Are We Subduing Our Allies in Fight against Climate Change? New Studies Suggest That Plants and Oceans May Absorb Less Carbon Dioxide Because of Temperature Changes

Article excerpt

Lush forests and windswept oceans are two of humanity's most important natural allies in the battle against global warming. But until recently, scientists didn't know how climate change itself might weaken these allies, which absorb heat-trapping gases being pumped into the atmosphere.

Now, for the first time, scientists are getting a fuller picture of the effects warmer temperatures may have on the ability of plants and the ocean to store carbon dioxide (CO2), the "greenhouse" gas of most concern.

Researchers have found that rising temperatures have the potential to significantly reduce the amount of CO2 oceans can absorb. And although plants will continue to scrub rising amounts of CO2 from the atmosphere into the next century, they start to lose that ability as they become saturated with CO2 and face other stresses. These studies, detailed in a recent issue of the journal Nature, are "an important step forward" in the effort to better forecast the impact of human-induced climate change, says climate expert David Schimel. And while they are far from the final word on global warming, the studies could lead to better estimates on the effects of climate change - estimates that may determine how much countries reduce their reliance on coal, petroleum, and natural gas, which give off CO2 as they burn. Even small differences in the planet's CO2 budget from a climate standpoint "are enormously important economically," says Dr. Schimel, who divides his time between the National Center for Atmospheric Research in Boulder, Colo., and the Max Planck Institute in Germany. In 1995, the Intergovernmental Panel on Climate Change (IPCC) produced a set of global-warming estimates that became the basis for CO2 emission targets set last year in Kyoto, Japan. But the IPCC assumed that rising temperatures had little or no effect on the terrestrial and oceanic carbon cycles. In the latest simulation of the ocean's carbon cycle, two teams of scientists in Princeton, N.J., found that as temperatures rose, the ocean surface acted like a can of warm soda going flat - its ability to dissolve and retain atmospheric CO2 diminished. …