World leaders gathered in Paris Monday to kick off two weeks of talks aimed at crafting an agreement that could put the brakes on heat-trapping greenhouse gas emissions blamed by many scientists for warming the planet to record levels.

Led by President Obama, leader after leader laid out what they would do to address the issue of climate change. They also praised France for holding the talks just two weeks a devastating terror attack by militants linked to the Islamic State group killed 130 people around the city.

“Nearly 200 nations have assembled here this week -- a declaration that for all the challenges we face, the growing threat of climate change could define the contours of this century more dramatically than any other,” Obama told delegates from 180 nations. “What should give us hope that this is a turning point, that this is the moment we finally determined we would save our planet, is the fact that our nations share a sense of urgency about this challenge and a growing realization that it is within our power to do something about it.”

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Ahead of the talks, U.N. climate chief Christiana Figueres told Fox News that she expects to see a global agreement that will keep temperatures from rising 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels and will include details on how countries will reduce their emissions beyond the next 15 years. It will also spell out “how that is going to be monitored verified, reviewed, how the accountability is going to be done," she said.

There will also be a push to ensure that rich nations make good on a promise in 2009 to provide poor nations with $100 billion a year to help develop greener economies and adapt to impacts of climate change in the coming decades that will include widespread droughts, rising seas and worsening storms.

The talks, however, have raised the ire of some Republicans back in the United States.

Led by skeptics like Sen. Jim Inhofe, R-Okla., chairman of the Senate Environment and Public Works Committee, they have threatened to withhold funding for his climate plans unless Obama seeks congressional approval for any deal.

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Many have downplayed the impact of climate change and fear that an international agreement will end up hurting the American economy. They also question whether any deal would make a difference, fearing American and European cuts would be more than offset by the continued growing emissions from China and India.

At this point, the U.N. estimates that a deal would cover at least 86 percent of greenhouse gas emissions worldwide and reduce the threat of runaway temperatures in the decades ahead – but it would not prevent rising above the 3.6 degree Fahrenheit threshold, the point where scientists fear the worst impacts of climate change would take hold.

“We are no longer heading to a world that would increase temperatures by 4, 5 or sometimes even 6 degrees (Celsius) according to some studies, which is what we had a few years ago. But, rather, with full implementation of these climate change plans, we could be heading to a future that would increase the global temperature by 2.7 or 3 degrees,” Figueres told Fox News.

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“Is it enough? No. It clearly is not enough. So it’s a very good start, a movement in the right direction, but it’s very clear that these national climate change plans are a down payment, if you will, on the transformation that needs to increase in scale and in pace.”

Even so, any deal would be an improvement over past talks that have repeatedly faltered over whom is the blame for rising emissions and the refusal of developing nations to commit to emissions cuts – a key fault of 1997 Kyoto Protocol.

 This time, the United States and China set the tone early on by committing to reaching a deal in Paris and also laying out what actions each nation would take. The U.S. says it will reduce emissions 26-28 percent below 2005 levels by 2025. China has agreed to cap emissions by 2030, or earlier if possible, and increase the share of energy it derives from sources other than fossil fuels.

India, another big emitter, has promised to reduce its emissions intensity by 33-35 percent below 2005 levels by 2030 and to increase electricity generated by sources other than fossil fuels by 40 percent.

Critics have called on India to go further and pledge to cut their emissions – something it has resisted, claiming rich nations bear most of the responsibility for climate change. Obama, after meeting Indian Prime Minister Narendra Modi on Monday, that a deal in Paris "must recognize and protect the abilities of countries like India to pursue the priorities of development, growth, and poverty eradication" while ensuring that it reflects "serious and ambitious action by all nations to curb their carbon pollution."

Another factor raising the prospect of a deal is the growing affordability of renewables especially solar and wind energy – making it easier for countries to shift away from fossil fuels like coal and oil and holding out hope that developing nations won’t have to slow their economies in order to go green.

That was highlighted Monday, when Bill Gates announced that he and other investors are pledging $7 billion for research and development of clean energy, according to The Associated Press. The Microsoft co-founder is announcing the investment as part of a larger initiative with world governments that are promising to double spending on renewable energy research.

The Associated Press contributed to this report.