Asbestos, EMFs, and CFCs have given us a degree of humility. When yesterday's "triumph of modern chemistry" turns out instead to be today's deadly threat to the global environment, it is legitimate to ask what else we don't know.

With time environmental issues got much more complicated. It is pretty easy, if you know what you are doing, to stop a company from pouring poison into a lake where kids swim. It is much harder to address all the myriad greenhouse gases emitted by different sources - from petrochemical refineries to hundreds of millions of peasants cutting down trees for their incredibly inefficient cook stoves.

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.

By 1975 - and continuing to today - all Americans came to believe that they had a "right" to a safe, clean, healthy environment. When I grew up, no one seriously criticized the steel mills and paper mills for the deadly stench they produced - that was the smell of prosperity. In the modern society, no one would tolerate such conditions in an American city.

We presently have the technology ... fuel cells, solar cells, hydrogen ... the opportunities are amazing for clean energy.

There really wasn't an environmental movement 30 years ago. The Sierra Club national office in 1969 consisted of one full-time volunteer.

We've made some heroic efforts, but the Earth as a whole is in worse shape today than 30 years ago, ... There's been 30 more years of greenhouses gases, species extinctions and population growth.