Murray Energy Chairman and CEO Robert Murray on Friday claimed global warming is a hoax and repeated a debunked claim that the phenomenon cannot exist because the Earth's surface is cooling.

Murray appeared on CNBC's "Squawk Box" to discuss Republicans' rollback of an Obama-era rule that would have restricted coal mining near waterways. President Donald Trump signed the measure on Thursday in front of Murray and a group of Murray Energy workers.

Murray Energy is the country's largest coal miner. Many of its mines are in Appalachia, a region that would suffer some of the biggest impacts of the rule. Murray also successfully sued to delay implementation of the Clean Power Plan, which would regulate planet-warming carbon emissions from power plants.

Asked about the economic analysis behind President Barack Obama's energy regulations, Murray said, "There's no scientific analysis either. I have 4,000 scientists that tell me global warming is a hoax. The Earth has cooled for 20 years."

It was not immediately clear who the 4,000 scientists Murray referenced are.