Friday, May 14, 2004
Global Darkness
As if the planet did not have enough problems, Kenneth Chang now reports that the world has literally become a darker place. Turns out the amount of sunshine earth has receives has dipped from between 10% to 37% depending on where you live.
No one is predicting that it may soon be night all day, and some scientists theorize that the skies have brightened in the last decade as the suspected cause of global dimming, air pollution, clears up in many parts of the world.Yet the dimming trend — noticed by a handful of scientists 20 years ago but dismissed then as unbelievable — is attracting wide attention.
Satellite measurements show that the sun remains as bright as ever, but that less and less sunlight has been making it through the atmosphere to the ground. Pollution dims sunlight in two ways, scientists theorize. Some light bounces off soot particles in the air and goes back into outer space. The pollution also causes more water droplets to condense out of air, leading to thicker, darker clouds, which also block more light. For that reason, the dimming appears to be more pronounced on cloudy days than sunny ones. Some less polluted regions have had little or no dimming. The dynamics of global dimming are not completely understood. Antarctica, which would be expected to have clean air, has also dimmed.
No one is predicting that it may soon be night all day, and some scientists theorize that the skies have brightened in the last decade as the suspected cause of global dimming, air pollution, clears up in many parts of the world.Yet the dimming trend — noticed by a handful of scientists 20 years ago but dismissed then as unbelievable — is attracting wide attention.
Satellite measurements show that the sun remains as bright as ever, but that less and less sunlight has been making it through the atmosphere to the ground. Pollution dims sunlight in two ways, scientists theorize. Some light bounces off soot particles in the air and goes back into outer space. The pollution also causes more water droplets to condense out of air, leading to thicker, darker clouds, which also block more light. For that reason, the dimming appears to be more pronounced on cloudy days than sunny ones. Some less polluted regions have had little or no dimming. The dynamics of global dimming are not completely understood. Antarctica, which would be expected to have clean air, has also dimmed.
