The United States ratified this. See the Congressional Record.

Matter is discussed in the post mortem on the Copenhagen Climate Summit on Charlie Rose:

This treaty includes contributions from developed nations to a fund (“Green Climate Fund”) which is intended to help move developing nations to renewable energy.  The obligation remains, although we have contributed nothing, and the House is trying to prohibit such contributions despite the fact that the Constitution says signed and ratified treaties are as binding upon the United States as any other law.

The history of this failed commitment on the part of the United States is ably described by Lattanzio.  Apparently, the United States isn’t even participating in discussions.