More than 100 groups have issued a letter supporting a legal petition filed by the Center for Biological Diversity and 350.org that would requires the US Environmental Protection Agency to establish national safe limits for carbon dioxide and other greenhouse gas pollution under the Clean Air Act.

The petition seeks to have greenhouse gases designated as 'criteria' air pollutants and atmospheric carbon dioxide capped at 350 parts per million (ppm), the level leading scientists say is necessary to avoid the worst impacts of climate change.
 
Individuals supporting the petition include climate scientist, James Hansen, and Sierra Club board member, Michael Dorsey.
 
Dorsey said: 'The Center for Biological Diversity and 350.org's petition is a bold step that can further enable President Obama to move in the right direction to quickly rein in climate change. Organisations and commentators that suggest the contrary misunderstand the urgency of avoiding a catastrophically destabilised climate.'
 
The Obama administration has proposed emissions reduction targets of just three per cent below 1990 levels by 2020, far below the cuts of approximately 45 per cent necessary to get back to 350 ppm.
 
The administration has argued that its hands are tied by the weak cap-and-trade bills passed by the House of Representatives and under consideration by the Senate. In a report released in Copenhagen, titled Yes, He Can: President Obama's Power to Make an International Climate Commitment Without Waiting for Congress, the Center concludes that the president need not wait for Congress to act before taking strong action to reduce US emissions.

Hansen said: 'Setting science-based, national pollution caps for greenhouse gases - such as no more than 350 ppm for carbon dioxide - would mark a critical step in the fight against global warming, and this petition is one way to bring us closer to that goal.'