Most people probably haven't yet heard of the related concept, "global dimming," which is the reduction of direct irradiance from the sun at the Earth's surface due to particulates from pollution in our atmosphere and clouds that block and reflect sunlight. Global warming is a heating process; global dimming is a cooling process.

Scientists believe that pollution-caused GD has masked the true extent of global warming. Therefore, as we reduce man-made air pollution, the resulting decrease in GD may actually increase the rate of future temperature rise from global warming. With this in mind, reducing our heavy reliance on fossil fuels for energy and transportation should be a high priority. Oil shale is not the answer. As a fossil fuel, it is part of the overall problem.

PBS's NOVA has an excellent program called "Dimming the Sun," which recently aired (go to www.pbs.org/wgbh/nova/sun/ for more information).

Shane Larsen

Bountiful