The world remains far away from meeting UN-backed goals on holding back climate change, setting the stage for major damage without more ambitious efforts to cut emissions, a study said Tuesday.

Scientists who support climate action said that China, the largest source of carbon blamed for rising temperatures, is on track to surpass its own targets but warned that its overall emissions are growing more quickly than thought.

The controversial UN-led Copenhagen summit in 2009 agreed to limit global warming to 2.0 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels, a goal some environmentalists say is already too timid.

At the latest UN talks underway in Panama City, the Climate Action Tracker, which aims to keep track of countries' efforts, found a yawning gap between governments' pledges and their track records when added together.

A study by the group found that the world at current rates would emit 54 billion tonnes of carbon dioxide or its equivalent in 2020, a gap of 10 to 14 billion tonnes with what is needed to meet the goals.

The planet is "very, very far away" from meeting the 2.0-degree goal, said co-author Bill Hare, a lead writer of the major 2007 UN scientific report on climate change and director at Potsdam-based research group Climate Analytics.

"We are heading towards a warming of well over 3.0 degrees at present unless there are major improvements in the pledges," Hare, who has advised environmental group Greenpeace, told a news conference.

Hare said that while even 2.0-degree warming is problematic, the higher rate puts the world at risk to major problems such as more frequent wildfires and rising sea levels -- a top concern for low-lying nations.

"The warming levels that we're heading towards -- 3.0 degrees -- could easily result in massive damage to vulnerable ecosystems from one end of the planet to another," Hare said.

"We would see, particularly in Africa, very dangerous threats to food production and availability if present agricultural practices don't change fast enough," he said.

The week-long talks in Panama aim to prepare for the upcoming conference of the UN Framework Convention on Climate Change in Durban, South Africa, where governments will face hard questions on future climate action.

The Kyoto Protocol's requirements to cut carbon emissions -- which apply only to wealthy nations -- expire at the end of 2012.

China, which has surpassed the United States as the top emitter, has resisted a binding international treaty but has pledged to reduce the amount of carbon it produces per unit of gross domestic product by 40 to 45 percent by the end of 2020.

The Climate Action Tracker said that China was poised to do better than its own target as it is taking action to save energy and switch from carbon-intense fossil fuels to wind and other renewables.

But the study said that China was meeting its own goals also in part because it had used conservative forecasts for economic growth.

China's efforts "constitute a major effort. That is very positive," said Niklas Hoehne, director of energy and climate policy at consultancy Ecofys.

"But still emissions are in total higher than expected before because of this rapid economic growth," he said.

In the United States, President Barack Obama has promised to reduce emissions by 17 percent from 2005 levels but faces staunch opposition from the rival Republican Party.

A number of Republicans question scientists' findings on climate change and say that major reductions in the use of oil and other fossil fuels would cause a new burden for the troubled US economy.

The Climate Action Tracker also expected "significantly higher" emissions than previously estimated from Brazil.

Brazil has pledged a 36-39 percent reduction in emissions compared with a scenario in which it does nothing. But recent Brazilian data show higher emissions at current rates from deforestation and other sources, the study said.