"The world now has a work program, with timetables," he said in a statement Sunday. "While the long negotiations in Poland showed there are many tough talks ahead of us, the determined diplomacy of the U.K. and European Union achieved our aims, building alliances with our friends across the world."
The two-week U.N. Climate Change Conference in Warsaw concluded Saturday with an agreement to work toward a universal climate change agreement by 2015. Parties to the conference also agreed to work on ways to cut emissions and to address damage caused by climate change in developing countries.
European Commissioner for Climate Change Connie Hedegaard said the Warsaw conference proved there's a tough road ahead before the 2015 climate summit in Paris.
"For sure there will be faster and less bumpy ways to Paris but now the journey has started," she said in a separate statement Sunday. "We must make it there."
Sierra Club Executive Director Michael Brune said devastating summer floods in Colorado and deadly Typhoon Haiyan, which left more than 5,000 people dead in the Philippines, suggest action is needed now on climate change.
"We still have time to act to curb this crisis, but the window is closing quickly -- and we can't afford any more missed opportunities," he said in a statement Saturday.
Notable deaths of 2014 [PHOTOS]