Saturday, October 23, 2021

A Very Interesting Graph

Someone on Facebook commenting on my post there linked to an NOAA web page with a graph showing temperature, CO2, and insolation for the past 350,000 years. The pattern is interesting. During the previous three interglacials (yellow columns on the graph) temperature was falling. During two of the three, CO2 concentration was also falling, during the third roughly constant.

Compare that to the latest interglacial, the one we are living in. It starts on the figure about 11,000 years ago. Temperature and CO2 initially fall but after two or three thousand years the pattern reverses and they start rising.

Could we be responsible?

That is about eight thousand years too soon for the industrial revolution but only a little after the beginning of the Neolithic revolution, the rise of agriculture and just about right for the spread of agriculture to Southwest Asia. Is it possible that the change in human activity, the enormous growth in human population with the switch from hunter-gatherer to farmer and associated activities such as forest clearing, somehow caused an increase in CO2 and temperature during the interglacial? Is it possible that that increase is the reason the current interglacial, which has already lasted longer than its three predecessors, has not yet ended?

Perhaps we owe thanks to our stone age ancestors for the glaciers not yet having started south.