The first official draft blueprint for a deal at the UN climate talks sees targets of limiting global warming to 1.5 or 2.0 degrees Celsius (2.7 or 3.6 degrees Fahrenheit), according to a document seen by AFP on Friday.
The lower temperature is embraced by small island states and many African nations badly threatened by climate change.
The higher target has been supported by rich industrialised nations and emerging giants such as China, India and Brazil.
The temperatures relate to a total rise in warming over pre-industrial times.
The draft is to be submitted to environment ministers from around the world, with the goal of having it endorsed at a summit on December 18.
The talks are taking place under the 194-nation UN Framework Convention on Climate Change (UNFCCC).
If all goes well, a political agreement in Copenhagen would be followed by meetings next year to flesh out key details.
The envisioned global pact would take effect from 2013, after current pledges expire under the UNFCCC's Kyoto Protocol.
The proposed draft is put forward by the Ad-hoc Working Group on Long-Term Cooperative Action, or AWG-LCA, one of the two negotiating pools in the 12-day talks in Copenhagen.
Its task is to spell out a "shared vision" for combating climate change in the decades to come.
The text carries many brackets, which denote disagreement.
On the question of a target for warming, it reads:
"Parties shall cooperate to avoid dangerous climate change, in keeping with the ultimate objective of the Convention, recognizing [the broad scientific view] that the increase in global average temperature above pre-industrial levels ought not to exceed [2 C] [1.5 C]."
The draft text leaves open three possible targets for the overall reduction of global carbon emissions by 2020, compared with 1990 levels: by 50 percent, by 80 percent and by 95 percent.
Industrialised countries favour the 50 percent goal, while major emerging economies led by China have baulked at any such target unless it is made clear that rich countries will assume the near totality of the burden.
For rich countries, which acknowledge their historical responsibility for global warming, the bracketed options for CO2 cuts by 2050 in the text range from 75-85 percent, "at least 80-95 percent", and "more than 95 percent", all measured against the same 1990 benchmark.
(c) 2009 AFP
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