Looking for a book about people chosen to go into hibernation because Earth is too polluted

Question

I read this book in the 70's when I was 11 years old and now I'm trying to find it again.

As I remember it, the plot is somewhat like this:

Earth is really polluted and everyone will die. But this organization is secretly selecting people to go into hibernation for a few thousand years until Earth regenerates. Then they will wake up and repopulate the Earth. The selected people get phone calls with riddles and clues that they have to solve (but they don't remember them) until they solve the riddles and find the place where they must go to be a part of this.

This is the book that first made me aware of environmental issues and I would just love to read it again.

Answer 1

This sounds like the resolution to the mystery that they are trying to solve in The Missing Persons League, by Frank Bonham, which was first published in 1976.

The same book is described in this answer, too.

As you can see from the synopsis from goodreads below, the plot is that Earth is polluted and the main character knows that it won't be able to support life within 2 years. The book revolves around his trying to find out what happened to missing people, and discovering the secret organization you describe.

Brian's sister and mother vanished without a trace over a year ago. It was not uncommon. People were disappearing everywhere. To Brian, life had become a frightening madness. He knows that in another two years the planet will be unable to support life. Now suddenly, his father is gone. Fighting the panic that haunts everyone, Brian resolves to find his family before it is too late. Joined by his beautiful friend Heather, he begins a dangerous search through abandoned shipyards, a burned out park, and finally a deserted jewelry arcade. And they are not alone. Clearly, the government will stop at nothing to find these people who seem to have vanished into the earth's rancid air. And though Brian doesn't understand why, he knows that it is a deadly contest he cannot afford to lose.