Speaker: Henry Pollack is Emeritus Professor of Geophysics at the University of Michigan. He has served on many advisory panels for the National Science Foundation and the National Research Council, testified before the National Academy of Science, and provided briefings about climate change to Congress and the White House. His work on this topic is published widely in scientific journals. He is a scientific advisor to former Vice-President Al Gore’s Climate Reality Leadership Project and was a contributing author to the Nobel Prize-winning Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. He is an elected fellow of the American Geophysical Union, the Geological Society of America, and the American Association for the Advancement of Science. Pollack authored Uncertain Science … Uncertain World (Cambridge University Press 2003), a book aimed at a non-scientific audience, in which he discusses scientific uncertainty and the role it plays in the formulation of public policy. In a second book, A World Without Ice (Penguin 2009), he guides readers thtough the topic of global climate change as seen through the prism of ice. He received his Ph.D. in Geophysics from the University of Michigan in 1963.
The Earth’s climate has changed throughout history. Just in the last 650,000 years, there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes can be attributed to minute variations in the earth’s orbit that change the amount of solar energy our planet receives. The current warming trend is altogether different. There is a greater than 95 percent probability that this trend is the result, not of natural phenomena, but of human activity since the mid-20th century. The heat-trapping nature of carbon dioxide and other gases, i.e. their ability to affect the transfer of infrared energy through the atmosphere, was first demonstrated in the mid-19th century; ice cores drawn then as well as now from Greenland, Antarctica, and tropical mountain glaciers show that the earth’s climate responds to changes in greenhouse gas levels. Additional evidence to the same effect can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks: current warming is occurring roughly ten times faster than the average rate of ice-age-recovery warming. Anecdotal evidence of that is familiar to us all. Polar bear habitats in Alaska are threatened by receding sea ice. Migration of fish stocks due to warming ocean water threaten to decimate the livelihood of coastal communities in the Gulf of Maine. Persistent drought plagues the western United States. Hard evidence backs these perceptions up. Earth-orbiting satellites and other technological advances now enable scientists to collect many different types of information about our planet and its climate on a global scale. This body of data, collected over many years, reveals the signals of a changing climate. Our speaker will discuss the resulting challenge that confronts us.