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Water as a Greenhouse Gas Earth
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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