Newswise — Two scientists who found warning signs of climate change in the upper atmosphere and in the deepest ice sheets will deliver the 2009 Tyler Prize lectures at USC on April 23.  Richard Alley, professor of geosciences at Penn State University, and Veerabhadran (Ram) Ramanathan, professor of atmospheric and climate sciences in the Scripps Institution of Oceanography at the University of California, San Diego, will deliver public lectures on Thursday, April 23, at 2 p.m. at the Davidson Conference Center of the University of Southern California, which administers the prize. On Friday, April 24, at 7 p.m., the Tyler Prize Executive Committee and the international environmental community will honor the recipients at a banquet and ceremony at the Four Seasons Hotel in Beverly Hills, and present them with a shared $200,000 cash prize and gold medals. The prize committee recognized the two "for their scientific contributions that advanced understanding of how human activities influence global climate, and alter oceanic, glacial and atmospheric phenomena in ways that adversely affect planet Earth."  Alley is widely credited with showing that Earth has experienced abrupt climate change in the past, and likely will again. He based his work on a meticulous study of ice cores from Greenland and West Antarctica. Up to two miles thick, the ice sheets contain a unique record of Earth's climate history. "Among climate scientists he is a recognized as an outstanding example of a superlative researcher who has found a way to balance his passion for discovery with his duty to inform nonscientists of the crises that are looming," geophysicist Garry Clarke of the University of British Columbia wrote in support of Alley's nomination. "His wonderful book 'The Two-Mile Time Machine' (on the climate record from Greenland ice cores and its implications for humankind) combines good science with a serious message and succeeds, equally, with novices and experts."  One of the world's leading atmospheric scientists, Ramanathan was the first to show that ozone-depleting aerosols could aggravate the greenhouse effect. In 1980, he correctly predicted that global warming from carbon dioxide would be detectable by the year 2000.  More recently, Ramanathan showed that South Asian "brown clouds" caused by the burning of fossil fuels could lower ocean temperatures, slowing down monsoon circulation and reducing seasonal rainfall. In a pioneering study with agricultural economists, he linked the phenomenon to a significant decrease in the Indian rice harvest. Ramanathan also showed that black carbon particles in brown clouds absorb far more solar radiation than previously thought, contributing to the warming of the upper atmosphere. "I consider currently Dr. Ramanathan to be one of the greatest, if not the greatest, climate researcher," wrote Paul Crutzen, winner of the 1995 Nobel Prize in Chemistry, in support of Ramanathan's nomination.  Ramanathan and Alley served as authors on the U.N. Intergovernmental Panel on Climate Change, whose members shared the 2007 Nobel Peace Prize with former Vice President Al Gore. ABOUT THE TYLER PRIZE The annual Tyler Prize for Environmental Achievement is one of the premier awards for environmental science, energy and environmental health.  It was established by the late John and Alice Tyler in 1973 and has been awarded to 59 individuals associated with world-class environmental accomplishments.  For more information on the Tyler Prize and its recipients, go to: http://www.usc.edu/dept/LAS/tylerprize.