I was in my 20s when my book "The End of Nature" came out, and I was reasonably confident that our leaders would tackle the issue; when they didn’t, I tried to teach myself how to organize.

Back in those days, people my age would often tell me that "kids today" were apathetic, nothing like the activists of the 1960s or 1970s. That didn’t jibe with my experience; about fifteen years ago, when I was in my 40s, I founded 350.org, the first big global grassroots climate campaign, with seven college students. They were fantastic—and as the world has seen since, young people have emerged at the head of this fight. You know about Greta Thunberg, but rest assured: there are 10,000 Greta Thunbergs scattered around the world, and they have millions of followers.

But in the course of working with young people, I heard many of them insisting that older folks were smug, conservative, self-satisfied: endless variations on "OK Boomer." That didn’t jibe with my experience either, and once I turned 60 I decided to see if I was right. Working with wonderful friends, we’ve recently founded Third Act, an organization designed to let Boomers and the Silent Generation organize around protecting both the climate climate and the political climate: our early campaigns are about protecting voting rights, and about pressuring banks to stop lending to big oil.

In both cases, I think, older people bring particular strengths. In our first acts, we bore witness to, and perhaps participated in, the great cultural, political and social transformations of that era. We were alive for the passage of the Voting Rights Act in 1965, which may be the best thing Congress did in our lifetimes—and so it is particularly painful to watch those rights being stripped away.

Or think about the banks. Young people are leading this charge—in October they announced a first day of action outside Chase branches across America, because Chase is the biggest lender to the fossil fuel industry. (They’ve sent them almost a third of a trillion dollars since the Paris climate accords were signed). But those young people asked us older ones to accompany them—because they’re well aware that people over the age of 60 have about 70% of the financial assets in America. Bankers know whose money rests in their vaults!

Young people have particular reasons to worry about the crises that bear down on us. They’ll be in the middle of their lives right at the moment scientists tell us that climate change will be unbearable—they’re aware that the careers they’re training for now may turn out to be illusory. "We’ll all be working in disaster response," one young person said to me. But older people have their own reasons for worry. When scientists tell us that delay is fatal—that emissions must be cut in half by 2030 if we’re to have a chance of reaching the targets the world set at Paris—we get that. We have a psychological sense of deadlines that the young still, blessedly, lack. That’s why our slogan at Third Act is No Time to Waste.

It’s been great fun getting this work off the ground—everyone from Norman Lear, in his hundredth year, to Jane Fonda, in her 83rd, to Greta in her 18th, have pitched in to help. But mostly it’s just regular people, those of us who are uneasy about the world we’re leaving behind, and convinced that we have acquired in our lifetimes the skills and resources to do something about it. There’s only one way to find out!

Bill McKibben has written 20 books, gotten 20 honorary degrees, and been arrested 11 times. You can follow his work at billmckibben.substack.com