His role in sealing the deal offers a peek into how the inner circles of governments and industry intersect. It also underscores how a handful of the world’s wealthiest people can stand with heads of state to spotlight a social, economic and policy issue on the global stage. For Mr. Gates, the world’s richest person and co-chairman of the biggest private foundation, it is another sign of how his vast foreign aid operation and status as a technology icon have turned him into a uniquely influential global diplomat.

Mr. Gates was drawn into the effort after the June meeting with Mr. Hollande and separate discussions with White House staff members in the summer. Mr. Hollande and President Obama saw the tech mogul as a potential catalyst for achieving broad political and diplomatic goals at the climate conference. In particular, Mr. Gates’s renown in India as a tech founder and philanthropist gave the French and American governments a key emissary to get the Indian prime minister, Narendra Modi, on board with their climate goals.

Mr. Hollande and Mr. Obama agreed to work with Mr. Gates to assemble a coalition of governments to double their spending on energy research and development. For added heft, Mr. Gates volunteered to organize a group of billionaires to fund clean-technology start-ups. He reached out to his extensive network, including Jeff Bezos of Amazon, Jack Ma of Alibaba and Mark Zuckerberg of Facebook, all of whom agreed to participate.

Last week, on the opening day of the Paris meeting, Mr. Gates joined Mr. Obama and Mr. Hollande to introduce the coalition. It will commit 20 governments to doubling their renewable energy research budgets to a total of $20 billion over the next five years.

In addition, Mr. Gates and a group of other wealthy businesspeople agreed to invest at least $2 billion in clean-energy start-ups — with half the money coming from Mr. Gates himself. The group plans to finance companies that turn promising clean-energy concepts, some of which will originate in government labs, into viable products. Some of the companies will fail, Mr. Gates warned.