The Environmental Protection Agency’s new proposed rules, which seek to limit carbon emissions from power plants, would cost the American economy $51 billion, as well as 224,000 jobs, every year through 2030, the U.S. Chamber of Commerce estimates.

With that significant of an economic impact, one would hope the EPA had a pretty good justification, right?

But I write today:

As the Cato Institute recently noted, the agency forgot to include one very important calculation in the information they released about the proposed rules: whether or not they will actually affect climate change.

“There’s really no reason to go after carbon emissions unless you think they cause climate change,” Chip Knappenberger, assistant director for Cato’s Center for the Study of Science, tells me. The impact on climate change is key. But the EPA hasn’t publicized any finding on that supposed link.

Knappenberger and his colleague Patrick J. Michaels crunched the numbers using an EPA-developed climate-model emulator. They found that the regulations would somewhat affect the climate — by eighteen-thousandths of a degree Celsius by 2100.

“We’re not even sure how to put such a small number into practical terms, because, basically, the number is so small as to be undetectable,” Knappenberg and Michaels wrote when they released their findings. “Which, no doubt, is why it’s not included in the EPA Fact Sheets. It is not too small, however, that it shouldn’t play a huge role in every and all discussions of the new regulations.”

That’s not the only time the EPA has used some suspect math. A new report from the Government Accountability Office found that the EPA was calculating how its regulations would affect employment using a study outdated by 20 years that had, even when current, looked at only four industrial sectors. You can read about even more about the agency’s number-fudging here.

— Jillian Kay Melchior writes for National Review as a Thomas L. Rhodes Fellow for the Franklin Center. She is also a senior fellow at the Independent Women’s Forum.