Signs of a poorly understood but treatable house fire requires action, not inaction.

While denial leads to certainty, it is only the certainty of death. This is true for individuals and also for civilizations.

Political parties often take advantage of denial and fear in a moment of change. This is a well understood phenomenon that often leads to scapegoat-ism: blaming outsiders, such as immigrants, or racial and religious minorities. The phenomenon is behind Brexit and the violence in the political cycles in the US and EU.

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.

We have used the majority of our carbon budget and we are already at dangerous levels of CO2 concentrations, about 400 parts per million. The levels were 250 before industrialization. So the problem is what we have done already and, therefore, what must be undone.

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 have to remove the CO2 that the industrial economy has already emitted, which otherwise will remain in the atmosphere for hundreds of years and alter the Earth's climate irreversibly. It is possible to do this.