I've been accused of oversimplifying the situation:

We are not creating more carbon, we are merely redistributing it back into the atmosphere (from whence it originally was located and fixed by the plants which then died and became oil).

If we heat up and drown (or burn up), some other species will take over. What is the big problem with that?

Evolutionary theorists say this happens regularly on this planet. Are you saying the human race should not be held to the same hypothesized guidelines of the Evolutionary model as other species?

I guess Creationists could argue that the human race should not be subject to the "temporarily dominant species" rules, but if this model were accurate, the 'free will of man' provision would be the reason we smote ourselves.

Simlarly, supporters of the intelligent design theory might justify the same outcome as a result of our decisions

Chaos theorists who support the notion that we're just a freak mathematical probability could side with the evolutionists

I don't know what other theories for "why are we here" are out there, but would be interested to hear a synopsis of them.

And we're supposed to have several hundred "Bill-yon" (props to Carl Sagan) years before the "Big Rip" where all atomic matter eventually dissociates into nothing (apparantly in conflict with the first law of thermodynamics, but I'm just a silly insurance salesman), so sail now before it all goes to hell!