President Obama's environment chief said Tuesday an international agreement to phase out a globe-warming refrigerant chemical came together because it’s a low-cost way to combat climate change.

Nearly 200 nations, including the United States, agreed last weekend to a binding deal phasing out hydrofluorocarbons (HFCs), a potential greenhouse gas category used in refrigeration and air conditioning.

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Speaking with Mashable on Tuesday, Environmental Protection Agency (EPA) Administrator Gina McCarthy Regina (Gina) McCarthyFormer EPA chiefs endorse Biden, criticize agency direction under Trump OVERNIGHT ENERGY: Energy Department proposes showerhead standards rollback after Trump complaints | Interior memo scaling back bird protections is 'contrary to law,' court rules | Former EPA chiefs call for agency 'reset' Former EPA chiefs call for agency 'reset' MORE said the deal came together because negotiators found it a cheaper and easier way to reduce greenhouse gases than simply cutting carbon dioxide emissions globally.

“If we didn’t do that, we would have to replace all those additions with additional CO2 reductions,” she said. “That would be much more costly than actually addressing HFCs quickly and effectively.”

HFCs have about 10,000 times more global warming potential than carbon dioxide. The deal to phase down their use is expected to avoid 0.5 degrees Celsius of warming by 2100.

American officials and industry groups in the United States support phasing out the chemical, but negotiators needed to convince several developing countries to agree to do so as well.

India, which has growing demand for air conditioning, was one of the major hold-outs heading into last week’s conference in Kigali, Rwanda. But by the end of the week, Indian officials had agreed to phase down the chemical, but on a later timeline than for major nations like the U.S.

“We had to be flexible enough in the tailoring of the final agreement to recognize where India was, and what a real commitment they were making in the timeframe they were committing to,” McCarthy said.

The HFC agreement comes after a busy month on the climate front.

Earlier this month, enough countries ratified the Paris climate deal to ensure it takes affect this year. The agreement aims to reduce worldwide greenhouse gas emissions.

Also this month, the United Nations International Civil Aviation Organization agreed to an emissions trading system for international commercial flights, a move to reduce emissions from that sector.

McCarthy called the work “remarkable” on Tuesday.

She addressed other subjects as well. As others in the Obama administration had done, she dismissed the “keep it in the ground” movement that aims to end fossil fuel development as “fine,” but one that won’t be effective right now.

"I think it’s fine," she said. "Do i think it’s can happen right away? No, but that’s never stopped the environmental movement before. What the heck, they can keep pushing and we can keep responding."

And she said she has given up trying to win over people who deny the science behind man-made climate change.

“I would waste no time with climate deniers. If they haven’t figured out by now, what in God’s name can anyone say to them that would make them figure it out?” she said.

“I know that I’m supported to be for everybody, but my patience has worn thin over 8 years [in the Obama administration,] and 20 years before that trying to working on this.”