Secretary of State John Kerry said Tuesday that the climate deal reached in Paris this month is the most important thing State worked on all year, more important than even the agreement to curb Iran's nuclear program.

"As one year gives way to the next, international leaders have an opportunity to build on several major achievements of 2015," Kerry wrote in an op-ed for the Boston Globe. "Of these, none is more important than the recent global agreement in Paris to prevent the most harmful impacts of climate change."

"We have a shared responsibility now to sustain the momentum generated in Paris, so that the targets established there are considered not a ceiling on what we can accomplish, but rather the platform upon which we can make further gains," he said.

Kerry listed the Iran nuclear agreement immediately after the climate deal in his op-ed. He repeated his announcement Monday that Iran has shipped out 25,000 pounds of low-enriched uranium, a major step toward implementation of that deal.

Kerry has been criticized by Republicans for focusing too much on climate, and not enough on more traditional State Department issues. Some said Kerry should have turned the Paris talks into a meeting about how to tame the Islamic State, since members of that terrorist group had just carried out an attack that killed 130 people.

After climate and Iran, Kerry listed the Obama administration's effort to reach out to Cuba as a third major initiative, followed by the Trans-Pacific Partnership trade deal. Most Republicans oppose both of these efforts as well.