What does past climate change tell us?
If there’s one thing that all sides of the climate debate can agree on, it’s that climate has changed naturally in the past. Long before industrial times, the planet underwent many warming and cooling periods. This has led some to conclude that if global temperatures changed naturally in the past, long before SUVs and plasma TVs, nature must be the cause of current global warming. Ironically, this conclusion is the opposite to what peer reviewed science has found. Our climate is governed by a simple principle. When the planet has an energy imbalance, global temperature changes. Say the planet is in positive energy imbalance. More energy is coming in than going out. The planet accumulates heat and global temperature gradually rises (not monotonically, of course, internal variability will add noise to the signal). Eventually, the planet returns to equilibrium at a higher temperature. The key question is how much does temperature change for a given change in heat content. This is determin
