"does not become a fuel until it is burning"

Well by that standard, neither would petroleoum... :-)

... and by that standard, Logic.... :-P


"changes in atmospheric CO2 lagging or preceding temperature changes, because it varies with latitude."

Complicating this overly simplistic approach is the fact that there is constant circulation between the various lattitudes...

As to the source of crude oil, it has been established that many large lumps of 'organic matter' whizz around in space. When the Earth coalesced, such lumps would have been ' buried' all over the place... However, I remember clearly being told as a child that oil & coal came from old forests.... so that MUST be true.... :-P