Sensitivity of Aerosol Forcing to Observed Variation in Aerosol Properties at Bondville

IPCC (1995) temperature change predictions used a single value and considered only scattering.

Forcing per unit optical depth (W m-2)

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• Given the observed variation in aerosol optical properties over the past 15 months at Bondville…what would the corresponding variation in TOA forcing be?

• Forcing per unit optical depth on x-axis, frequency that value was observed on the y

• If considering scattering aerosol only (w0 = 1.0), the peak in the frequency distribution represents a net TOA forcing of ~ -32 W m-2 per unit AOD

• If observed absorption is considered, the distribution broadens considerably and the peak shifts to the right (lessens the negative TOA forcing)