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Dust Aerosol Important for Snowball Earth Deglaciation DORIAN S. ABBOT

Summary: Dust Aerosol Important for Snowball Earth Deglaciation
Department of Geophysical Sciences, University of Chicago, Chicago, Illinois
Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts
(Manuscript received 11 August 2009, in final form 28 December 2009)
Most previous global climate model simulations could only produce the termination of Snowball Earth
episodes at CO2 partial pressures of several tenths of a bar, which is roughly an order of magnitude higher than
recent estimates of CO2 levels during and shortly after Snowball events. These simulations have neglected the
impact of dust aerosols on radiative transfer, which is an assumption of potentially grave importance. In this
paper it is argued, using the Dust Entrainment and Deposition (DEAD) box model driven by GCM results,
that atmospheric dust aerosol concentrations may have been one to two orders of magnitude higher during
a Snowball Earth event than today. It is furthermore asserted on the basis of calculations using NCAR's Single
Column Atmospheric Model (SCAM)--a radiative­convective model with sophisticated aerosol, cloud, and
radiative parameterizations--that when the surface albedo is high, such increases in dust aerosol loading
can produce several times more surface warming than an increase in the partial pressure of CO2 from 1024
bar. Therefore the conclusion is reached that including dust aerosols in simulations may reconcile the


Source: Abbot, Dorian Schuyler - Department of Geophysical Sciences, University of Chicago
Halevy, Itay - Department of Environmental Sciences and Energy Research, Weizmann Institute of Science
Halevy, Itay - Division of Geological and Planetary Sciences, California Institute of Technology


Collections: Geosciences; Physics