TCS Daily


Cold Burn

By Russell Seitz - June 13, 2003 12:00 AM

A little climate modeling is a dangerous thing. For decades, scientists have been loading almost every gas man and nature can emit, belch, erupt or fizz forth into the atmosphere into their software-driven crystal balls, just to see what happens - at least to the output of the models.

Some amazingly subtle interactions have been discovered, that pan out in the chemistry lab as well as the computer. On occasion, these have given rise to some surprisingly large and authentically alarming results - the catalytic destruction of ozone by now-defunct spray can propellants being the pride and joy of the atmospheric chemists who got the Nobel prize for their ingenious deduction.

But pride goeth before a fall. Just as no hypothesis is so perverse that two Nobel Laureates cannot be found to endorse it, any fact of natural history may be overlooked by three or more.

Preoccupied with constant vigilance on ozone depleting gases, and greenhouse heavyweights with the lifetime of Methuselah, the Jeremiah's of the atmospheric modeling world neglected to pay much attention to the flyweight champion of the Greens, hydrogen.

What environmental harm could another part per million of water's main ingredient possibly do? The sky is so full of the stuff that it positively rains. As usual, the answer required a lot of calculation, and Cal Tech scientists only applied themselves to the requisite calculating when it became evident that the Bush administration was getting serious about the future of the hydrogen economy.

Writing in Science, they relate that if hydrogen replaced hydrocarbon fuels, and roughly a tenth of the new gas station staple got loose, enough would fly aloft to triple the water vapor content of the presently very dry stratosphere.

While down here in the troposphere, it gets cooler as you climb uphill or gain altitude, up in the stratosphere, higher is hotter, and temperature can seriously effect chemistry. Including ozone chemistry. So a green revolution in hydrogen fuels may be a recipe for a born again ozone hole, just when we thought the Montreal Treaty was cutting in enough to assure the hole's eventual demise.

But there's more, and it will not give Greenpeace joy.

Clouds happen. The higher water vapor goes, the more counterintuitive things it can do. Above the stratosphere lies the mesosphere, where higher grows colder, again. There is no law that says natural history has to be simple, and sure enough, after the mesosphere comes the thermosphere, where higher is very hot indeed. But in the high region where the stratosphere and mesosphere merge, water can turn to ice, and wispy, but spectacularly reflective noctilucent clouds can alter the Earth's albedo. The paler the planet gets, the less solar energy heat it collects, and when that energy gets reflected by the highest of clouds, it's the stratosphere that feels the cooling.

What's more, adding hydrogen can change the concentration of hydrogen dependant chemical species, like the hydroxl radical, which affect the lifetime in the atmosphere of everything from methane to carbon monoxide. So all previous modeling work will have to be repeated with corrections for the hypothetical future hydrogen that has so far been overlooked.

Jeremy Rifkin may scowl, but the spontaneous self-correction of science is a joy to behold. The serious scientific players are the ones that change their minds, and their hypotheses, whenever the data changes. But the real pleasure comes with the realization that whenever the scientific paradigm shifts, the last generation of polemics, pro and con, suffer instant and terminal obsolescence.

Will clouds at midnight chime in the specter of global cooling? Will ozone depletion disappear before a fossil fuel drought unleashes a deluge of hydrogen? Or neither? The climate modeling wars have a capacity to re-rivet our attention rivaled only by the old Republic serials. I can hardly wait for Captain Planet and the Clash of the Computers Episode 14: The Big Chill.

Pass the popcorn; this is getting interesting again.
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