Attention Sunday turned to enforcement of the landmark environmental agreement approved by nearly 200 of the world's nation this weekend in France. U.S. Secretary of State John Kerry said he was hopeful for the pact's implementation but acknowledged there was no mechanism to make sure nations meet the ambitious accord's goals.

The deal, which culminated two weeks of negotiations, aims to limit global warming by setting a temperature cap of 2 degrees Celsius change, with an aim for 1.5 degrees change, which is to be met through a worldwide shift away from fossil fuels and toward more renewable sources of energy. The long-term goal is to move away almost entirely from fossil fuels in the next 50 years. Each of the 195 countries that signed the agreement will need to have it approved by their respective governments for the terms to be made law.

Kerry called the pact a "breakaway agreement" that will reshape the discussion surrounding climate change. "The business community of the entire world is receiving a message of countries now moving toward clean, alternative, renewable energy and trying to reduce their carbon footprint," Kerry said during an interview on CBS's "Face the Nation" Sunday, adding, "That is going to spur massive investment."

Activists and representatives from governments alike have been critical over how the agreement will be enforced. Kerry and others noted that the agreement is essentially a set of at-will promises made by each country with no singular authority responsible for holding them accountable or making sure they are fulfilled.

The last climate summit took place in Copenhagen, Denmark, in 2009 and did not result in any lasting agreement. Talks broke down toward the end of the summit and few long-term changes were implemented in the participating countries. Critics of the Paris summit were skeptical in particular the U.S. would follow through on its promises to cut emissions, especially if a climate change doubter is elected president in 2016.

All of the Republican candidates in the race have said they do not approve of cutting carbon emissions, and representatives from other countries said they fear the U.S. political atmosphere could jeopardize the success of the deal. “You cannot bank on the Americans to follow through,” Nozipho Mxakato-Diseko, a South African diplomat and a negotiator at the climate talks, told the Wall Street Journal Sunday.

Other experts in the field were cautiously hopeful, noting though the pact was at-will, the desire for change during the Paris summit was greater than at any prior talks. "These climate talks differed substantially from the prior ones because they gave audience to resilience,” said Joyce Coffee, managing director of the global adaptation index ND-GAIN in a statement. 

“Not only was the first-ever resilience day held as an official part of the two-week conference, but the final agreement includes the word adaptation more frequently than the word mitigation,” Coffee said.