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

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

The "can do" logic, by its own nature, does not accept limits. And an empire does not have a graceful way to evolve out of this role. History demonstrates this time and again.

We know that the warming rising seas will swallow entire island nations that are about 25 percent of the UN vote and perhaps at the end, even our civilization. This realization is traumatic and the first reaction to trauma is denial. Since there is some remaining scientific uncertainty, a natural response is to deny that change is occurring. This is natural but it is very dangerous.

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

CO2 from air can replace petroleum: it can produce plastics and acetate, it can produce carbon fibers that replace metals and clean hydrocarbons, such as synthetic gasoline. We can use CO2 to desalinate water, enhance the production of vegetables and fruit in greenhouses, carbonate our beverages and produce biofertilizers that enhance the productivity of the soil without poisoning it. Carbon negative technology is absolutely needed now.