A failure of major economies to set a target for halving world greenhouse gas emissions by 2050 at a summit in Italy is a setback to any agreement at a December climate change conference in Copenhagen.

But a reference in draft documents by the Group of Eight and 17-country Major Economies Forum, whose members account for about 80 percent of global gas emissions, to limiting world temperature rises to 2 Celsius (3.6 Fahrenheit) above pre-industrial levels is a step that will -- if taken seriously -- force deep cuts.

They are running out of time toward Copenhagen, said Alden Meyer of the Union of Concerned Scientists. More than 190 nations are due to agree a U.N. climate pact in Denmark's capital.

It's progress to set a goal based on science, he said of the 2C target. But it's a missed opportunity if they don't set clear 2050 and 2020 targets about how to reach that goal.

The July 8-10 G8 summit, with a meeting of the forum on Thursday, was seen by many climate campaigners as a chance to break the deadlock over sharing the burden of curbing greenhouse gases in what could be a mini-blueprint for the U.N. treaty.

But at a meeting on Tuesday, China and India blocked calls by G8 nations to sign up for a goal of halving world greenhouse gas emissions by 2050. A text agreed overnight omits any reference to that target.

If this is now the result of the G8 talks, that would be really shocking, said Tobias Muenchmeyer of environmental group Greenpeace. He said G8 nations needed to set tough 2020 goals for themselves and promise finance for developing states.

It is disappointing that they haven't come further, said Kim Carstensen, head of the global climate initiative of the WWF International environmental group.

He said any slim hope for progress by the forum had been further trimmed by the departure of Chinese President Hu Jintao, who returned to Beijing because of unrest in northwestern China in which 156 people have been killed.

BARGAINING CHIP

The larger developing nations say the rich must first set far steeper cuts in their own emissions by 2020 and agree billions of dollars in funds to help the developing world move to renewable energies and cope with more frequent droughts, floods, heat waves and rising sea levels.

By refusing to set a 2050 goal, which would imply cuts by the developing world, they may want to keep back a bargaining chip before Copenhagen.

G8 nations have so far promised cuts in emissions that total about 10-14 percent below 1990 levels -- far short of the at least 40 percent demanded by developing states.

And a U.N. panel of scientists has outlined cuts of 25-40 percent below 1990 levels by 2020 to avoid the worst of global warming by developed nations, with developing countries making a significant deviation below projected rise in emissions.

Such cuts by 2020 are broadly consistent with a 2C goal.

If they take that 2 Celsius goal seriously, developed countries will have to deliver much more ambitious mid-term targets, and developing nations will have to start to act more, Carstensen said.

World temperatures have risen by about 0.7 Celsius in the past century and most experts say the 2C goal is looking out of reach unless there are deep cuts.

(Editing by Elizabeth Piper)

China India Global warming Climate