Israel's prime minister and the Palestinian president, in France for the climate summit, met and shook hands for the first time in years.
A photograph shows Benjamin Netanyahu and Mahmoud Abbas shaking hands and smiling on the sidelines of global climate talks outside Paris on Monday. It was not immediately clear if they had agreed to meet or if they spoke.
US mediated peace talks between the sides collapsed early 2014 and the two leaders have not met in years.
Meanwhile, leaders of small island nations pleaded for their survival, asking bigger countries to do more to cut emissions and help threatened nations cope with rising seas and wilder storms blamed on man-made global warming.
Peter M Christian, president of the Pacific nation of Micronesia, called on UN secretary-general Ban Ki-moon to declare a worldwide state of emergency.
Mr Christian said: "The challenge is to save ourselves, not someone else, but ourselves."
The prime minister of the Pacific country of Tuvalu, Enele Sosene Sopoaga, added that "any further temperature increase will spell the total demise of Tuvalu."
They spoke in Paris on the opening day of high-stakes climate talks aimed at reaching a global compromise to cut emissions long-term.
Bill Gates said he and other investors are pledging seven billion US dollars (£4.6 billion) for research and development of clean energy, and that they are hoping to get others to pitch in more in the coming days.
The Microsoft co-founder is announcing the investment as part of a larger initiative with world governments that are promising to double spending on renewable energy research.
Mr Gates told reporters that he is hoping to see more investors sign on "possibly this week." The money is being raised by individual wealthy investors and the University of California.
He said he has warned potential investors that new energy technologies take longer than IT or biotech to launch.
The fund will support a wide range of technologies, Mr Gates said - "biofuels, carbon capture, high wind, fission, fusion - we're unbiased but it has to be clean and possible to scale up cheaply".
And Mr Putin said Russia is ready to cut its greenhouse gas emissions by almost one-third over the next 15 years compared with 1990 levels - although the fall in Russia's economy since 1990 means that it could still increase its current emissions.
He said that by 2030 Russia is ready to bring its greenhouse gas emissions to 70% of their level in 1990.
Mr Putin also said that a future global climate deal must include commitments from both developing and developed countries.