I always get suspicious when people say they doubt global warming. I tend to assume they have a vested interested in 'releasing carbon that was removed long ago'. I'll give you the benefit of the doubt, though :)

Actually, the global carbon cycle has very little to do with fish, dinosaurs, or, indeed, Steve Irwin. The main thing is the algae, specifically the coccoliths that produce calcium carbonate skeletons that don't get recycled when the die. These form chalk deposits on the ocean floors.

The balance to this is the subduction of the ocean floors which results in the release of CO2 through volcanoes.

This is one of those little-known, but absolutely stunning equilibrium things. If the volcanoes stopped emitting, all the available CO2 would end up at the bottom of the ocean in a couple of million years. Equally, there's more than enough carbon sequestered down there to turn this planet into Venus if it were released more quickly than the coccoliths deposit it. Yet, over the last several hundred million years the two process have always balanced closely enough to keep the Earth hospitable.

But of course, this gets us away from the crux of the matter. Arguing that the Earth was warmer in the Carboniferous, or even the Pliocene, may be looking at the 'big picture', but it's perhaps looking at a slightly too big a picture.

The current biosphere is adapted to the current conditions (or perhaps slightly colder). Human technology, culture, and geographical distribution is similarly adapted.

The real 'big picture' is that atmospheric CO2 concentrations have doubled since the start of the Industrial Revolution - and most of that in the last 40 years. For some reason, people who hop up and down about things like genetic engineering of crops and nuclear energy don't seem to be as scared over a global change that will have genuinely uncertain consequences. There are parallels with ozone depletion issues - perhaps smokestacks and aerosols just aren't things people can be afraid of. In both cases getting an international treaty was a long and difficult process and in both cases major powers refuse to play their part in solving the problem.

Eventually our reliance on fossil fuels will have to end, if only because there's only a finite quantity available. If the transisition to alternatives can be expedited at a reasonable cost (and the costs do seem quite reasonable) as a precaution against the consequences of rising CO2 levels, that seems like a prudent thing to do.

Thank you for this comment! I've always, always wondered about the affect of life on the carbon cycle, and nobody'd ever really addressed it.

I didn't mean to imply I doubt global warming. It's growing increasingly obvious that it is happening. But I think it's also pretty obvious that it may be impossible to do anything about it.

I guess my main argument should've been that the climate will change (is changing?), people on the coasts will eventually have to move inland, but it most definitely won't be the end of the world.

Again, thanks for the post!