Diplomats will descend on Paris at the end of November for United Nations climate talks that could prove pivotal in the fight against global warming. President Obama has labored to show that the U.S. is serious about taking action to stave off the worst impacts of rising temperatures. But Republican critics, led by Senate Majority Leader Mitch McConnell, are warning the world that the president’s environmental promises are built on shaky ground—and could easily crumble.

Republican opponents lack the votes to block the central pillars of the president’s climate agenda. Still, the clash over the Paris talks stands as a sharp reminder that congressional opposition forced the White House to abandon ambitions for comprehensive climate legislation. Policy experts warn that governments must do everything in their power to reckon with the reality of global warming as an environmental, economic, humanitarian, and national security threat. Instead, the president has been compelled to advance a climate agenda in bits and pieces.

The dispute in Congress highlights how polarized the U.S. climate debate has become. Democrats and Republicans struggle to agree on the nature of the threat, much less what should be done to confront it. Despite the fact that the U.S. military considers climate change a “threat multiplier,” both conservative commentators and Republican White House contenders like Rand Paul and Mike Huckabee decry the idea that climate change should be viewed as a major threat to national security. Some House Republicans have publicly expressed concern over the security risks of a warming planet, but that falls far short of a bipartisan consensus. Meanwhile, experts warn that it would be shortsighted to allow partisan disputes to create a blind spot in American foreign policy.

“We can’t pick and choose whether we deal with climate change or ISIS or Russia, we have to deal with all of those problems,” Francesco Femia, the director of the Center for Climate and Security think tank said in an interview. “With the U.S. as the so-called guarantor of international security, we need to walk and chew gum at the same time.”

Of course, Obama isn’t waiting for Congress’ stamp of approval. The Environmental Protection Agency has taken action to impose regulations aimed at curbing greenhouse gases from power plants. Other federal agencies are limiting their carbon footprints and factoring climate impacts into policy decisions. But since many of these directives have come from the president and not Congress, they are more susceptible to being reversed by the next administration.

It’s not just national security that stands to be impacted by a warming planet. Scientists predict that climate change will cause the frequency and intensity of extreme weather events to increase, and vulnerable populations are expected to be hard hit. Democratic presidential contenders Hillary Clinton and Martin O’Malley have linked climate change to humanitarian disasters such as the Syrian refugee crisis. But that is hardly a common refrain on the campaign trail. Yet migration experts warn that governments should take climate and disaster forecasting into account when developing humanitarian and migration assistance policy.

“We need to connect people working on disaster risk reduction with people working on climate change adaptation with people working on migration and refugees. There needs to be an integrated thinking about how we will deal with climate change across many different policy areas,” said Jane McAdam, the director of the Andrew and Renata Kaldor Centre for International Refugee Law at the University of New South Wales.

“There are always a number of factors that lead to displacement—so you can’t say it’s climate change full stop. But it will be climate change, overlaid on existing pressures like overpopulation and lack of income earning opportunities. So it can become the straw that broke the camel’s back,” McAdam added.

Climate change may also have major economic impacts. The economy is already front-and-center in the climate debate, but Republicans and Democrats in Congress consistently talk past one another when it comes to discussing economic risks. Republicans often focus the political conversation on the cost of environmental regulation. McConnell, for example, warns that the president’s power-plant regulations will kill jobs and stamp out the coal industry. Democrats, on the other hand, tend to emphasize the cost of inaction.

“It’s not a very well informed debate,” said Robert Engle, a professor of finance at New York University’s Stern School of Business and a Nobel Laureate in economics. “Ultimately there are going to be enormous costs involved. The costs to business and society I think are likely to be enormous. Even so far as saying that life as we know it can’t survive, that’s the ultimate risk.”

As the president races to shore up his environment legacy, Republican opponents are working to thwart the administration. Conservative critics are threatening to withhold funding that the administration has pledged to set aside to cut carbon pollution and strengthen the resilience of developing countries to climate change. Republicans say that unless the administration allows the Senate to review any international climate deal negotiated in Paris, Congress won’t authorize the funds. The administration has expressed confidence that it will find a way to turn its promise into reality. Yet the dispute stands as another example of how congressional opposition creates challenges for the White House as it seeks to implement its green agenda.   

As evidence mounts that rising temperatures will have widely felt consequences, climate policy that does not take a comprehensive approach may prove inadequate. A debate that obscures the ways that climate change interacts with and exacerbates other threats could also leave the country profoundly unprepared.

“The conversation has to get broader,” Femia said. “We have to talk about what climate change means not only for our military, but for our health institutions, we have to ask the question of are we prepared for what climate change might mean for the spread of disease, what it will do to our agricultural base and how it will impact our friends and allies.”