Colloquium: Dr. Ralph Kahn (NASA/ GSFC)

TITLE: A Planetary Perspective on Aerosols & Climate ABSTRACT: The planetary scale view offers useful perspectives on important aspects of climate and climate change on Earth and Mars. This presentation begins with two constraints on the climate history of Mars. One relates to the long-term evolution of the carbon dioxide atmosphere as deduced from the current atmospheric pressure as compared to the likely original endowment of CO2. The second compares the periodicity of climate changes indicated by Mars polar layered terrain deposits to the periodicity of climate forcing due to oscillations of the Mars orbit. These two scenarios are compared to the corresponding carbon cycle and periodicity of major ice ages on Earth, illustrating the power of comparative climatology for climate study. The presentation then focuses more specifically on Earth, describing what we know about aerosols in our planet’s atmosphere, and the role airborne particles play in modulating Earth’s climate. Here the strengths and limitations of current, global-scale remote sensing are covered, and the prospects for addressing uncertainties through a combination of satellite and suborbital observations, used to constrain global climate modeling.