Each of us can and must shift our behavior according to our ability. For some, that means changing diet, shopping locally, or putting solar panels on their house. For others, it means using their voice to inspire transformative change.

I was raised a Catholic as a boy and went to a Catholic boys' high school, a private school, and kind of drifted away, candidly, in my latter teen years. I consider myself deeply spiritual but not in an institutional, religious kind of a way. In Catholicism, we're surrounded by these images of martyrdom and doing penance and doing some suffering to achieve what you're trying to achieve. And I certainly embedded that in my psyche and I have lived that very effectively.

The 'New Yorker' asked me to shoot a story on climate change in 2005, and I wound up going to Iceland to shoot a glacier. The real story wasn't the beautiful white top. It ended up being at the terminus of the glacier where it's dying.

The cumulative effect of each person making a change in his or her own life will make a difference.

I've got at least two major project ideas that I've been chewing on for several years in my head and I've been trying to resist them both. But I have learned over the years that when they don't go away and they're still in there, you probably have to resign yourself to the fact that you're going to do something about them.

Early in my career I discovered that there was something really special about photographing at night that places your mind on the surface of the planet. You’re no longer just a human being walking around in the regular world. You’re a human animal striding around on the surface of the planet that’s out in the middle of the galaxy. We as a culture, we’re forgetting that we are actually natural organisms and that we have this very deep connection and contact with nature. You can’t divorce civilization from nature. We totally depend on it.

There is a glacier in Iceland, Solheimar, which has retreated a great deal, and every time I go back there and see what's not there any more, it does something to the heart. It makes you realise it's possible for a gigantic natural element to just disappear.