Changing an economic system that is bent on uncontrolled and poorly measured economic growth and depends on fossil energy for its main objectives, is much more difficult than changing how nuclear energy is used for military purposes. Some think it may be impossible.

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 need a transformation of the world economy and of how we use and share the Earth's resources. We are running out of time. We are truly at the point of no return.

The consensus is that climate change ranks along with nuclear warfare as the top two risks facing human civilization.

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

Changing the world's oceans to increase their uptake of CO2, as other geoengineering solutions propose, is equally dangerous, as the increased resulting acidity of the oceans kills tiny crustaceans, such as krill, that are the basis of the pyramid of life on the planet as we know it.

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.