The fossile deposits (gas,oil,coal) will be used up anyhow.
There will always be a country who treats them as valuable goods.

So their carbon deposits will be emitted into the athmosphere
either way. (no matter if in 50 or 200 years)

Using low energy car and such will simply delay that
emission over time. With the same end-result.

Some small recent games of mine:
Griefer 4k http://damocles11.byethost9.com/griefer4k.html
Kobold 4k http://damocles11.byethost9.com/kobold.html
Cave 4k http://damocles11.byethost9.com/cave4k.html