Climate change is by definition a global challenge, and in his new book, “How to Avoid a Climate Disaster,” Bill Gates describes solutions that require an all-hands response including government, companies, institutions and individuals.

But as one of the world’s wealthiest people, an outspoken booster of tech innovation, the largest private owner of U.S. farmland, and someone who admits to having a Paul Bunyan-sized carbon footprint, Gates is also taking steps personally to help address greenhouse gas emissions.

He created Breakthrough Energy, an umbrella organization that includes a suite of investment, innovation and policy initiatives; is the founder of TerraPower, a company developing next generation nuclear power and energy storage; and has committed to offsetting his carbon emissions through the purchase of green aviation fuel and paying for direct-air carbon removal.

In the book, Gates also shares what other individuals can do to fight climate change.

But even with Gates’ increasing investments in climate-related initiatives, critics point to shortcomings in his actions, such as his foundation’s struggles to make good on his commitment to divest from fossil fuel interests and his recent investment in a private jet company.

In a recent interview about his book, I asked Gates how he viewed his role in the climate crisis, the status of TerraPower and his thoughts on geoengineering — the controversial strategy of helping cool the planet through man-made alterations of the atmosphere. Here are five takeaways from that conversation:

He’s doing more on climate, but is still focused on global health through the Bill and Melinda Gates Foundation.

“That’s where we’re expert — our malaria team, our vaccine factory team — and that’s where we’re going to stay committed,” Gates said. “And the returns on that, the impact of that, is phenomenal. It also happens that as kids grow up more healthily, their parents choose to have less kids. And so between improving health and getting voluntary family planning tools out there, there is a connection with climate.

Also, our foundation, because of our agriculture work, is the biggest funder of climate adaptation. And that involves, in many cases, giving better seeds to these subsistence farmers so they can deal with drought and floods and higher temperatures.

…The foundation, through its health and reproductive health and agriculture work, it’s helping with climate, but that’s not the primary lens that that foundation money is spent on. It’s spent on saving lives, which is still, I think, a super, super important thing.”

While massive, Gates’ wealth — currently estimated at about $124 billion — can’t fix global warming.

“In the case of climate change, even the money that I have, if it was all applied in this direction — I put in $2 billion so far and I’ll put in another $2 billion over the next five years — that’s not enough to solve it. The role of high-risk investing and philanthropy and creating programs like [Breakthrough Energy’s] Fellows and Ventures and Catalyst … the role of philanthropy is to start things out, but it’s really government policy [that] has to carry this one.”

He has made limited investments in geoengineering, and that might be it.

“Geoengineering, we don’t know enough about what the side effects of that would be, and so it is interesting. And at the very least we should understand the problems so that nobody goes and does it unilaterally, because the atmosphere is this important shared resource.

In some extreme case, if things got a lot worse quicker than we expect, you might use it to buy yourself 10 or 20 years of the negative effects. But even then, getting the right type of government consensus on whether to do it would be difficult. Getting the people in the lab to figure out some of what works, what we don’t understand about global weather effects, I think that is constructive, but it’s very small money. Nothing compared to what I’m putting into other climate areas.

I certainly wouldn’t want to [pursue geoengineering projects] alone. I’d want to feel like there were at least some countries and a broad set of scientists and other people, otherwise it’s kind of like a mad scientist-type insanity. I feel like I’ve done my part to seed that field a little bit, and if others want to come in, fine. I don’t see myself going up dramatically.”

Widespread, green-tech advances in transportation, electricity, agriculture, construction and heating and cooling systems are next-level difficult, and Gates is studying up on innovation.

“If you just look at what’s happened in the chip and software and internet area, if you think anything like that can happen in the physical economy, that would confuse you. That type of speed of improvement and cost reduction, there’s no other domain like it. In fact, even in medicine, that moves way more slowly than the digital world. Even there, in 10 years time, you can do some very dramatic things. And that’s a very hopeful space.

But now we’re talking about a part of the economy that’s physically the largest. Very little R&D, very little change over the last few decades. And yet we’re saying in 30 years, we’re going to change it very, very dramatically. So it’s certainly way harder than the advances that have taken place in other areas.

I do think that the template of accelerating innovation by finding smart people and having risk capital and funding basic R&D and creating market-based price signals, I think those apply very much. I’ve had to learn about these new areas, reading a lot of books and meeting a lot of experts. But my sense of how you drive innovation is part of what I’m bringing to this, suggesting that we can have a plan to go along with the goal and the energy that the advocates are putting out.”

Gates is bullish on nuclear and eager for his Bellevue-based company TerraPower to build a demo plant.

“Congress created a program, the Advanced Reactor Demonstration Program, and TerraPower competed in that and won a large award for the $4 billion demo plant. And so over the next five years, that’ll get built, and it’ll show people the economics and the safety.

It’s the only from-scratch reactor design that’s been done going back to the 1950s, where we can use digital tools to simulate any problem and really optimize all these components. Because nuclear power, despite all the waste and safety and proliferation concerns, the main reason it’s failing right now is that the reactors have gotten so costly to build. They’re just not competitive, particularly in a place where natural gas is so incredibly inexpensive.”

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