This year has been the warmest ever since mankind started keeping record 135 years ago, and with so much evidence now in the books that man-made global warming is happening, the big questions in scientists’ minds is: What will governments do about it in 2015?

Next year will culminate with an important climate summit in Paris next December, but there will be many important milestones to be hit leading up to that, particularly when it comes to the world’s two biggest polluters, the United States and China, according to NBC News.

In an important step, they both acknowledged their role in the situation and pledge to cut back on emissions. Nations around the world will be watching to see if they make big steps to shoulder the burden or merely assign blame.

Chris Field, director of the Carnegie Institution’s Department of Global Ecology at Stanford University, said in the NBC News report that key to success in 2015 will be solutions. Since they are meeting in Paris to forge an international agreement, it will “be a big year for local, state, national, and international discussions.”

There is some momentum heading into this year, particularly the agreement between the U.S> and and China to pledge significant reductions in carbon emissions — President Obama proposing to reduce emissions by a quarter by 2025, and China President Xi Jinping pledging to halt growth of CO2 emissions by 2030.

Further, international talks were held in Peru earlier this month that could serve as a warm-up to the Paris meeting that could help nations to focus on what it will take to actually curb global emissions.

However, the U.S.-China agreement is where real change on climate change is likely to begin, and there is still a ways to go.

The biggest problem with the accord is its non-binding nature. This has given Republicans the opportunity to criticize the accord, arguing that the U.S. will have to make sacrifices but China can ignore its responsibility if it wants. Republicans have indicated they don’t want to make sacrifices if China isn’t willing to do so as well. Senate Majority Leader Mitch McConnell (R-Ky.) complained that the Chinese won’t have to do anything for 16 years under the agreement while “these carbon emission regulations are creating havoc in my state and other states across the country.”

This sort of mistrust due to the non-binding nature of the agreement risks halting the momentum seen in 2014, especially now that Congress will take control of Congress in 2015.

However, there are signs of hope elsewhere. Large developing countries other than China and the U.S. are starting to get involved, according to Field, which he called “critically important.”

If world leaders aren’t able to get the ball rolling, the effects of climate change may force their hand eventually. Heat is already becoming a noticeable factor int he world, with 2014 overtaking 2010 as the warmest on record, posting a temperature that was 1.22 degrees higher than the 20th Century average of 57 degrees Fahrenheit.