Los Angeles, California:
US President Barack Obama's decision to attend the Copenhagen Climate Summit this week offered high-level backing to the talks and sent a message to the world that climate change was back on Washington's list of priorities.
The US chief executive's decision also indicated the Americans see a chance for important political agreements in the final hours of the summit, when United Nations talks perennially go into overtime in last-minute wrangling and when other leaders are planning to take part.
Obama put global warming and climate change back on the US agenda, after eight years of seeming inertia during the administration of former President George W Bush.
But now as leaders from around the world gather in the Danish capital to draft an agreement to replace the Kyoto Protocol, which expires in 2012, the world is looking to see what Washington will do next.
In a signal the Obama administration may be prepared to act without US congressional action, the US Environmental Protection Agency (EPA) said it has concluded that greenhouse gases are endangering Americans' health and must be regulated.
The EPA said the scientific evidence surrounding climate change clearly shows that greenhouse gases "threaten the public health and welfare of the American people" and that the pollutants - mainly carbon dioxide from burning fossil fuels - should be regulated under the Clean Air Act.
Climate activists in Copenhagen said the decision could help the Obama administration move ahead on climate policy without waiting for action from Congress.
However, a White House spokesman said on Monday that Obama still prefers legislation on climate change and that Monday's US Environment Protection Agency declaration was a response to a court-ordered timetable.
But the US, which shunned the Kyoto Protocol during Bush's eight years in office, is still seen as the linchpin to a deal.
Obama has stressed that he is heading to Copenhagen looking for a comprehensive framework agreement rather than a legally binding document to reduce global carbon emissions.
The White House has said that Obama would offer to reduce US carbon dioxide and other global-warming emissions by about 17 percent below 2005 levels by 2020. However, the pledge would be provisional depending on the level set by legislation slowly making its way through the US Congress.
Obama's administration gained some momentum in June when the House of Representatives passed a climate bill.
The legislation would require the US to reduce carbon dioxide and other greenhouse emissions by 17 per cent from 2005 levels by 2020 and by about 80 per cent by mid-century.
However, many still accuse the US of dragging its feet when it comes to climate change.
Not so, says Yvo de Boer, Executive Secretary of the United Nations Framework Convention on Climate Change. "I actually don't see the United States dragging its feet," de Boer said.
"I see President Obama having committed to show leadership on this topic, stating his intent to come to Copenhagen. Secondly, I know that the US House of Representatives has already finalised climate legislation and this legislation is now being considered by the Senate, so I think that both the administration and the people's representation are working really hard to come to Copenhagen with something strong."
However, the bill would still have to pass through the Senate.
"If the Senate produces a comprehensive draft that reflects consensus support...I think that's the threshold that will enable the United States to play the leadership role the rest of the world expects of us," said Al Gore, environmental advocate and former US vice-president.
Many feel that the divisions over legislation reflect the US public's confusion over what needs to be done to combat climate change and cut emissions.
Eileen Claussen, president of the centrist Pew Centre for Global Climate Change says the often mentioned point that people would need to give up their cars to cut emissions is not a "a necessary part of the solution."
Nonetheless, some residents of Los Angeles - one of the more polluted cities in the US - said they would be willing to give up their cars to fight climate change.
While others said the city would need to improve public transportation before they consider any drastic changes.
But Claussen says climate change is likely to remain on the backburner in the US as it continues to be overshadowed by more pressing issues such as the economy, unemployment and the ongoing health care debate.
Several officials in President Obama's administration have sought to reign in the expectations surrounding Copenhagen.
US Secretary of State Hillary Clinton said recently during a trip to the Philippines, that the summit is not likely to produce a legally binding treaty.
Clinton said the legally binding agreement would not happen "because too many countries have too many questions."
But Damon Moglen, the Director of Greenpeace's Warming Campaign disagrees. Moglen believes the United States is "the number one problem for Copenhagen."
He said the US needs to show to the developed world that it will bring down its emissions levels and bring "money to the table which is going to help the developing world respond to climate change, which is already destroying their lives in many ways."
Analysts on the other side of the spectrum argue that a comprehensive US climate bill and agreement at Copenhagen could actually weaken the already vulnerable US economy.
They argue that environmental restrictions would result in slower domestic economic growth and possible job losses.
With the US facing so many domestic and international challenges ahead of Copenhagen, the chances of a legally binding document seem slim.
But slow progress has marked climate talks since the 1992 Rio treaty calling for voluntary controls on greenhouse gases.
It took five more years to get the Kyoto Protocol, which ordered emissions cuts by 37 industrialised nations, an accord the US rejected.
US resistance through eight years under Bush then blocked most progress. But while diplomacy has inched along, climate change hasn't waited.
Global temperatures are rising by 0.19 degrees Celsius (0.34 degrees Fahrenheit) per decade and twice as fast in the far north, melting Arctic sea ice at record rates.
In the Copenhagen talks' final days, the World Meteorological Organisation is expected to confirm this was the warmest decade on record.
Oceans, expanding from warmth and melting glaciers, are rising faster than predicted.
The world's power plants, automobiles, burning forests and other sources are producing 29 percent more carbon dioxide than in 2000.
That emissions path could drive temperatures by 2060 to at least 4 degrees C (7 degrees F) higher than pre-industrial levels, scientists say.
That would push the world deeper into a time of climate disruption, unusual droughts and powerful storms, species die-offs, spreading tropical diseases, coastal flooding and other, unpredictable consequences.
The US chief executive's decision also indicated the Americans see a chance for important political agreements in the final hours of the summit, when United Nations talks perennially go into overtime in last-minute wrangling and when other leaders are planning to take part.
Obama put global warming and climate change back on the US agenda, after eight years of seeming inertia during the administration of former President George W Bush.
But now as leaders from around the world gather in the Danish capital to draft an agreement to replace the Kyoto Protocol, which expires in 2012, the world is looking to see what Washington will do next.
In a signal the Obama administration may be prepared to act without US congressional action, the US Environmental Protection Agency (EPA) said it has concluded that greenhouse gases are endangering Americans' health and must be regulated.
The EPA said the scientific evidence surrounding climate change clearly shows that greenhouse gases "threaten the public health and welfare of the American people" and that the pollutants - mainly carbon dioxide from burning fossil fuels - should be regulated under the Clean Air Act.
Climate activists in Copenhagen said the decision could help the Obama administration move ahead on climate policy without waiting for action from Congress.
However, a White House spokesman said on Monday that Obama still prefers legislation on climate change and that Monday's US Environment Protection Agency declaration was a response to a court-ordered timetable.
But the US, which shunned the Kyoto Protocol during Bush's eight years in office, is still seen as the linchpin to a deal.
Obama has stressed that he is heading to Copenhagen looking for a comprehensive framework agreement rather than a legally binding document to reduce global carbon emissions.
The White House has said that Obama would offer to reduce US carbon dioxide and other global-warming emissions by about 17 percent below 2005 levels by 2020. However, the pledge would be provisional depending on the level set by legislation slowly making its way through the US Congress.
Obama's administration gained some momentum in June when the House of Representatives passed a climate bill.
The legislation would require the US to reduce carbon dioxide and other greenhouse emissions by 17 per cent from 2005 levels by 2020 and by about 80 per cent by mid-century.
However, many still accuse the US of dragging its feet when it comes to climate change.
Not so, says Yvo de Boer, Executive Secretary of the United Nations Framework Convention on Climate Change. "I actually don't see the United States dragging its feet," de Boer said.
"I see President Obama having committed to show leadership on this topic, stating his intent to come to Copenhagen. Secondly, I know that the US House of Representatives has already finalised climate legislation and this legislation is now being considered by the Senate, so I think that both the administration and the people's representation are working really hard to come to Copenhagen with something strong."
However, the bill would still have to pass through the Senate.
"If the Senate produces a comprehensive draft that reflects consensus support...I think that's the threshold that will enable the United States to play the leadership role the rest of the world expects of us," said Al Gore, environmental advocate and former US vice-president.
Many feel that the divisions over legislation reflect the US public's confusion over what needs to be done to combat climate change and cut emissions.
Eileen Claussen, president of the centrist Pew Centre for Global Climate Change says the often mentioned point that people would need to give up their cars to cut emissions is not a "a necessary part of the solution."
Nonetheless, some residents of Los Angeles - one of the more polluted cities in the US - said they would be willing to give up their cars to fight climate change.
While others said the city would need to improve public transportation before they consider any drastic changes.
But Claussen says climate change is likely to remain on the backburner in the US as it continues to be overshadowed by more pressing issues such as the economy, unemployment and the ongoing health care debate.
Several officials in President Obama's administration have sought to reign in the expectations surrounding Copenhagen.
US Secretary of State Hillary Clinton said recently during a trip to the Philippines, that the summit is not likely to produce a legally binding treaty.
Clinton said the legally binding agreement would not happen "because too many countries have too many questions."
But Damon Moglen, the Director of Greenpeace's Warming Campaign disagrees. Moglen believes the United States is "the number one problem for Copenhagen."
He said the US needs to show to the developed world that it will bring down its emissions levels and bring "money to the table which is going to help the developing world respond to climate change, which is already destroying their lives in many ways."
Analysts on the other side of the spectrum argue that a comprehensive US climate bill and agreement at Copenhagen could actually weaken the already vulnerable US economy.
They argue that environmental restrictions would result in slower domestic economic growth and possible job losses.
With the US facing so many domestic and international challenges ahead of Copenhagen, the chances of a legally binding document seem slim.
But slow progress has marked climate talks since the 1992 Rio treaty calling for voluntary controls on greenhouse gases.
It took five more years to get the Kyoto Protocol, which ordered emissions cuts by 37 industrialised nations, an accord the US rejected.
US resistance through eight years under Bush then blocked most progress. But while diplomacy has inched along, climate change hasn't waited.
Global temperatures are rising by 0.19 degrees Celsius (0.34 degrees Fahrenheit) per decade and twice as fast in the far north, melting Arctic sea ice at record rates.
In the Copenhagen talks' final days, the World Meteorological Organisation is expected to confirm this was the warmest decade on record.
Oceans, expanding from warmth and melting glaciers, are rising faster than predicted.
The world's power plants, automobiles, burning forests and other sources are producing 29 percent more carbon dioxide than in 2000.
That emissions path could drive temperatures by 2060 to at least 4 degrees C (7 degrees F) higher than pre-industrial levels, scientists say.
That would push the world deeper into a time of climate disruption, unusual droughts and powerful storms, species die-offs, spreading tropical diseases, coastal flooding and other, unpredictable consequences.
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