Pollen production -- and allergies -- may rise significantly over next 50 years

Ragweed, which flourishes along roadsides and in disturbed habitats throughout North America, produces one of the most common allergens. A study by Harvard researchers found that ragweed grown in an atmosphere with double the current carbon dioxide levels produced 61 percent more pollen than normal. Such a doubling of atmospheric carbon dioxide is expected to occur between 2050 and 2100. "The side effects of carbon dioxide, as well as its impact on heat budget and the water cycle, have to be taken very seriously," said Paul Epstein, Harvard Medical School instructor in medicine and associate director of the Center for Health and the Global Environment at HMS.

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