In addition, the report shows that the way in which the pledges are implemented - in other words how, for example, the accounting rules are set through the negotiations - can be almost as important as the big headline figures of the pledges themselves.

In other words, the rules underpinning the emissions reduction matter as much as the pledges. "This still leaves a gap of perhaps 5 gigatonnes of CO2 equivalent - a gap that could be bridged by higher ambition on CO2 by developed and developing countries perhaps complimented by action on a range of so-called non-CO2 pollutants such as methane from waste tips to black carbon from the inefficient burning of biomass and animal wastes," said Steiner.

The assessment, entitled The Emissions Gap Report: Are the Copenhagen Accord pledges sufficient to limit global warming to 2 or 1.5°C?, is the work of over 30 researchers from 25 centers in countries including Australia, Austria, Belgium, Brazil, China, Denmark, Germany, India, Japan, Mexico, the Netherlands, New Zealand, Switzerland, Britain and the United States. "The report underlines both the feasibility of emission reductions and the importance of international cooperation to raise the current inadequate level of ambition," Christiana Figueres, executive secretary of the UN Framework Convention on Climate Change (UNFCCC), said.

"Governments meeting at the UN Climate Conference in Cancún will need to both anchor the pledges they made in Copenhagen in the UN context and to work swiftly to agree ways to reduce emissions so that the world has a chance of staying below a 2 degrees Celsius temperature rise."

The report also assesses in an annex the individual pledges of more than a dozen key countries ranging from India to Russia and the United States.

The various scenarios include estimated emissions in 2020 if nations were to fully implement their most ambitious pledges versus the emissions in 2020 if nations meet only their minimum targets.

Many developing countries before, during and after Copenhagen and including South Africa, Indonesia and Mexico, have made pledges which are conditional on the action of others - in particular the provision of international climate finance.