AFP: The United Nations’ climate change chief on Thursday urged people around the world to join in a "global work party" this weekend that is part of a growing grassroots movement to curb greenhouse gases. More than 7,000 events to fight climate change will be held in at least 180 countries around the world on Sunday, with the day gaining massive support largely through 350.org, tcktcktck.org and other Internet-based groups. "I congratulate you on your work and I want to offer my …