Eh, you can worry about global cooling as a hypothetical outcome -- for instance, there is a "snowball Earth" feedback loop with the albedo of ice sheets -- but

Eh, you can worry about global cooling as a hypothetical outcome -- for instance, there is a "snowball Earth" feedback loop with the albedo of ice sheets -- but from a geoengineering perspective releasing CO2 into the atmosphere isn't that hard, and we've still got more than half of the known oil in the world left.