Countries gearing up for the next round of top-level climate talks have been warned the agreement hashed out in the dying minutes of the Copenhagen conference could lead to 3C warming or more.

The Copenhagen Accord could allow developed countries to emit more greenhouse gases than they would have if they did nothing new to combat climate change between now and 2020, says a new analysis.

New Zealand climate scientists say a report published in the scientific journal Nature today is a wake-up to world leaders, who will re-start negotiations in Cancun, Mexico in November.

It said that even if countries made the biggest cuts offered, they would be left with a task akin to "racing towards a cliff and hoping to stop just before it" to stop the world warming more than 2C.

The comments are in an analysis by 10 climate researchers at the Potsdam Institute, Climate Analytics and Ecocyfs in Germany, which estimates pledges made by countries since Copenhagen will result in global emissions rising 10 to 20 per cent by 2020.

Under the accord, rich countries' emissions by 2020 could be anywhere between a 6.5 per rise or 15.6 per cent fall from 1990 levels - a far cry from the 25 to 40 per cent fall scientists say is needed to have a good chance of keeping warming below 2C.

"Countries have said 'we want to limit warming to 2C' but their collective actions are entirely inconsistent with that long-term goal," said Victoria University climate researcher Andy Reisinger.

Scientists say dangerous climate change becomes more likely over 2C.

More than 100 countries, including New Zealand, have agreed to try to limit global warming to less than 2C and to re-consider the option of a 1.5C limit by 2015.

The Copenhagen accord includes voluntary emissions goals from 76 countries, which account for about 80 per cent of global industrial emissions.

Many targets (including New Zealand's 10 to 20 per cent reduction) are expressed as a band with an upper and a lower end.

The authors of the analysis said nations were likely to go for the lower end.