FACTBOX - How to judge success, failure at U.N. climate talks

(Reuters) - Talks on a new U.N. climate deal are bogged down before a Dec. 7-18 meeting of 190 nations in Copenhagen -- the following lays out how to judge success or failure.

Most clearly, the U.N. Climate Change Secretariat lists four "political essentials" for a successful new pact, with many details to be filled in later:

1) DEVELOPED COUNTRIES

-- "Ambitious emission reduction targets" for rich nations.

Scientists in the U.N.'s Intergovernmental Panel on Climate Change (IPCC) said in 2007 that developed nations would have to cut emissions by between 25 and 40 percent below 1990 levels by 2020 to avert the worst of climate change. So far, promises average 11 to 15 percent below 1990 levels.

"Pledges for mid-term targets by industrialised countries fall woefully short of the IPCC range," the Secretariat says.

The United States, the number two emitter behind China, may not agree carbon laws by December. That may make it hard for Washington to give a firm pledge at Copenhagen.

2) DEVELOPING NATIONS

-- "Nationally appropriate mitigation actions" by developing nations to slow the rise of their greenhouse gas emissions.