Following in the footsteps of the European Union, Japan ratified the Kyoto Protocol on climate change today, becoming the 73rd country to commit to curbing greenhouse gas emissions. Japan had previously waffled on ratification, especially after the Bush administration backed out of the treaty, but public pressure won out and the country’s upper house of parliament voted unanimously in favor of ratification on Friday. The Japanese cabinet sealed the deal today. Fifty-five countries representing 55 percent of developed nations’ carbon dioxide emissions must ratify the treaty for it to come into effect; with Japan’s participation, the agreement has support from developed countries responsible for 36 percent of gases. When (and if) Russia signs on, the 55 percent target will very likely be met — but not as easily as it would have been with the help of the U.S., the world’s largest polluter at 36.1 percent of all greenhouse emissions in 1990.