The first tensions at the UN climate talks have emerged as island and African nations criticised rich countries for refusing to offer new emissions cuts.

The debate swung around the Kyoto Protocol - a legally-binding emissions cap that expires this year and remains the most significant international achievement in the fight against global warming. Countries are hoping to negotiate an extension to the pact that runs until at least 2020 but several nations like Japan and Canada have said they will not be party to a new one.

Marlene Moses, chairwoman of a coalition of island countries, said she was "gravely disappointed" with rich nations, saying they have failed to act or offer up any new emissions cuts for the near term. The United States, for example, which is not a signatory of Kyoto, has said it would not increase earlier commitments to cut emissions by 17% below 2005 levels by 2020.

"In our view, these actions are an abdication of responsibility to the most vulnerable among us," Ms Moses said.

In its current form, a pact that once incorporated all industrialised countries except the United States would now only include the European Union, Australia and several smaller countries which together account for less than 15% of global emissions.

The Japanese delegation defended its decision not to sign onto an extension, insisting it would be better to focus on coming to an agreement by 2015 that would require all countries to do their part to keep global temperatures from rising more than 2C.

The position of Japan and other developed countries has the potential to reignite the battles between rich and poor nations that have doomed past efforts to reach a deal.

Some scientists say extreme weather, such as Hurricane Sandy's onslaught on the US, will become more frequent as the Earth warms, although it is impossible to attribute any individual event to climate change.

Meanwhile, a United Nations report warned that thawing permafrost covering almost a quarter of the northern hemisphere could "significantly amplify global warming" at a time when the world is already struggling to reign in rising greenhouse gases.

The UN said the potential hazards of carbon dioxide and methane emissions from warming permafrost has until now not been factored into climate models. It is calling for a special UN climate panel to assess the warming and for the creation of "national monitoring networks and adaptation plans" to help better understand the threat.

In the past, land with permafrost experienced thawing on the surface during summer but now scientists are witnessing thaws up to 10 feet deep due to warmer temperatures. The softened earth releases gases from decaying plants that have been stuck below frozen ground for millennia.

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