March 11, 2003
What You See is Less Than What You Get... Let's take five with Moira Gunn. This is "Five Minutes".
At this point, all of us are well aware of the pollution we generate driving automobiles. Here in Silicon Valley, one of the first signs of the dot.com crash was that the freeways were suddenly less congested and you could actually see the hills across the bay. The visible effects of car exhaust were undeniable.
At the same time, I've never considered that I contribute to pollution each time I get on an airplane - but that's just changed. For one thing, jets emit substantial amounts of carbon dioxide. If you want to know your contribution, just go out to futureforests.com and specify a trip from any airport in the world to any other. In return, it will display your individual flight emissions in terms of CO2.
San Francisco to JFK? Over a 1,000 lbs. of carbon dioxide per passenger. San Francisco to Los Angeles? That would be roughly 200 lbs.
Then, I wondered: What if I drove instead of flew?
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It turns out that if I drove my car from San Francisco to LA all by myself, I would generate about the same amount of carbon dioxide as if I had flown. But if I shared the ride with someone else who originally intended to fly, we'd each save about half. Now it's awfully hard to argue that the environmentally conscious among us should take long road trips with our friends, because carbon dioxide is only one measure.
With respect to jets, we had a unique opportunity to look at the skies over the United States in the three days following 9/11. All commercial planes were grounded, and during that period, satellite images showed skies that were eerily absent of jet contrails - absent, that is, except for six particular military flights. And these flights let us see the surprisingly wide dispersion of a single contrail.
Normally there are many jets in the air, their contrails merging like high cirrus clouds. And just like a cloud, they block the sun, and simultaneously, hold in the heat. As a result, evidence now suggests that the temperature on the ground becomes a degree or so warmer during the day, and similarly cooler at night.
Somehow, I am reminded of magnificent Yosemite Valley years ago, before campfires had been banned. You'd look up, expecting to see the stars. But there were none. You couldn't see them through the smoke.
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For those of us concerned about carbon dioxide, there are a number of websites, which let us calculate our total CO2 output and make up for it by planting trees. In fact, several companies balance the business miles of their employees by a similar contribution, and Avis Europe even enables people who rent their cars to contribute to a general fund.
But the planting of trees doesn't address the jet contrails coalescing over the United States. Their ultimate effects are unknown. After all, fifty years ago, passenger jets didn't even exist.
Perhaps the gift of satellite imaging is that the existence and reach of these contrails is now undeniable to everyone who cares to look. And now that we know it, expect those familiar ethical questions to be asked many times in the years to come: What did we know? When did we know it? And what did we do about it, when we found out.
I'm Moira Gunn. This is Five Minutes.
