. CO2 Reference 750 ppm 650 ppm 550 ppm 450 ppm
2010 392 392 392 392 392
2020 419 415 414 410 402
2030 453 444 439 431 414
2040 494 478 468 452 423
2050 544 514 500 472 430
2060 603 554 531 488 435
2070 666 591 558 500 440
2080 733 624 581 511 445
2090 803 654 600 520 449
2100 875 677 614 526 451

% Reduct. Global GDP Reference 750 ppm 650 ppm 550 ppm 450 ppm
2010 0% 0.0% 0.0% 0.0% 0.0%
2020 0% 0.1% 0.2% 0.5% 2.1%
2030 0% 0.1% 0.3% 0.7% 3.0%
2040 0% 0.2% 0.4% 1.2% 4.1%
2050 0% 0.3% 0.6% 1.6% 5.4%
2060 0% 0.4% 0.9% 2.3% 6.7%
2070 0% 0.6% 1.3% 3.0% 8.2%
2080 0% 0.9% 1.8% 3.9% 10.1%
2090 0% 1.2% 2.3% 5.3% 12.6%
2100 0% 1.7% 3.1% 6.8% 16.1%

Output variables Reduction in global gross domestic product (GDP) at the stated level of global atmospheric concentration of CO2 at ten-year intervals between 2000 and 2100 (e.g. 2000, 2010, 2020, etc.).