This summer, Bill Gates huddled in London with representatives of some of the world’s wealthiest people, including the Amazon founder, Jeff Bezos, the SoftBank founder, Masayoshi Son, and Prince al-Waleed bin Talal Prince of Saudi Arabia.They were evaluating their joint investments in companies that could help the world combat climate change. Among the businesses in their portfolio, four stood out as having a particularly audacious goal: They were working to strip carbon dioxide from the atmosphere, for a profit.As countries around the world continue to pump planet-warming pollution into the skies, driving global temperatures to record levels, the financial world...