China and the U.S. announced on the eve of the Summit that they had ratified the Paris agreement on cutting climate-warming emissions, marking a major step toward the enactment of the pact as early as the end of the year and setting the stage for other countries to follow suit. China and the U.S. are he world’s two biggest emitters of greenhouse gases. “Just as I believe the Paris agreement will ultimately prove to be a turning point for our planet, I believe that history will judge today’s efforts as pivotal,” U.S. President Barack Obama said after he and Chinese President Xi Jinping handed ratified documents to UN Secretary-General Ban Ki-moon. “With China and the United States making this historic step, we now have 26 parties in the UN Framework Convention and 39% of global greenhouse gas emissions accounted for,” Ban said. Although the Paris deal was signed in the French capital in December, it will come into force only after at least 55 countries accounting for at least 55% of global greenhouse gas emissions join the accord. Ban urged other leaders to show leadership by accelerating their domestic ratification process. The accord signed in Paris aims to limit global temperature increases to 2 degrees Celsius, and 1.5 degrees if possible, compared with pre-industrial levels.