Carbon Cycle Feedbacks
The carbon cycle as presented in Chapters 8 and 9 generally has a calming influence on climate. The ocean takes up most of the fossil fuel CO2 in a few centuries, leaving some behind, in a fairly well-behaved, predictable way. Our only complaint was that the carbon cycle was so slow to clean up the mess.
The carbon cycle from the real world, as documented in ice cores and other climate records, seems to have had a different temperament. Instead of moderating the climate changes that were driven by orbital variations, the carbon cycle seems to fan the flames of climate change. It is likely that, given time, the carbon cycle will amplify the effects of global warming in the future, as well.
There are times in the past in which warming seemed to trigger atmospheric CO2 to rise. The interplay between temperature and CO2 is tricky to untangle because an increase in CO2 drives the Earth to warm, but here I claim that a natural change in temperature may also drive CO2 to change. Put the pieces together into a loop of cause and effect, and the result is a positive feedback that makes the climate tippier.
One example is the warming and rising CO2 concentration at the end of the glacial time, already presented in Chapter 5 and