Since H2O vapor is 10x more effective at trapping heat than CO2, why are fuel cell cars viewed as so green?

Question

It seems the exhaust from hydrogen and fuel cell vehicles would be much worse than from low emission gasoline vehicles for the planet. Why the hype?

A fuel cell vehcile will put much more H2O vapor into the atmosphere than a normal car would.

Answer 1

Water vapor is not an issue with regards to global warming, because its atmospheric concentration depends on the temperature of the atmosphere.

In other words, regardless of how much water vapor we emit, the concentration of water in the atmosphere will not change unless the global temperature changes.

"A [Global Warming Potential (GWP)] is not usually calculated for water vapor. Water vapor has a significant influence with regard to absorbing IR-radiation; however its concentration in the atmosphere mainly depends on air temperature. As there is no possibility to directly influence atmospheric water vapor concentration, the GWP-level for water vapor is not calculated."

Answer 2

Water vapor isn't 10x more effective than CO2 at trapping heat. It's less effective, molecule for molecule, than CO2 by a wide margin.

More importantly, water vapor doesn't stay in the air long enough for it to force climate change. Here's a thought experiment: what would happen if you could wave a magic wand and make the entire troposphere 100% relative humidity? You'd get two weeks of rain, and then everything would be back to normal. Excess water vapor in the air doesn't stay there. CO2 in the air stays there for centuries.

Answer 3

Fuel cell cars will probably be out sooner. No need to have pure hydrogen in storage. Some fuel cells can split the hydrogen off of easily obtainable hydrocarbons like methane or LPG. Since fuel cells are more than twice as efficient as internal combustion engines people will wonder how we ever got along with just having a 400 or so mile range before having to refuel.

Answer 4

yes but it's pretty easy for water vapor to preciptate out as rain, it happens constantly, whereas to remove CO2 requires a plant to convert the CO2 into plant material, and then that carbon plant material has to be put somewhere where it does not break down. A coal bed, for instance. Or a wooden table. If it just rots, the CO2 is released back into the atmosphere.

Answer 5

The hydrogen usd in the cells is harnessed from natural gas or petrol. A chemical reaction between the hydrogen and oxygen produces energy. The only by-product therefore is water. However we must realise one thing, harnessing this energy is not going to help us reduce our carbon footprint as producing the fuel itself would emitt substantial amounts of carbon dioxide combined with the extra "green" costs of fuel distribution the advantages would be cancelled out. So yes, i agree, why the damn hype? Maybe the government feels if they tell the public they are working on green fuels it might silence the public (for a short while!!) so they can get on with their unlawfull deeds instead of having to attend press conferences on green issues! OR SO THEY THINK!!!!!!

Answer 6

CO2 does not break down as easily as H2O. Water vapor is not harmful to humans but in high concentration can kill.

Answer 7

Don't quote me on this but....

i think water vapor doesnt exist in the same form for too long. Say, it becomes clouds then rain then part of a lake or ocean.
something to do with the hydrologic cycle

Answer 8

dana1981 is right: The amount of water vapor in the air is dependant upon the air temperature, not how much we emit.

Answer 9

for the very simple reason, we can inhale that water vapor and feel good, try inhaling co2 vapor and tell us the feeling

Answer 10

When the air actually cools off, it will rain water.