The Group of Eight industrialised nations on Tuesday endorsed halving global emissions of greenhouse gases by 2050 and called on individual countries to set goals reducing their own emissions much earlier, Japan's prime minister said.
"After today's G8 summit we agreed to set the aim for a reduction of the entire global emissions of gasses to 50 percent by 2050 as a target to be taken up by the entire world," Yasuo Fukuda said.
Oil prices have hit record highs, roiling world economies, while rising food costs have triggered shortages and social unrest in Africa, South Asia and elsewhere.
The G-8 has also been under pressure to secure commitments by wealthy nations to push forward stalled UN-led talks on forging a new accord to battle global warming by the end of next year.
The G-8 countries; the United States, Japan, Russia, Germany, France, Britain, Canada and Italy, pledged last year at a summit in Germany to seriously consider the same target.
The Japanese hosts of this year's summit had hoped to solidify that commitment at the meeting in Toyako, northern Japan.
Environmentalists have argued the 50 percent reduction target was insufficient, and have clamoured for ambitious midterm targets for countries to cut emissions by 2020.
Such shorter-term targets, however, have been much more difficult to reach consensus on.
The United States, for instance, has argued that meeting an oft-cited goal of reducing emissions by between 25 percent and 40 percent by 2020 is unrealistic.
In a nod to such disagreements, Fukuda said the G-8 countries would set individual targets.
Philip Clapp, deputy managing director of Pew Environment Group, said a promise from the G8 on the 2020 target would trigger action by developing nations.
"A clear commitment on the part of the United States to engage in negotiations on a binding treaty with a clear midterm target of 2020 would bring developing countries into a position where they can agree to a long-term global goal," he said.
On Wednesday, the leaders of these countries will be joined by eight other big-polluting "major economy" nations that are not members, including China and India, to see if a wider agreement is possible.
Another international non-governmental organisation focussing on climate change was more critical.
"The failure to act on 2020 targets is a failure to take responsibility, and our members around the world feel that there is a childishness to not taking responsibility," Ben Wikler, the Campaign Director of AVAAZ said.