If he really wanted to do something useful, he ought to give money to the scientists working for a solution to climate change.
Euh.... he does. Billions.
For example, he had a team of physicists and engineers design a new generation of nuclear power plants, which is supposed to replace all current ones. Most of the current ones were designed in the 60s and 70s. With a pencil and a ruler.
The new design is also not wasteful. In fact, they can run on the nuclear waste of the old designs.
Back in 2015, he pretty much had a deal with china to build prototypes of these factories in China, as some sort of test case. And then Trump came to power and started a virtual war with China, after which the deal had to be stopped. And instead of building these power plants in the US, Trump preferred to double down on fossil fuels and even rebooted coal industries....
Guys like Gates and Musk are tech visionaries with the money and the brains to come up with very creative solutions to some of the world's biggest problems. But even with all their money and expertise, they can't do anything to turn things around without governments playing ball.
I always like to compare it to asbestos. Back in the day, this was a common material used in construction. Very common. Then it was discovered what its negative impact was on environment and health. Same with the cfk gasses which were found to damage the ozone layer.
The result was that, practically overnight, these things were simply outlawed. From one day to the next, I could no longer build a house that has asbestos in the roofing.
I could no longer buy a spray can that contained such gasses.
Why is it, that I can still buy fossil fuel cars?
Why is it, that cars under development right now and which won't even come out in the next 2 years, are still running on fossil fuels?
Would it hurt economically at first? Sure. But at the same time, it would open up IMMENSE economic opportunities. Big oil companies could shift their focus from oil to things like solar power, battery technology, hydrogen fuel, etc.
They won't do that as long as the billions and trillions keep rolling in due to being completely free in trading oil. But watch how fast they will manage to switch tracks once government tells them "the end".
IMO, not enough people are going to change how they act to affect climate change.
Having said the above, I think it is simply not realistic to "rely" on citizens of the world to "change their behavior" well enough as to turn climate change around.
As said, as long as fossil fuel cars are being sold and as long as they remain 2x, even 3x, as cheap as electric cars - people are going to keep buying fossil fuel cars.
People also aren't going to drive less. It is not realistic to expect citizens to cut their driving by 50% to 70%. It simply is not going to happen.
The human behavior that affects climate change is the total output of human society. And the root cause of it is the technology used. What you need to do is actually tackle the problem of "dirty technology" and replace it with "clean technology".
In this day and age, I shouldn't be able to buy a fossil fuel car. Just like I'm no longer able / allowed to use asbestos in the roofing of my house.
Instead of trying to convince me to stop driving.... just give me a cleaner car!