United Nations Secretary-General Ban Ki-Moon is challenging more than 100 world leaders to set a new course for a warming world and reverse the rise of heat-trapping gases.

Tuesday's one-day climate summit at the annual United Nations gathering of world leaders is a forum for non-binding pledges. It is designed to lay the groundwork for a new global treaty to tackle climate change due at the end of next year.

Ban said the world is facing an unprecedented challenge. He said Earth needs all hands on deck to weather the storm of climate change.