World leaders who gathered in Paris this week to negotiate a climate deal described it as one of the most important meetings in human history - a prerequisite to staving off a catastrophic rise in global temperatures.
Then there are the Republican candidates looking to succeed President Obama, who have greeted the COP21 event with a mix of yawns and jeers. In Washington, GOP congressional leaders are working to derail the Paris plan to curb emissions and are even warning foreign leaders not to trust Obama's promises.
Scientists, politicians and citizens around the world are coalescing in favor of international action. While the exact consequences of failure are unknown, the overwhelming consensus among scientific researchers is that the carbon emissions warming the planet could cause an array of effects from droughts to rising sea levels if left unchecked.
"Never have the stakes been so high because this is about the future of the planet, the future of life," French President Francois Hollande said on the conference's opening day.
The Republican Party, meanwhile, has largely moved in the opposite direction. After a brief GOP flirtation with environmentalism in the 2000s, the entire top tier of the 2016 presidential field is skeptical of efforts to address carbon emissions or outright hostile to the science driving the issue. This includes candidates with relatively mainstream credentials like former Florida Gov. Jeb Bush, Ohio Gov. John Kasich, and Florida Sen. Marco Rubio as well as more untraditional contenders like Donald Trump, Texas Sen. Ted Cruz and Dr. Ben Carson.
Bush, who has questioned the extent to which human behavior causes climate change, repeatedly lambasted the Paris talks this week on the campaign trail.
"I'm not sure I would have gone to the climate summit if I was president today," he told reporters on Tuesday, citing potential economic dangers to restricting carbon emissions.
At an Iowa town hall, Bush said he feared threats to the nation's "sovereignty" from a climate deal, while cautioning he still had not seen the final product of the conference. The Bush campaign emailed the press a radio appearance in which he criticized Obama for, in the candidate's view, putting climate ahead of the economy and terrorism.
Rubio, who has long questioned climate science, has performed a similar dance. On Fox News Monday, Rubio argued there's no scientific "consensus" on the issue. At the same time, he said that even if the science is correct, it's futile for the U.S. to cap emissions given that it would take a global effort with countries like China to make a serious impact. "America is not a planet," he said at a GOP primary debate in September.
That sounds an awful lot like an argument in favor of the Paris talks, but Rubio's not a fan of them either and has told supporters they will have "no meaningful effect on climate change."
Kasich has said he "[doesn't] believe that humans are the primary cause of climate change." New Jersey Gov. Chris Christie said on MSNBC's "Morning Joe" Tuesday that climate change "is not a crisis" based on his gut instinct.
Among other GOP candidates, opposition is even stronger. Trump has claimed that climate science is a hoax and said on Tuesday it was "ridiculous" for Obama to worry about the issue. Cruz has mocked climate science as a "religion" and said in Iowa Tuesday that Obama "apparently thinks having an SUV in your driveway is more dangerous than a bunch of terrorists trying to blow up the world."
The three Democratic presidential hopefuls, Hillary Clinton, Bernie Sanders and Martin O'Malley, are lined up behind Obama's efforts to tackle climate change and have pledged to continue efforts to lower emissions if elected. The stark contrast makes climate one of many issues where the presidential election could have a lasting impact on policy for years to come.
How much of an impact is not entirely clear. For now, Obama can veto challenges from congressional Republicans to his proposals. Even if a Republican is elected to succeed Obama and has control of Congress and more power to shift policy gears, he or she might be constrained by existing regulations, court cases, and international commitments from going too far.