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Name: Jacob
Status: Other
Age: 15
Location: CA 
Country: United States
Date: November 2, 2005


Question:
My question is about hydrogen technology. Now I assume the promoted use of hydrogen fuel cell technology in cars is the reduction in greenhouse gas. But, water vapor itself is a greenhouse, gas, and I am not sure as to the relative production of CO2 vs water vapor between traditional cars and fuel cell technology, but as a greenhouse gas does water vapor absorb more or less of the sun's radiant energy than CO2?



Replies:
Water is probably the most "active" greenhouse gas. It has 3 intense vibrational absorptions and a rich rotational spectrum in the infrared region of the electromagnetic spectrum. In contrast, CO2 has 2 infrared active vibrational absorptions and no rotational absorptions (since it is a non-polar linear molecule). In addition, or on the other hand, depending upon how you want to look at it, water is involved in many feedback systems, both positive and negative: cloud/rain/ice/snow formation, absorption by plants and animals to mention only a few. So it is very difficult to model the water cycle and how it plays out in the energy exchange. In addition it is by far the most abundant of the greenhouse gases. Some of the early atmospheric models appear to have ignored the role of water at all. I am not an expert in this area but I certainly think that any climate model that does not take the role of water (in all its forms) into account is highly suspect regarding predictions about climate change. At the risk of appearing anti-environmental, which I am not, I think it is appropriate to question the assumptions of any given model.

In the 1960's it was "population explosion" that was supposed to bring about catastrophe before the turn of the century. It didn't happen. From a scientifically critical perspective it is important to ask the "unpopular" questions and to challenge the "conventional wisdom". Scientific answers are seldom answered on the OP-ED pages of the daily newspaper. Given that global climate data is barely 50 years old (at best) it is too easy to jump to conclusions based on a very short baseline. That may be unpopular but science must ask the unpopular questions.

Vince Calder


Jakub,

The relative importance of greenhouse gases in absorbing energy is:

water vapor 50-60%
carbon dioxide 15-20%
ozone 5%

Considering that, adding water vapor to the air from vehicles might be a concern. Most scientists would probably say that the amount emitted from vehicles presently and from hydrogen fueled vehicles in the future would be so small compared to what is already in the atmosphere that it really wouldn't be a big concern for enhanced greenhouse warming.

One thing is for sure, the reduction in emissions of carbon dioxide from hydrogen fueled vehicles and power plants would be very beneficial in preventing, or at least slowing, possible global warming.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory



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