Atmospheric Modeling and Analysis Research
Integrated Tools for Scenario Discovery
Because climate change occurs over decades, scenarios are used to understand the impacts of policy decisions on a range of future outcomes. However, fully assessing air quality and climate change impacts of a given emission scenario requires extensive computational modeling and analysis. Tools that can rapidly inform decision-makers and stakeholders are a first-order need.
To meet this need, EPA is developing GLIMPSE — a framework for connecting atmospheric chemistry, radiative forcing, and energy-economy models to rapidly understand integrated air quality and climate change impacts of U.S. emission scenarios.
GLIMPSE stands for Geos-CHEM LIDORT Integrated with MARKAL for the Purpose of Scenario Exploration. Its four components are
- GEOS-Chem global chemical transport model to simulate the global impacts of US emissions
- LIDORT radiative transfer model to calculate the radiative forcing impacts from short-lived species such as black carbon (developed by Robert Spurr)
- Adjoint calculations of GEOS-Chem LIDORT, to explicitly attribute the contribution from US emission sources to global changes in radiative forcing
- EPA 9-Region MARKAL energy system model to discover the technologies, activities, and policy options that jointly achieve our air quality and climate change goals
In the first version of GLIMPSE, EPA will use the adjoint version of GEOS-Chem LIDORT model developed by Daven Henze at the University of Colorado. This model will calculate the change in sulfate and black carbon direct radiative forcing due to emissions from U.S. sources. These data will be used by MARKAL to find emission scenarios that achieve a given reduction in radiative forcing for minimal cost.
The key assumptions driving these emission scenarios will be further analyzed to find emission scenarios that robustly achieve reductions in radiative forcing despite uncertainties in future projections. Once a subset of robust emission scenarios is determined, they will be input into more complete global and regional climate models to fully quantify the impacts.
GLIMPSE data flow: GEOS-Chem LIDORT Adjoint model is used to attribute radiative forcing changes to US emission sectors. These data are used in conjunction with greenhouse gas emissions as constraints for the MARKAL model, which is in turn used to generate scenarios that meet these constraints