We need to invest at a scale that has never — ever — been seen in human history. How much am I talking? My estimate is about $20 trillion. Per year. That’s the size of the American economy, by the way. It is a tremendous number. That is how much it will cost to really begin creating a future and a planet that is fit for life again, instead of spiralling into fire, flood, plague, and chaos. That is what it will take to create a world of clean energy grids, green construction, breathable air, drinkable water, and so on.