"Man-made climate change may have began in the last two hundred years, but humankind has witnessed many eras of climate instability. The results have not always been pretty: once-mighty civilizations felled by pestilence and glacial melt and drought. But we have one powerful advantage as we face our current crisis: history. The study of ancient climates has advanced tremendously in the past ten years, to the point where we can now reconstruct seasonal...