The EU's aim is to limit the rise in average global temperatures to two degrees Celsius above pre-industrial levels, and it will commit to cut greenhouse gas emissions by 20 percent by 2020, from 1990 levels, to do so.

But green organisations and the European Parliament, citing scientists and the United Nations, say the EU must reduce emissions of the gases that cause global warming by 30 percent by 2020 to realise that goal.

In a document drafted for their summit, starting Thursday, EU leaders will urge developed countries to "take the lead by committing to collectively reducing their emissions in the order of 30 percent".

However the bloc only "endorses an EU objective of a 30 percent reduction ... provided that other developed countries commit themselves to comparable emission reductions."

And for environmental organisations, therein lies the rub.

"Friends of the Earth has condemned this double standard -- a 30 percent reduction is needed for the EU to meet its own objective of keeping global temperature increase below two degrees Celsius," the group said in a statement.

The EU will make a "firm independent commitment" to reduce emissions by at least 20 percent by 2020 but the group says this will ultimately send the wrong signal to those developed countries Brussels claims to want to encourage.

"Adopting the lower target for the EU makes it unlikely that countries like the USA and Australia will come forward suggesting a target of 30 percent for themselves," it said.

To back up its case, Friends of the Earth noted that the first phase target for emission cuts under the Kyoto climate change protocol only ended up being half of what the EU was pushing for.

Greenpeace agrees.

"Experience suggests that international negotiations have a lowering effect on targets," it said. "We know and they know what needs to be done -- EU leaders should commit to a 30 percent emission cut by 2020."

The group noted that only Denmark and Sweden publicly back this goal.

The two-degree temperature rise appears to be a vital threshold.

According to the United Nations, 11 of the 12 last years have been among the hottest since 1850, when records on global surface temperatures began.

Temperatures have risen three quarters of a degree since the second half of the 19th century and the rate of temperature increase in the last 50 years is double that of the last 100 years.

In a recent climate report, Christian Aid noted that a two-degree temperature increase could cause up to 80 percent of crops to fail in southern Africa and force 150 million people to flee Asia's coastal regions.

Even the European Parliament, in a declaration last month marking the second anniversary of the Kyoto Protocol's entry into force, has said that the 30 percent figure must serve as the basis for EU policy.

"This is the bare minimum of what we must aspire towards," said British Greens MEP Caroline Lucas.

"Scientists have stressed that industrialised countries must reduce their emissions by at least this amount if we are to effectively tackle the climate crisis we are facing," she said.

The EU leaders will also have to go beyond simply agreeing on targets and translate their ambitions into actions.

"They must also go through the much more demanding process of getting a detailed agreement on who will do what," the European Policy Centre think-tank commented this week.

"The proposed targets will only be credible when it is clear how member states and different sectors of the economy will deliver what is required of them."

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