I've been reading up on hydrogen powered cars. The people who write about hydrogen powered vehicles talk a lot about eliminating "greenhouse gas" in the exhaust. These people are, of course, convinced that CO2 is causing global warming that threatens the world. They seem unaware that water vapor is a more significant greenhouse gas than CO2. It is not clear to me that a world-wide fleet of hydrogen fueled vehicles would be less disruptive to the atmosphere than the current gasoline fueled vehicles. It seems to me that someone needs do some analysis on what the effect of so much water vapor would be. Maybe it would not be a problem, but that is not obvious. Some of the people writing about hydrogen powered vehicles seem unaware that hydrogen is a "carrier" rather than a fuel. Energy has to be applied somewhere to convert water to hydrogen and oxygen. The hydrogen also has to be compressed or liquefied in order to be conveniently used to power an auto.

It appears to me, without doing any analysis, that use of nuclear power to generate electricity to charge battery powered vehicles would be the best approach for reducing emissions into the atmosphere. There is a need for better batteries if internal combustion vehicles, or fuel cell powered vehicles, are to be made obsolete. THe current state of the art for batteries limits electric cars to short range so that they are only practical for traveling around town, commuting to work, etc. The near-term (next 20 or 30 years) outlook may be for two-car families to have one electric car for commuting and one conventional IC engine car for longer trips. Or, maybe people will just rent a car for out-of-town trips. The timing on this will depend on whether or not the next few years show that CO2 emissions are actually causing the earth to heat excessively. At present that appears to not be happening, but politicians are acting like it is, and once they get started on a path are not much influenced by reality, so may use some incentives to promote the use of electric cars while discouraging development of petroleum sources. There is potentially enough petroleum to fuel cars for centuries, particularly if we would use nuclear power to generate electricity. Lobbyists and special interests influence these things in ways that we in the public are not warae of, and cause politicians to implement policies that are not necessarily the most logical or best.