A UN environmental agency said on Tuesday that nations have the chance to deliver almost 60 percent of the emissions reductions needed to keep global temperatures under a 2-degrees-Celsius rise.

But according to a report launched on Tuesday by the UN Environment Program (UNEP), nations will achieve that only if the pledges made last year in Copenhagen are fully met.

These are among the findings of a new report compiled by UNEP and jointly authored by over 30 leading scientists from numerous international research institutes.

The report was convened in conjunction with the European Climate Foundation and the National Institute of Ecology-SEMARNAT, Mexico.

The findings, launched in advance of the UN climate convention meeting in Cancun, Mexico, spotlight the size of the "emissions gap" between where nations might be in 2020 versus where the science indicates they need to be. "The results indicate that the UN meeting in Copenhagen could prove to have been more of a success than a failure if all the commitments, intentions and funding, including fully supporting the pledges of developing economies, are met," Achim Steiner, UN under-secretary general and UNEP executive director said. "There is a gap between the science and current ambition levels. But, what this report shows is that the options on the table right now in the negotiations can get us almost 60 percent of the way there. This is a good first step."

It is estimated that, in order to have a "likely" and cost- effective chance of pegging temperatures to 2 degrees Celsius or below over the 21st century, global emissions will need to have peaked within the next 10 years and be around 44 gigatonnes of CO2 equivalent in 2020.

The report, whose compilation was led by the UNEP chief scientist, finds that under a business-as-usual scenario, annual emissions of greenhouse gases could be around 56 gigatonnes of CO2 equivalent by 2020. As a point of reference, global emissions were estimated to be around 48 gigatonnes in 2009;

The report finds that fully implementing the pledges and intentions associated with the Copenhagen Accord could, in the best case identified by the group, cut emissions to around 49 gigatonnes of CO2 equivalent by 2020. "I encourage all parties to make good on their national mitigation pledges, and to further progress within the negotiations as well as through strengthened efforts on the ground to curb emissions," UN Secretary-General Ban Ki-moon, said. "There is no time to waste. By closing the gap between the science and current ambition levels, we can seize the opportunity to usher in a new era of low-carbon prosperity and sustainable development for all."