A coalition of countries and agencies seeking to curb Earth-warming pollutants like soot released by wood-fired ovens and methane from oil extraction, on Tuesday welcomed seven new members to its fold.

At a meeting in Paris, the Clean Air and Climate Coalition launched by US Secretary of State Hillary Clinton in February, said Britain, Denmark, Finland, France, Germany, Italy and Jordan were its latest members.

They joined the United States, Bangladesh, Canada, Colombia, the European Commission, Ghana, Japan, Mexico, Nigeria, Norway, Sweden, the World Bank, the UN Environment Programme (UNEP) and the Stockholm Environment Institute -- bringing to 21 the number of members of the voluntary coalition.

"The idea is to come together around a network to scale up actions that could reduce these short-lived pollutants in the near term," United States deputy special envoy for climate change Jonathan Pershing told journalists.

"If we are able to do this we can really buy time in the context of the global problem to combat climate change -- time that we need desperately as the rate of emissions continue to rise globally."

Short-lived pollutants like black carbon or soot, methane and fluorinated gases called HFCs can potentially be eliminated from the atmosphere in a much shorter period of time than CO2, which is the main target of international efforts to curb global warming but also the cause of much political bickering.

Potentially deadly soot is emitted from brick-baking kilns and wood-fired stoves used in developed countries, diesel engines in trucks, cars and electricity generators, and the burning of organic waste.

It causes respiratory diseases in people and smothers crops, and settles in the Arctic where it absorbs the sun's heat, warms up the atmosphere and contributes to glacier melt.

"It is a matter of public health. Over two million people in the world, perhaps even four million according to the latest estimates from scientists, are dying every year from outdoor air pollution," said UNEP chief scientists Joseph Alcamo.

Another two million die annually from indoor pollution from cooking stoves.

Methane is considered a greenhouse gas 20 times more potent than carbon dioxide, and is emitted by landfill decomposition as well as oil and gas extraction and some farming practices.

Climate-warming HFCs are commonly used in refrigerators and air conditioners.

"Fast action to reduce these pollutants, especially methane and black carbon, has the potential to slow down the warming expected by 2050 by as much as 0.5 degrees Celsius," said a coalition document.

The UN has set a 2 C (3.6 degree Fahrenheit) limit on warming from pre-industrial levels for manageable climate change.