But motor vehicles do emit carbon.
Depending on how much oxygen is present when fuel is burned, engins emit a mixture of carbon dioxide, carbon monoxide and carbon - the latter is why you end up with a noseful of soot any time you visit London.
( The Mock TurtIe ™ --- Thinks you are a cunt, on, Thu 31 Mar 2011, 22:40, 2 replies)

Bollocks.
The soot is there because chimney sweeps are just fucking lazy these days. I blame Mary Poppins.
( Colonel Boris "...a desperate Buzzfeed imitation...", Thu 31 Mar 2011, 22:43, closed)

True
and all their apprentices are out twocking.
(Juan Quar is clinging to her front teeth on, Thu 31 Mar 2011, 22:48, closed)

The small amounts of carbon in car exhaust fall to the ground
As they're heavier than air. They are not spewed out into the atmosphere - and this is what the green lobby are talking about.

Anyway - I appreciate the pedantry :)
(EuroSong I love horse meat: best of all the animals, Thu 31 Mar 2011, 22:46, closed)

Carbon is certainly a denser material than air, but very small particles of it are light enough to be transported into the atmosphere.
They remain there because they are so light; the downward force of gravity acting on them is weaker than the force generated by the motion of the air.
( The Mock TurtIe ™ --- Thinks you are a cunt, on, Thu 31 Mar 2011, 22:54, closed)

Not always.
Many of the small soot particles become airborne (for some reason, I felt the urge to sound like Samuel L. Jackson and say "Brownian motion - do you know of it, motherfucker?"), although the effects of these particles are ambiguous in relation to climate change. In some cases, they reflect sunlight, producing a local cooling (as seen after the Indonesian forest fires) and in other cases, their colour means they may heat up in sunlight and warm the air around them.

/ more pedantry.
( Colonel Boris "...a desperate Buzzfeed imitation...", Thu 31 Mar 2011, 22:54, closed)

Lovely :)

(EuroSong I love horse meat: best of all the animals, Fri 1 Apr 2011, 14:50, closed)