VOA慢速英语:World Leaders to Sign Climate Agreement on Earth Day

sustainable - adj. involving methods that do not completely use up or destroy natural resources

vulnerable - adj. easily hurt or harmed physically, mentally, or emotionally

greenhouse gas emissions - n. gases released into the air that cause heat to be trapped and heat the planet

enforceable - adj. to make sure that people do what is required by (a law, rule, etc.)

global - adj. of the whole planet