He specifically identifies oil shales as a big reserve, and says that if we burn all of it there is “some chance of getting above [the] Cretaceous level.” At that stage in Earth’s history, mean global temperatures were 37˚C to 38˚C.

According to NASA, the “[b]est estimate for absolute global mean for 1951-1980 is 14.0˚C” – about 23˚C cooler than the Cretaceous.

As Alley says: “You can think of a ‘burn it all’ future getting really hot.”

He uses the analogy of credit card debt. Interest lags debt. You overspend and go into debt, interest accumulates on the debt and the debt grows. You cannot predict the quantity of debt at any particular time without taking interest into consideration.

Similarly, some orbital changes cause warming, which causes CO2 to rise, which causes more warming. You cannot explain what happened to the climate system without taking that reaction into account.

[Processes involving continental drift] take 50 million years or 100 million years. And so you’re going to see big changes in CO2 over long times as you tweak these things.

Evolution: when you get land plants it changes – you can now make coal. If you don’t have land plants, you can’t make coal. If you can make coal, you can bury organic carbon. So evolution is going to affect carbon over long times and mountain building and plate tectonics… are going to affect CO2.”

“We are beginning to tease apart the sequence of abrupt climate change,” said White, whose work was funded by the National Science Foundation’s Office of Polar Programs. “Since such rapid climate change would challenge even the most modern societies to successfully adapt, knowing how these massive events start and evolve is one of the most pressing climate questions we need to answer.”

Filed under:
* Paleoclimate
* Climate Science

Many people hold the mistaken belief that reconstructions of past climate are the sole evidence for current and future climate change. They are not. However, they are very interesting and useful for all sorts of reasons: for modellers to test out theories of climate change, for geographers, archaeologists and historians to examine the impact of climate on past civilizations and ecosystems, and for everyone to get a sense of what climate is capable of doing, how fast it does it and why.