Ambitious global targets to reduce greenhouse gas (GHG) emissions could potentially keep the Earth's temperature from rising to two degrees Celsius above pre-industrial levels, said a panel of scientists working with the United Nations Environmental Programme (UNEP) on Thursday.

The group presented its "Emissions Gap Report," a study by scientists from 25 leading institutions in 15 countries and headed by  UNEP, the European Union's Climate Fund and Mexico's National Institute of Ecology (INE). The report aims to examine various emissions reduction targets outlined by 85 nations in the Copenhagen Accord drafted last year to influence discussions at the COP16/CMP6 conference in Cancun.

UNEP's chief scientist Joseph Alcamo, said that emissions need to be around 44 gigatons (Gt) of carbon dioxide equivalent by 2020 to prevent global temperatures from breaching a dangerous level of warming. Failure to act could raise levels to 56 Gt, creating a gap between actual levels and targets equal to the total amount of GHG emissions from the world's energy supply sector.

"On one hand, the glass is half empty, in that there is going to be a gap the size of the Grand Canyon between temperature targets and expected emissions if we do not act immediately," he said.

"On the other hand, the glass is also half full, because we found in our study that issues being considered on the negotiations have to do with low versus high ambition pledges and rules for complying with pledges have the potential to greatly narrow this gap, to considerably narrow this gap."