9 October 2003
Major Climate Changes Predicted For US
by Kate Melville

Over the next 100 years, the eastern United States will see more winter precipitation because atmospheric carbon dioxide levels are increasing. But more precipitation does not necessarily mean more snow, according to Arthur T. DeGaetano, a Cornell climatologist who was one of several speakers at the Impacts of Climate Change on Horticulture symposium, held last week.

The symposium focussed on implications of climate change and increasing atmospheric carbon dioxide for the important fruit, vegetable and ornamental horticulture industries, said David Wolfe, Cornell professor of horticulture and one of the symposium's organizers. The meeting brought together climate scientists, horticultural researchers, extension educators, horticultural businesses, environmental and gardening groups, and representatives from public gardens.

The program featured speakers on climate change, plant and plant-pest responses to greenhouse gases and climate, and development of educational and "citizen-science" programs. Among the speakers: Mark Schwartz of the University of Wisconsin-Milwaukee discussed changes in the North American spring as indicated by lilac blooms; Mary Peet of North Carolina State University examined yield and quality responses of horticultural crops to carbon dioxide and temperature; Richard Bisgrove of the University of Reading, England, talked about climate change impacts on public and private gardens and landscapes; and John Reilly of the Massachusetts Institute of Technology examined the recent national assessment of climate change impacts on agriculture.

Prompting the symposium is the noticeable shift in first-leaf and first-bloom dates of plants over the past several decades in the United States and Western Europe, says Wolfe.

Most horticultural plants are highly sensitive to climate change, as atmospheric carbon dioxide concentrations, temperatures and precipitation amounts rise. "Climate change and carbon dioxide are likely to alter important interactions between horticultural plants and pollinators, insect and disease pests and weeds," Wolfe says.

Few scientists disagree on global warming. The question is how will global warming affect regions. "While virtually all models predict that global - and in many instances, regional - temperatures will rise through the next century as carbon dioxide levels approach twice the pre-industrial era level, there is disagreement on changes in precipitation amount," says DeGaetano, Cornell associate professor of climatology and the director of the Northeast Regional Climate Center at Cornell. "In a situation where the globe is going to warm, there are physical reasons for precipitation to increase, particularly during the winter," he says.

In his presentation, DeGaetano explained how the western United States likely will see more winter precipitation but, overall, less snow, while the Midwest and Great Plains may see an exaggeration of the water cycle. And this means, he says, more extreme climate events, like drought and flooding.