(Copenhagen) President Obama and counterparts from three other nations have struck a broad deal on reducing greenhouse-gas emissions. Taking part in a UN global climate change summit in Copenhagen, Obama called the agreement with China, India and South Africa quote "significant." Obama cited progress, but warned of a long, hard road ahead. He said climate change threatens the entire world and said industrialized nations must "get off the sidelines" and engage in active discussions on solutions. After arriving in the Denmark capital at weeks end, Obama threw himself into a flurry of negotiations on stalled talks over climate change.