 Well, I think one of the most serious, if not the most serious, long-term problem that's facing humankind is the considerable risks of climate change. And we know that we essentially have to go to zero-carbon emissions, certainly by the end of this century, if there's a hope of containing the worst and controlling the worst of the risks of climate change. The challenge to go to zero-carbon emissions cannot be overestimated. How do you get clean energy is the issue. There has been great technical progress, wind, solar, hydro, other forms of energy. The prices are coming down and it's very exciting. I think, for example, in the United States, we can easily get to 50% renewable energy of the electricity. Then if you look at how do you get to 75%, how do you get to 100%, it becomes that last 25% becomes very, very difficult. We're used to turning the lights on and expecting the lights to go on when we flip the switch. So we need energy on demand. And so with energy on demand, there are two forms that we know of today. One is nuclear, one is fossil. When the wind stops for two weeks or a month or you just need the energy, you're not going to stop industry, you're not going to go up around in the dark. And so I think we need nuclear for the last 25%. Part of the transition to carbon free energy will rest on science and technology and innovation. I think the big push will come if we can get a battery that weighs maybe three times less and can charge not in two hours, but if you can put 120 miles in five minutes onto a car, then the game is over. This is what we need for electric vehicles really to go viral. By the end of the century, I would say that most transportation can be electrified, wherever possible trains should be electrified, personal transportation should be electrified. I'll be optimistic and likely by the end of the century, we will have liquid hydrocarbon fuels for airplanes that can be made in a clean way, not from traditional oil sources. I think that one of the best policy things that we could do is to put a price on carbon. I strongly favor a simple tax. It's less likely to be gained. You start very low, let's say $10 a ton of CO2, $15, and it marches slowly up over a period of 20, maybe 25 years. When you have that in place, companies like oil and gas companies say, aha, the full cost of doing business is now more incorporated into the cost of what we sell, and now we can decarbonize in a way that would be fair to our shareholders. I think all the major multinational oil companies in the world that I know of recognize the climate is changing. They recognize that human activity played a dominant role, if not really the major cause of this, and they realize that towards the end of this century, they've got to decarbonize their business, which means their business has to change. It's not a debate whether it's a risk or not. It's whether it's going to be bad, very bad, or catastrophic. The sea levels are going up by 25 or 30 feet. That means migration and evacuation. The top quarter of the population, I'm not worried about it. It's the bottom quarter that can't adapt, and that would be tragic.