Fraught UN climate talks revealed growing frustration this week among vulnerable nations and observers with the political stance of emerging economies like China and India in the battle to stave off dangerous Earth warming.

As the global balance of economic and political clout shifts, the world of climate negotiations is no longer a simple standoff between developed and developing nations.

Some fear a growing divide within the developing bloc will see the voice of poor, climate-vulnerable nations increasingly drowned out, further complicating the quest for an Earth rescue plan.

"This year's talks have highlighted a growing divide between poor developing countries that stand to lose the most from the lack of action on climate change, and countries that seem willing to hold up progress for tactical reasons," summed up the Environmental Investigation Agency advocacy group.

China, India and Brazil led a charge at talks that ended in Warsaw on Saturday for recognition by the West of "differentiation" between developed and developing states when it comes to responsibility for curbing climate-altering greenhouse gas emissions.

With their growth powered by fossil fuel combustion, the developing world giants blame the West's long emissions history for the peril facing the planet today, and insist it carries a larger burden for fixing the problem.

Some fear this tit-for-tat exchange is removing the focus from the bigger picture.

"We need to get back to the spirit of Durban, which promised a truly multilateral approach with ambitious contributions from all," Tony de Brum, Minister-in-Assistance to the Marshall Islands President, told AFP.

The Pacific island state is one of many at risk of being engulfed by climate change-induced sea level rise.

'If we get it wrong, true poor countries will pay'

The Durban climate conference in 2011 had agreed on a new pact to be signed by 2015, for the first time binding all the world's nations to emissions curbs.

The goal is to limit average global warming to 2.0 degrees Celsius (3.6 deg Fahrenheit) over pre-Industrial Revolution levels.

On current emissions trends, scientists warn the Earth could face warming of 4.0 C or higher -- a recipe for catastrophic storms, droughts, floods and land-gobbling sea-level rise that would hit poor countries disproportionally hard.

Wealthy countries stuck to their guns in Warsaw, saying developing nations must do their fair share given that China is now the world's biggest emitter of CO2, with India in fourth place after the United States and Europe.

In the end, delegates agreed on a watered-down text referring to nationally-determined emissions cut "contributions" rather than "commitments".

"As the deadline (to 2015) draws near, many emerging economies realise 2015 poses a serious threat to their vested interests," said Liz Gallagher, senior policy adviser for the E3G renewable energy advocacy group.

According to the UN Environment Programme, developing countries accounted for about 60 percent of global greenhouse gas emissions in 2010.

"Today developing and developed countries are responsible for roughly equal shares of cumulative greenhouse gas emissions for the period 1850-2010," said its latest Emissions Gap Report.

Scientists say at least 60 percent of known fossil fuels must stay in the ground if warming is to be sufficiently curtailed.

"It is a matter of brutal arithmetic that even if all of the rich countries cut their emissions to zero, the current growth in annual emissions by poor countries would still mean a high probability of global warming exceeding" the 2 C target, economic policy expert Bob Ward of the London School of Economics told AFP.

Greenpeace executive director Kumi Naidoo accused governments on both sides of blocking progress "while serving their coal and oil lobbies rather than their people".

Chinese climate envoy Xie Zhenhua told delegates this week that developed nations' "historical responsibility" for climate change could not be denied.

"And there is no ignoring the priority needs of developing countries for sustained development and poverty elimination", which requires energy.

"To balance the interests of developed countries and developing ones is delicate indeed," said Hans Schellnhuber, director of the Potsdam Institute for Climate Impact Research in Germany.

"It is clear that the industrialised countries have a historic responsibility, but this doesn't free the rest of the world from the responsibility to act, too."

With the world's poorest countries and small island states increasingly on edge, they also don't want to risk losing negotiating clout through a standoff with loud-voiced developing nations.

"It is not in our interests to dissociate ourselves from China. The only time that developing countries have managed to obtain anything serious, is when they are united," African Group spokesman Seyni Nafo told AFP on the margins of the talks.

For Naidoo, the tone of the debate must shift if the planet is to be safeguarded for future generations.

"Now is the time for us to get it right as rich and poor countries united," he said.

"If we get it wrong, true poor countries will pay the first and most brutal price, but ultimately no country will be immune from climate impacts."