Published: March 17, 2009

University of Colorado at Boulder geological sciences Professor Gifford Miller has been elected a fellow of the American Geophysical Union, an international organization made up of about 45,000 member scientists from more than 130 countries.

Miller, also a fellow of CU-Boulder's Institute of Arctic and Alpine Research, was honored "for his pioneering work in dating methods as well as his insights into the Quaternary climates and the role of humans in ecological change." The Quaternary period -- the last 2.6 million years -- includes the Pleistocene and Holocene epochs.

Miller was one of only 38 AGU Fellows elected from the United States in 2009 for their outstanding science and community contributions. An additional 16 AGU fellows were elected from outside the United States. The AGU Fellow awards -- which annually recognize members who have made outstanding science and community contributions -- are conferred on no more than 0.1 percent of AGU members in any given year.

Miller's primary research involves studying the geological record to evaluate the range of natural climate variability as a way to understand how Earth responds to climate changes as the result of ice ages. He has combined field observations with geochronological dating techniques in his research, with emphasis on the past 150,000 years -- one complete glacial-interglacial cycle of Earth.

His interests include the timing and mechanisms of ice-sheet growth and decay in the Canadian and European Arctic and the interactions of ice sheets, oceans and the atmosphere during the last deglaciation. Miller, who founded and directs CU-Boulder's Center for Geochronological Research, also has developed new dating tools involving carbonate fossils as a way to date geological and archaeological events.

Miller and his colleagues have assembled high-resolution records of environmental change for the Arctic over the past 20,000 years based on evidence preserved in lake-bed sediments. A 2008 study led by Miller showed that ice caps on the northern plateau of Baffin Island in the Canadian Arctic have shrunk by more than 50 percent in the last half century as a result of warming temperatures, and are expected to disappear by the middle of the century.

The last time the region was warm enough to melt ice caps was more than 1,500 years ago, when there was more solar energy in the summers than today but fewer greenhouse gases, Miller said.

Miller also studies prehistoric monsoon cycles in Australia, as well as the earliest immigration of humans to the continent and their impact on climate, regional vegetation and the extinction of megafuana. Giant Australian animals that went extinct in the past 50,000 years include Volkswagen sized tortoises, hippo-sized wombats, 1,300-pound lizards and 200-pound birds known as Genyornis newtoni.

By analyzing fossil eggshells of extinct emus and Genyornis inhabiting Australia tens of thousands of years ago and determining the composition of their vegetarian diets through carbon isotope analysis, Miller showed early human immigrants likely altered the continent's interior with fire. Such burning may have triggered the failure of the annual Australian monsoon some 12,000 years ago, shifting the landscape from a mosaic of trees, shrubs and grasses to the desert scrub evident today.