[Gert]

Gert asked the Naked Scientists:
   
Water vapour is a greenhouse gas. This said, would a hydrogen-driven car contribute more, less or the same to the greenhouse effect as a gasoline driven car?

I'm not just thinking of the contribution while driving the car, but also the production of the fuel.

What do you think?

[Geezer]

I doubt that the amount of water vapour released by the car would have any significant effect on the climate.

It's really a question of net increase in CO2 by the consumption of fossil fuels, so it very much depends on how the hydrogen was produced. If it was made entirely from non-fossil fuel energy sources, which is possible, there would be no increase in CO2.

The advantage of the hydrogen powered vehicle is that it at least makes it possible to eliminate a net increase in CO2, and even if there is some CO2 created in the production of the hydrogen, it may be less than the amount that would have been produced if a fossil fuel had been burned in the vehicle.

[norcalclimber]

But water vapor is believed to increase the warming potential of CO2.  If so... isn't it possible that if 100 years from now we have completely converted to hydrogen cars that we might get warming similar to CO2 warming?

[Geezer]

But water vapor is believed to increase the warming potential of CO2.  If so... isn't it possible that if 100 years from now we have completely converted to hydrogen cars that we might get warming similar to CO2 warming?

I don't think there is any net increase in water vapour in the atmosphere as long as the hydrogen was derived from water in the first place. There might be some localized increases in water vapour, but that is a very different situation from increasing net CO2 in the atmosphere by oxidising fossil carbon.

BTW, I don't think there is anything intrinsically wrong (from a climatic perspective) with burning carbon based fuels in vehicles that produce carbon dioxide as long as the carbon does not come from a fossil source.

A contrarian might even suggest that California didn't really do anyone a favour by leading the way on emission standards. To some extent, the improvement in emissions has helped to conceal the real problem - fossil carbon.

[norcalclimber]

But water vapor is believed to increase the warming potential of CO2.  If so... isn't it possible that if 100 years from now we have completely converted to hydrogen cars that we might get warming similar to CO2 warming?

I don't think there is any net increase in water vapour in the atmosphere as long as the hydrogen was derived from water in the first place. There might be some localized increases in water vapour, but that is a very different situation from increasing net CO2 in the atmosphere by oxidising fossil carbon.

BTW, I don't think there is anything intrinsically wrong (from a climatic perspective) with burning carbon based fuels in vehicles that produce carbon dioxide as long as the carbon does not come from a fossil source.

A contrarian might even suggest that California didn't really do anyone a favour by leading the way on emission standards. To some extent, the improvement in emissions has helped to conceal the real problem - fossil carbon.

Very interesting point.