The first happened at the end of November, when a group of billionaires led by Bill Gates, Mark Zuckerberg, and Jeff Bezos announced the creation of a $20 billion fund to back clean-energy research. On the same day, a group of 20 countries, including the United States, the United Kingdom, Germany, India, China, and Brazil, agreed to double their investment in green energy, to a total of $20 billion a year.