The Earth System and its Ever-Changing Nature

4.6 billion years of global change

Abrupt climate change

The Human Factor

A short history of human impacts

The future: why some people are so concerned while others aren't

Good Intentions and Geoengineering

Good intentions gone awry

Geoengineering schemes

The record on smaller-scale attempted modifications

Further Cautionary Considerations

The possible fallibility of even a strong consensus

The unknown future: model limitations

Compounding social pressures

Avoiding Paralysis Despite Uncertainty

What are the alternatives?

Closing plea.