That the G8's newly stated "goal" of a 50-per cent reduction in carbon emissions by 2050 is deliberately vague in its wording almost goes without saying. No-one really expected the leaders of the world's major economies to be taking the lead on climate change, especially with George W Bush still in the White House.

Politically, however, today's G8 statement on climate change is a carefully worded text that gives each G8 delegation something to go home with even it fails to give any satisfaction to environmental campaigners.

Last time around, in Heiligendamm, Germany, the G8 nations skated fairly quickly over the issue of climate change, but agreed, in the chairman's final statement, to "consider seriously the decisions made by the European Union, Canada and Japan which include at least a halving of global emissions by 2050".

This time, on the Japanese island of Hokkaido, they issued a lengthy statement on what the world needs to do to combat the threat of global warming, including the development of clean technologies and new market mechanisms.

But they moved only fractionally closer to a binding target on reducing carbon emissions, instead putting the onus on the negotiations for the United Nations Framework Convention on Climate Change (UNFCCC), the successor treaty to the Kyoto Protocol which is due to be wrapped up at a UN summit in Copenhagen next year.

Today's communique stated: "We seek to share with all Parties to the UNFCCC the vision of, and together with them to consider and adopt in the UNFCCC negotiations, the goal of achieving at least 50 per cent reduction of global emissions by 2050, recognising that this global challenge can only be met by a global response, in particular, by the contributions from all major economies, consistent with the principle of common but differentiated responsibilities and respective capabilities."

By putting the onus onto the UN, the communique allows Western European nations to take the lead ahead of the Copenhagen summit in the push for stronger emissions targets. The phrase "at least" allows them to argue that a 50-per cent reduction by 2050 should be seen as just a starting point.

But even that reduction is just a "goal", not a binding target - which would not have been accepted by either the United States or Canada, both of which are major energy producers and consumers.

Environmental campaigners said that the communique glaringly misses out any mention of two key aspects to a deal: an interim target, for 2020 or 2030 for example, and a clear statement of the base year from which the reductions will be counted.

The Kyoto Protocol, which expires in 2012, used the base year of 1990, which at the time was seen as advantageous for the Europeans and difficult for the Japanese, who had already made energy efficiency gains in the 1990s. Japan argued at this year's G8 for a new base year of 2006, which would make it easier to meet any future targets.

Green groups and aid agencies reacted with disappointment to the latest G8 text, including its use of committed aid funding to help developing countries tacked climate change.

“The G8’s endorsement of a tepid ’50 by 50’ climate goal leaves us with a 50/50 chance of a climate meltdown," said Antonio Hill, a spokesman for Oxfam.

John Sauven, executive director of Greenpeace, added: “The G8 leaders have failed the world again. We needed tough targets for the richest countries to slash emissions in the next 100 months, but instead we got ambiguous long-term targets for the world in general.

“The G8 could and should have ruled out the scores of new coal-fired power stations set to be built across the industrialised world, threatening any hope we have of beating climate change. Instead we got a festival of vacuous back-slapping that bore no relation to the scientific reality we face as inhabitants of a warming world. Thank God this was Bush’s last G8.”

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