The more subtle thing is more speculative. The world is well past its long-term carrying capacity for human beings living a European, much less an American, lifestyle predicated on planned obsolescence. International economic growth is largely a matter of accelerated movement of materials from mines and forests to the dump. Instead of saving and buying decent furniture we can pass on to our children, we charge our credit cards for shaped heaps of sawdust and glue that fall apart in less than three or four years.

Earth Day gathered up those strands, and dozens more, and knitted them together in the public consciousness as "environmental" issues. The nation was pretty startled when 20 million people hit the streets. Congress, which had adjourned for the day to go back to its districts, was blown away.

Environmentally, business in America in 1970 was very similar to business in China today. Even if a CEO wanted to be a responsible corporate citizen, he (and they were all "he's" then) simply couldn't invest a billion dollars in pollution controls to produce a product that was indistinguishable from those of his competitors. His products would be priced out of the market. Passing laws that created a clean, level playing field for whole industries had to be a core focus of the 1970s.

An acre of windy prairie could produce between $4,000 and 10,000 worth of electricity per year - which is far more than the value of the land's crop of corn or wheat.

We need a firm cap on carbon emissions from fossil fuels. No coal, oil, or gas could enter the economy until the buyer had a permit. All permits would be auctioned by the federal government, and the number of permits auctioned would be decreased by three percent per year. Permits could be traded, but they could not be created out of whole cloth by companies that plant forests or dump iron filings at sea.

These are not exhortations from overwrought extremists, but carefully phrased warnings from some of the world's finest scientists.

We shouldn't fuel the future with the polluting methods of the past, ... We have the technology to power our future in ways that don't threaten our health or poison our planet. Let's choose to use it.