We know little of the consequences of the geoengineering process, such as spraying particles into the atmosphere that shade the planet from the sun's rays and could decrease its temperature. But this process is how dinosaurs disappeared from the Earth about 60 million years ago, by particles spewed by a volcano or a giant meteorite impact, and our species could follow suit.

We are in the midst of the 6th largest extinction event in the history of the plant and the first caused by human action.

Even if we planted a tree on every square yard available in the planet by the end of the century we would only capture at most 10 percent of the CO2 we need to reduce. This does not mean that we should not plant trees; we should, for biodiversity's sake, and for our long-term future together with the other species.

The new markets that arise from ecological constraints will dominate the 21st century economy, and so will markets for knowledge.

If nuclear warfare is believed to be somewhat controlled, then climate change is now the greatest threat.

As difficult as it is to eliminate the risk of nuclear warfare, it requires fewer changes to the global economy than does averting or reversing climate change.

Trying to conserve a privileged global position makes change traumatic for the US.