But we don&#x27;t know that the endgame is extinction of the race. We don&#x27;t even know when various benchmarks will occur ( say, sea level at x% higher ) .<p>The physics of a Venus aren&#x27;t on the table - SFAIK, all the carbon we&#x27;re digging up and burning was once animal or vegetable matter, derived from a Carboniferous era level of atmospheric CO2.