500 million years of climate history pinned on plate tectonics
Enlarge / Indonesia's Paluweh volcano sits in a region of colliding tectonic plates—perhaps the formula for glacial periods in geologic history. (credit: Robert Simmon/NASA Earth Observatory)
Generally speaking, it’s easy enough to make sense of the last few million years of climate patterns—the world looked much as it does today, so changes in greenhouse gas concentrations or ocean circulation can be related to what we see now. But as you go back farther in time, you can find very different climates and a rearranged map of continents, and those require more creative thinking.
For example, the ice age periods in the recent past are not unique. But most of the last 500 million years have been much warmer—what has caused the climate to slowly drift toward warmer or cooler temperatures over millions of years?
Looping
In the grand sweep of Earth history, its climate has remained within a habitable temperature range—thanks in part to the moderating influence of feedback loops within the system. The weathering of silicate minerals in bedrock pulls CO2 out of the atmosphere, for example. In a warming climate, weathering can speed up, removing more greenhouse gas and stabilizing temperatures. Cool the planet and weathering slows, giving greenhouse gases more chance to accumulate.