Carbon dioxide emitted by energy use hit a record high last year, dimming prospects for limiting global warming to two degrees Celsius, the International Energy Agency (IEA) said Monday.
Breaching the 2.0 C (3.6 degrees Fahrenheit) threshold sharply increases risk of severe climate impacts, including flooding, storms, rising sea levels and species extinction, scientists have warned.
"Energy-related carbon-dioxide (CO2) emissions in 2010 were the highest in history," the Paris-based IEA said in a statement posted on its website.
After a dip in 2009 caused by the global financial crisis, emissions climbed to a record 30.6 gigatonnes (Gt), a five-percent jump from the previous record year in 2008, the agency said.
Moreover, 80 percent of projected greenhouse gas emissions in 2020 from energy sources are "locked in" as they will come from power plants already operating or under construction.
"This significant increase in CO2 emissions and the locking in of future emissions due to infrastructure investments represent a serious setback to our hopes of limiting the global rise in temperature to no more than 2.0 C (3.6 F)," said IEA chief economist Fatih Birol.
UN climate change talks have agreed that average global temperatures should not increase by more than 2.0 C (3.6 F).
To achieve this goal, long-term concentration of greenhouse gases must peak at about 450 parts per million (ppm) of carbon dioxide (CO2) equivalent, barely five percent more than in 2000, scientists say.
This target will slip beyond reach if global energy-related emissions in the year 2020 exceeds 32 Gt, the IEA has calculated.
The rise in emissions over the next decade must be less than the jump between 2009 and 2010, the agency cautioned.
"Our latest estimates are another wake-up call," said Birol.
"The world has edged incredibly close to the level of emission that should not be reached until 2020 if the 2.0 C (3.6 F) target is to be attained."
The UN's top climate official said the figures underscored the urgency for political action.
"The IEA estimates ... are a stark warming to governments to provide strong new progress this year towards global solutions to climate change," said Christiana Figueres, executive secretary of the UN Framework Convention on Climate Change (UNFCCC).
UN climate talks, resuming in Bonn next Monday, remain deadlocked on how to achieve the 2.0 C (3.6 F) target.
Even the Kyoto Protocol, whose first round of emissions-cutting pledges for rich nations expires at the end of 2012, may be in jeopardy as key nations say they do not favour renewal.
"The figures mean that the world is very far from achieving the goal of preventing a temperature rise of more that two degrees Celsius," EU climate commissioner Connie Hedegaard said in a statement, calling on other nations to set binding targets and emissions trading schemes as has the European Union.
Emerging countries say emission limits will stunt their development and argue that only rich economies can afford green technology which can boost living standards and cut emissions.
The IEA estimated 40 percent of global emissions in 2010 came from the Organisation for Economic Cooperation and Development (OECD) club of advanced countries.
But these only accounted for a quarter of the annual emissions growth. The rest came came from rapidly developing countries, led by China and India.
On a per-capita basis, OECD countries emit on average 10 tonnes, compared with 5.8 tonnes for China, a voracious burner of coal, and 1.5 tonnes in India.