DOE scientists at Pacific Northwest National Laboratory demonstrated that a minimal representation of aerosol particles is suitable for estimating aerosol effects on the Earth’s energy balance in climate models. Aerosols affect the energy balance through scattering and absorbing sunlight and through their influence on cloud droplet number concentration. Climate simulations must account for all important radiative forcing mechanisms, including those due to human-caused aerosols. But because of the variety of sizes and compositions of aerosol particles, it is computationally too expensive to represent their full complexity in multi-century climate simulations. DOE scientists met this challenge by comparing simulations using the minimal representation of the aerosol and a more complex benchmark representation, showing that the minimal representation is accurate enough for climate change simulations and sufficiently inexpensive to enable multi-century simulations. This more efficient representation is being used in the Community Earth System Model to simulate future climate change for the Intergovernmental Panel on Climate Change.