Scientists asked people around the world on Monday to help compile an Internet-based observatory of life on earth as a guide to everything from the impact of climate change on wildlife to pests that can damage crops.

Rich nations as a group are unlikely to reach the deep 2020 cuts in greenhouse gas emissions urged by developing nations as part of a new UN climate treaty, the top US climate envoy said on Friday.

Washington defended its plans to cut its greenhouse gas emissions as among the most ambitious in the world Tuesday as major economies meeting in Paris rallied around a Mexican plan to raise cash to fight climate change.

China won praise for moves to cap its surging greenhouse gas emissions at a meeting of major economies on Tuesday, even as Germany criticised the lack of progress towards a new United Nations climate treaty.

"China is very active," French Environment Minister Jean-Louis Borloo told reporters on the second day of the two-day meeting of 17 major emitters.

France and Germany suggested on Monday that rich nations should collectively guarantee deep cuts in greenhouse gases by 2020 while giving flexibility to laggards such as the United States to catch up later.

Tens of billions of dollars are likely to be needed to help poor nations curb greenhouse gas emissions and adapt to climate change under a new U.N. treaty, European Environment Commissioner Stavros Dimas said.

Solar power plants in deserts using mirrors to concentrate the sun's rays have the potential to generate up to a quarter of the world's electricity by 2050, a report by pro-solar groups said on Monday.

A rise in concentrations of a powerful greenhouse gas over the Arctic after a decade of stability is stirring worries about a possible thaw of vast stores trapped in permafrost, experts said.

Many governments are ignoring alien invasive species such as weeds or rats that may be causing $1.4 trillion damage a year to the world economy, the head of the U.N. Environment Program (UNEP) said on Friday.

The United Nations issued a range of rival ideas for fighting climate change from rich and poor nations on Wednesday and said the world was "not standing still" in work on a new U.N. treaty.