"Eliminating all U.S. gasoline powered vehicles would reduce worldwide carbon dioxide emissions by 0.18%."
Is this statement true?
It could be. Automobile emissions make up about 20% of man made emissions (IIRC), the US produces 22% of world emissions; so that's roughly 4.5% of all man made emissions.
Man made emissions contribute roughly 5% of all emissions so that gives a figure of about 0.2% of all CO2 emissions coming from US gasoline powered vehicles which about lines up with your figure, and mine is very back-of-an-envelope.
If so, then surely at least as regards cars and the like (which we're getting taxed on now to stop using) it's a lot of fuss about nothing isn't it?
No, this doesn't follow at all. Looking at it as a % of total CO2 emissions is utterly misleading. The 150 billion tonnes or so of carbon kicked out by natural environment was in equilibrium with the 150 billion tonnes or so absorbed by the natural environment; the 7 billion or so tonnes a year extra we're adding are not in equilibrium (roughly 3 billion tonnes of it get absorbed by increased plant growth; leaving about 4 billion extra in the atmosphere each year).
The upshot of this is that in 1850, atmospheric carbon dioxide was about 280 parts per million, and today it is about 385ppm. So that little 5% extra we're emitting each year has increased atmospheric carbon dioxide by over a third; and it will keep on going up.
That matters because CO2 absorbs infrared radiation, and so traps solar energy that would otherwise be radiated out to space. It's not a big effect, but it doesn't need to be; our atmosphere results in our planet being about 50 degrees hotter than it would be without it. If increases in CO2 raise the amount of energy absorbed by just 4% that's a 2 degree rise in average global temperatures - which may not sound a lot but it will have drastic effects in terms of agriculture in large parts of the world and sea level rises, as well as the spread of diseases and the already fragile ecosystems that we rely on. CO2 alone won't produce this rise; in fact water vapour contributes more to the greenhouse effect than CO2 but a side effect of temperature increases from CO2 levels will be a raise in water vapour compounding the temperature increase.
Going back to the cars for a moment; dealing with cars, even eliminating them, won't solve the problem. We should be looking much more at domestic, and commercial, emissions. I rather suspect we're not because it's politically a lot more tricky to tackle than just battering on us car users.
Finally, one other thing your figure illustrates is that no one country, even a giant like the US, can tackle the problem alone.
(Note: the figures I've given are mostly off the top of my head and roughly ball park figures; I don't vouch for their precision but they're close enough to be meaningful)
