World leaders, including the developing nations, yesterday committed themselves only to "substantially reducing global emissions by 2050", but failed to agree a specific target, according to a draft of the communique due to be issued later today.

The draft states: "We recognise the scientific view that the increase in global average temperature above pre-industrial levels ought not to exceed two degrees centigrade."

The draft is due to be issued by the Major Economies Forum under the chairmanship of Barack Obama. The MEF contributes 80% of world emissions.

The lack of a substantive agreement, other than the desire to keep global temperatures down, leaves world leaders facing daunting negotiations to reach agreement at the Copenhagen conference in December, which is due to set the entire climate change framework covering the period from 2012 to 2050.

Developed nations, according to the draft, agree to work in the run-up to the UN Copenhagen conference in December "to identify a global goal for substantially reducing global emissions by 2050". In a weak reference to the need for interim targets for 2020 emission cuts, the draft simply states the global goal will be regularly reviewed.

The statement does not commit either developed or developing nations to the worldwide 50% cuts target by 2050 agreed by the G8 on Wednesday. The language agreed jointly on 2C in today's draft is exactly the same as that deployed by the G8 nations on Wednesday.

The draft statement also states that "the financial resources for mitigation and adaptation will need to be scaled up urgently and substantially and should involve mobilising resources to support developing countries".

But no figure is given for the scale of resources required in the communique. Green and aid groups suggest that as much as $150bn per year in additional funds will be required to help developing countries respond to the effect of climate change. A lot of this money would be privately funded green technology transferred to developing nations, or cash raised from the nascent carbon market.

They also derided today's draft statement, with Tearfund warning: "This rolling dialogue points to the opposite direction to urgency and must not continue. We now have to wait until the UN September meetings when the heads of state will gather once again."

The developing countries are refusing to commit themselves to specific target cuts at this stage partly because they do not know what proportion of the burden of cutting emissions will be taken in the interim.

Developing nations such as Mexico want the rich countries to commit themselves to 40% carbon cuts by 2020, against a baseline of 1990 levels, so that developing countries do not have to take responsibility for the industrialisation of the rich.