James Hansen is not the only eminent scientist expressing the view that burning all the world’s fossil fuels could produce a huge amount of warming. Richard Alley, whose book on ice cores I reviewed earlier, responded to such a question at the end of this excellent and informative talk of the climatic history of the Earth and how we know it.

Alley expresses the view that burning all the world’s fossil fuels, including oil shales, could return the Earth’s climate to where it was during the Cretaceous, when average temperatures were over 20ËšC higher than now.

It doesn’t take much imagination to see how much disruption such a colossal rise in temperatures would generate. All of our infrastructure and agriculture would find itself poorly matched to the new conditions in which it existed.

The talk also does a very good job of explaining why we are so confident about aspects of the paleoclimate record – in particular, the importance of CO2 concentrations in determining the state of the climate system.