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Wattage
Tue Apr 27, 2004
Listen in RealAudio 
One of the biggest questions about Global Warming is: how close are we to the brink
of dire consequences, and can we possibly recover? A new article by James Hansen,
director of NASA's Goddard Institute for Space Studies ponders those issues. Hi, I'm
Bryan Yeaton, and this is The Weather Notebook's weekly show about climate
change.
Hansen's article, published in the March edition of Scientific American, looks at global
warming from an energy perspective. He equates the effect of human-driven warming
to a Christmas tree bulb that dissipates about one watt of heat. Although that doesn't
sound like much, when you place two bulbs in every square meter of planetary surface,
including the oceans, it adds up to a global two-watt per square meter increase. Since
the late 1800s, Hansen says that has translated to a 1 1/3 degree F jump.
Hansen pins the blame of these increases on a variety of factors: greenhouse gasses
like carbon dioxide and methane, but also on aerosols like sulfates and black carbon,
or soot. We have a fairly good handle on how the gasses are working in the
atmosphere, but the effect of the aerosols is more complex, and less understood.
Some aerosols actually reflect energy back into space while others change the
properties of clouds.
Right now, according to Hansen, the planet is adjusting to a new energy balance, but
he doesn't believe we will necessarily experience significant consequences -- if we act
now and hold warming to within one watt per meter over the next half century. In fact,
the reduction of methane could help offset atmospheric CO2, even levels remain
static.
The result of this action, according to Hansen, would be to not only slow or stop global
warming, but also to improve the quality of the air we breathe.
The Weather Notebook receives support from the National Science Foundation and
Subaru of America.
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