Ozone, nitrogen change the way rising CO2 affects earth's water

NASA/Jet Propulsion Laboratory: Through a recent modeling experiment, a team of NASA-funded researchers have found that future concentrations of carbon dioxide and ozone in the atmosphere and of nitrogen in the soil are likely to have an important but overlooked effect on the cycling of water from sky to land to waterways.

The researchers concluded that models of climate change may be underestimating how much water is likely to run off the land and back into the sea as atmospheric chemistry changes. Runoff may be as much as 17 percent higher in forests of the eastern United States when models account for changes in soil nitrogen levels and atmospheric ozone exposure.

"Failure to consider the effects of nitrogen limitation and ozone on photosynthesis can lead us to underestimate regional runoff," said Benjamin Felzer, an ecosystem modeler at Lehigh University in Bethlehem, Pa. "More runoff could mean more contamination and flooding of our waterways. It could also mean fewer droughts than predicted for some areas and more water available for human consumption and farming. Either way, water resource managers need more accurate runoff estimates to plan better for the changes."

…The amount of water that plants give up depends on how much carbon dioxide is present in the atmosphere. Studies have shown that despite a global drop in rainfall over land in the past 50 years, runoff has actually increased….

View of runoff, also called nonpoint source pollution, from a farm field in Iowa during a rain storm. Shot by Lynn Betts, U.S. Department of Agriculture, Natural Resources Conservation Service