Our Changing Atmosphere
Wednesday, October 25, 2006
Lecture 4:30 p.m.
Technological Institute, Lecture Room 2
2145 Sheridan Road, Evanston, Illinois
Reception to follow in the Jerome B. Cohen Commons
Free parking is available after 4 p.m. in the F parking lot on the west side of Sheridan Road across from the Technological Institute.

Aerosols and Climate
Thursday, October 26, 2006
Lecture 11 a.m.
Technological Institute, Room L361
2145 Sheridan Road, Evanston, Illinois
Refreshments preceding the lecture at 10:45 a.m. in Room L324

Our Changing Atmosphere

Over the last century humans have embarked on an environmental experiment of unprecedented proportions. As a result of human activity during this time, atmospheric levels of trace gases have increased markedly. Manifestations include stratospheric ozone depletion, tropospheric air pollution, and global climate change. The atmosphere is an enormous chemical reactor with its energy supplied by the sun. Gases and particles emitted at the earth’s surface interact through exquisitely complex chemistry to yield a bewildering array of products, some of which are injurious to human health, and others of which have climatic impacts. This lecture reviews the essential elements and status of stratospheric ozone depletion, tropospheric pollution, and global climate change.

Aerosols and Climate

The earth’s temperature results from a balance between incoming shortwave radiation from the sun and outgoing long-wave radiation from the earth. Any factor that perturbs this balance has the potential to change the earth’s climate. The buildup of greenhouse gases, such as CO2, leads to increased trapping of the earth’s radiation and the tendency of the earth to become warmer. Particles in the air — so-called aerosols — are ubiquitous in and essential to our atmosphere. For example, they are the sites for condensation of water vapor to form clouds. Atmospheric particles interact with radiation and influence the earth’s cloudiness, effects that also perturb the earth’s energy balance. This lecture examines the mechanisms by which aerosols influence climate and the extent to which these mechanisms are important contributors to climate change.