*Editor's note: This story has been updated throughout. 

Negotiators from nearly 200 nations, including the United States, inked an unprecedented climate agreement on Saturday that calls for every country to cut greenhouse gas emissions to help combat the most harmful effects of global warming.

The accord was reached at the tail end of a two-week U.N. conference in Paris where delegates from 195 countries, large and small, worked feverishly to strike a deal that had been elusive in the past. And it could have big implications for Texas, the nation's biggest carbon emitter.

“In my first inaugural address, I committed this country to the tireless task of combating climate change and protecting this planet for future generations,” President Obama said Saturday during a White House news conference. “Two weeks ago in Paris I said before the world that we needed a strong global agreement to accomplish this goal — an enduring agreement that reduces global carbon pollution and sets the world on a course to a low carbon future. A few hours ago, we succeeded. We came together around a strong agreement the world needed.”

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The accord is not perfect and will not solve the issue, Obama said, noting that “even if all the initial targets are met we’ll only be part of the way there when it comes to reducing carbon from the atmosphere.”

Still, the Paris agreement ambitiously seeks to keep the increase in global average temperatures from rising 2 degrees Celsius, or 3.6 degrees Fahrenheit, above pre-industrial levels and says efforts should be made to limit warming to 1.5 degrees Celsius. Scientists believe 2 degrees Celsius of warming is a point-of-no-return maximum when the Earth will experience the worst consequences of global warming, including sea level rise, more intense storms and more severe droughts. 

Some, including the "father of climate change awareness," have cast doubt on the strength of the Paris agreement, under which countries will voluntarily create their own plans to reduce emissions of planet-warming greenhouse gases. Under the accord, they will disclose and update those plans every five years starting in 2018.

A recent analysis of plans submitted by countries ahead of the Paris talks showed they still would allow the globe to warm by more than 6 degrees Fahrenheit. But the same researchers who conducted that analysis said Monday that the agreement's 2-degree goal could be met if nations submit stricter initial plans and implement more ambitious ones every five years.

The United States' plan says it will reduce greenhouse gas emissions by 26 to 28 percent from 2005 levels by 2020 and try its hardest to achieve the higher percentage reduction. Whether the country will actually carry that out depends on who is elected president in 2016, with every Republican contender having cast doubt on established climate science. 

Any additional federal policies that result from the Paris agreement are likely to have big implications for Texas — the nation’s No. 1 greenhouse gas emitter and energy producer — and also to face big pushback from the state's Republican leaders, who routinely question, or deny, the scientific consensus that human activity is the main driver of climate change. 

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Attorney General Ken Paxton, along with about two dozen other states, already is suing over Obama’s main plan to combat global warming, which was finalized this year. The Clean Power Plan requires states to cut carbon emissions by shifting from coal power to natural gas and renewables over the next 15 years.

Leading up to the Paris talks, Paxton cast doubt on the federal government's ability to enforce any climate accord.

“There are significant legal limits on [President Obama’s] ability either to carry out the promises he has made in advance of Paris 2015 or to enforce any agreement arising out of the summit,” Paxton wrote in a letter to Obama with West Virginia Attorney General Patrick Morrisey, who also is suing over the Clean Power Plan.

“These serious legal questions are of great importance to the States,” the attorneys general wrote. “We expect our federal representatives to respect that system of dual sovereignty both here at home and in negotiations abroad.”

U.S. Sen. John Cornyn echoed the same sentiment on Twitter.

"Strange reading press on Paris climate 'agreement': under Constitution POTUS (Obama) has no unilateral authority to bind US; so it is his, not ours," the Texas Republican said on Sunday.

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