quarta-feira, outubro 31, 2007

No easy fix for climate

Some scientists now consider that the effects of global dimming have masked the effect of global warming to some extent and that resolving global dimming may therefore lead to increases in predictions of future temperature rise. According to Beate Liepert, "We lived in a global warming plus a global dimming world and now we are taking out global dimming. So we end up with the global warming world, which will be much worse than we thought it will be, much hotter." The magnitude of this masking effect is one of the central problems in climate change with significant implications for future climate changes and policy responses to global warming.

But it's much more complicated than an either warming or dimming issue. Global warming and global dimming are not mutually exclusive or contradictory. In a paper published March 8, 2005 in the American Geophysical Union's Geophysical Research Letters, a research team led by Anastasia Romanou of Columbia University's Department of Applied Physics and Mathematics, New York, also showed that the apparently opposing forces of global warming and global dimming can occur at the same time. Global dimming interacts with global warming by blocking sunlight that would otherwise cause evaporation and the particulates bind to water droplets. Water vapor is one of the greenhouse gases. On the other hand, global dimming is affected by evaporation and rain. Rain has the effect of clearing out polluted skies.

Climatologists are stressing that the roots of both global dimming-causing pollutants and global warming-causing greenhouse gases have to be dealt with together and soon.

Rasool, Ichtiaque, S. and Schneider, Stephen H. (July 1971). "Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate". Science 173 (3992): 138-141. doi:10.1126/science.173.3992.138