In June, Pope Francis released his forceful climate encyclical using points that you made to him in your pitch.
A few of us [in the Pontifical Academy of Sciences] organized a meeting on sustainability for May 2014. You'd think we would come up with profound technological ways to fix the problem. Instead, the main conclusion [was that] to solve climate change requires a change in attitude toward nature and toward each other. Then I had to brief Pope Francis.
Normally, when you have an audience with the pope, it's in [a] breathtaking hall. I was waiting outside. I saw someone coming out of this small car, and it was Pope Francis. I was told I have a maximum of two minutes, two sentences, to come up with all he needs to know.
What did you tell him?
First, I said we have the most distinguished scientists and philosophers in the world concerned about climate change. The second sentence was that while most of the pollution is coming from the wealthiest 1 billion people, the poorest 3 billion are going to suffer the worst consequences. For him to hear this coming from scientists should have been like music, because he talks about the poor.
He said, "What should I do?" I told the holy father, "If you can, in your speeches, ask people to be better stewards of the planet. They will listen to you."
It's from that meeting I got my "aha" moment, that science and religion can come together on the environment because we both want the same thing: protecting the planet. There's none of the tension between science and religion on this particular topic.
Why is that important?
Ultimately I think we'll have top-down support from all the nations. What we don't have is bottom-up support from people. So if this is taught in every church, every mosque, every synagogue, every temple, the problem is solved. Catholic institutions have a tremendous reach, and in Africa and south Asia, that's where most of these 3 billion live. As a scientist, I have no authority to talk about behavioral change, but the faith leaders have that authority. We have to draw them into this to help us fight this war.
Poor countries complain that rich nations have already got theirs — and they got it by polluting. They say it's unfair to impose restrictions that could keep them from doing the same.
I ask the poor nations, "What are you going to do if sea level goes up by six feet and your people are flooded? Are you still going to do this blame game? It's not going to help. You have to roll up your sleeves and get into the solution and try to persuade the developed nations that your survival is at stake."
[The U.N. fund underwritten by the developed nations] should be promoting clean energy access for them, both to protect them against climate change but also for our self-interest, because if they get on the fossil fuel ladder like us, then there's no hope to save the climate. We hope and pray that they're going to start enjoying a decent standard of living soon, but if that is using fossil fuels, it would be the wrong way for the planet.
You speak about bending the curve, not having to halt greenhouse-gas trends immediately.
Everything we're seeing is on an upward curve: carbon emissions, our population, our consumption of natural resources. People are thinking we've got to change everything rapidly. I don't subscribe to that. Bending the curve [means] we need to make incremental changes.
Isn't there a single tipping point?
Different regions, different nations, even different cities would face different tipping points.
Take California and the drought. It's not one or two things which caused it: snowpacks melting early, the evaporation of moisture [when] each degree rise in temperature increases the loss of moisture from 7% to 15%, which means trees, lakes, oceans are losing moisture. It's the vicious cycle between the natural variation of Pacific rainfall and underlying chronic loss of moisture from everything — that's a tipping point.
In India, where I was born, the tipping point is going to be the monsoon; [and it] is already changing.
The tipping point is a relevant metaphor, but public perception could say, "My God, we've gone over the tipping point, there's nothing we can do, we might as well sit and enjoy the rest of the time we have."
That could be a problem.
Are we not willing to change?
If you look at times when we have made changes, it's only in the face of major catastrophes, [like] when we saw Antarctic ozone [and phased out chlorofluorocarbons and hydrochlorofluorocarbons]. I go back to what Churchill said: "You can always count on Americans to do the right thing — after they have tried everything else."
There is an argument that anything less than top-down global solutions won't work. You believe in scaling up.
We have been on this top-down [approach] for 21 years, and it's not working because of a lack of public support. I keep getting asked, what's the solution?
The University of California's population is a half-million on 10 campuses. If we can go carbon neutral in 10 years, that's a spectacular demonstration that this thing can be done on scale. California is [embracing] 40% reduction [below 1990 levels] by 2030. That would be a particularly spectacular demonstration because we are the seventh or eighth largest economy. Our GDP is the highest among the states. This doesn't kill the economy — if anything, it prospers.
Is climate change like driving a car off a cliff — by the time you see the edge, it's too late?
It's definitely not too late now. I agree that we are driving very fast toward the cliff. Scientists like me now can see that cliff; the general public would see that cliff in 10 years, but if you wait for 10 years, the actions you have to take are so drastic, we need to do it now.
What is on your wish list for Paris?
That we have a piece of paper signed by all 190-plus nations, a mandated agreement that they all agree to cut carbon pollution and bend that curve. I personally don't care how much – 5%, 10%, 30%. I see that as a technical detail. We need a document everyone's signed that says climate change is important, it's caused by human activities, and everyone is committing to it. That's the foundation on which we build. I don't want us to come back empty-handed, that if some nation doesn't commit to X% reduction, then we start from scratch.
This interview has been edited and condensed.