Carbon dioxide in the atmosphere warms Earth. But just how much warming you get depends on where you put your continents.
If adding carbon dioxide to the atmosphere creates a greenhouse effect that warms Earth, it must have happened in the past. That’s why paleoclimatology, once a small and esoteric field, is such a growth industry these days, with legions of geologists trying to glean past temperatures and CO2 levels from rocks, and legions of climate modelers trying to tell us what it all means--not only for the past but also for the future of Earth’s climate. On the whole, the results have been what you’d expect. When carbon dioxide levels were low, the climate was cold, and when they were high, the climate was warm, says climatologist Thomas Crowley of Texas A&M; University.
But lately two glaring exceptions to that simple rule have turned up. During the Ordovician Period, ...
