Cahokia's lessons on failure, climate change

Your article on Cahokia was important for two reasons.

First, anybody who has been to Cahokia knows that it is a fascinating place. Cahokia was bigger than Paris and London 1,000 years ago. The fact that Cahokia went from such a success to a total failure should also be a lesson for everybody.

The second reason is the importance of climate change. As your article mentions at least twice and the visitor's center at Cahokia points out, climate change 1,000 years ago probably led to a decrease in crop outputs which eventually led to the abandonment of Cahokia. That happened during the "Medieval Warming Period" when temperatures also rose in Europe but tripled crop outputs there, which increased the population and led to the spectacular Renaissance.

To a rational person, this raises a critical question; how many coal-fired electric plants or SUVs were at Cahokia 1,000 years ago? Zero. Anybody who has actually studied history and the climate knows that climate change is a never-ending natural process that has been going on for 4.5 billion years, which brought at least six great ice ages and then melted them.

There are four major causes of natural climate change; 1) Changes in the sun's solar output, 2) Changes in the tilt of the Earth's axis, 3) Continental drift, which changes ocean currents that impact weather and climate, and 4) Changing wind currents.

You will notice that CO2 didn't make the list. That's because CO2 today only makes up 0.04 percent of our atmosphere, which is at a low point in Earth's history, not a high point. Yes Cahokia is a fascinating place and there is a lot to learn from it even today.

Randy Rossi

Grayslake