In his second inaugural address, President Obama pledged that the United States “will respond to the threat of climate change” and will take the lead for other countries to follow suit.

This commitment is a willful rejection of reality.

Congress has been unwilling to address climate change unilaterally through legislation. Multilateral attempts become more futile each year as major players, especially developing nations such as China and India, refuse to play ball.

And why should they? Developing nations are not going to curb economic growth to solve a theoretical problem when their citizens face far more pressing environmental problems — especially when so many are trapped in grinding poverty and lack access to reliable electricity.

This leaves the president with only one option for making good on his pledge: impose costly regulatory actions. This approach would be as pointless as unilateral legislative action.

Why? Even accepting as fact the theory that Earth is warming and that carbon dioxide and other greenhouse gas emissions are a warming agent does not make any of the following true:

• Man-made emissions are driving climate change and are a negative externality that needs to be internalized. Greenhouse gas emissions are a warming agent. But that fact doesn’t begin to settle the scientific debate about climate change and climate sensitivity — the amount of warming projected from increased greenhouse gas emissions. Moreover, viewing man-made carbon dioxide as a strictly negative externality ignores a lot of peer-reviewed literature that identifies many positive effects (e.g., plant growth, human longevity, seed enrichment and less soil erosion as a result of more robust tree root growth) associated with higher levels of CO2 in the atmosphere.

• Earth is cooking at a catastrophic rate. The media breathlessly reported that a recent National Oceanic and Atmospheric Administration’s study found 2012 to be the warmest on record for the continental United States. What they largely failed to report was that, globally, 2012 was only the ninth-warmest in the past 34 years. In fact, average global temperatures have leveled off over the past decade and a half.

• Sea levels will rise dramatically, threatening America’s coastlines. The Intergovernmental Panel on Climate Change report, the bible of CO2-reduction proponents, projects sea levels rising 7 inches to 23 inches over the next century. That’s not as alarming as it sounds. Sea level has risen at the lower end of that projection over the past two centuries.

• There will be more extreme droughts, heat waves, hurricanes and other natural disasters. Natural disasters (they’re called “natural” for a reason, right?) will occur with or without increased man-made emissions.

Having failed repeatedly to win legislation limiting greenhouse gas emissions, the Obama administration appears bent on taking the regulatory route. The Environmental Protection Agency is promulgating stringent emission standards for new power plants that would effectively prohibit construction of coal-fired generators and prematurely shut down existing plants. The EPA also has introduced costly new air-quality standards for hydraulically fractured wells and new fuel-efficiency standards that will make cars and light-duty trucks more expensive, smaller and less safe.

Restricting greenhouse gas emissions, whether unilaterally or multilaterally, will impose huge costs on consumers and the U.S. economy as a whole. Congress should exercise its seldom-used muscles as regulatory watchdog to keep regulatory proposals that are not cost-effective from full implementation and reverse the administration’s course on regulating CO2.

As for the president’s suggestion that unilateral action by the U.S. will somehow inspire other countries to emulate our example — the repeated failure of U.N. negotiations to produce multilateral climate action demonstrates a near universal disinclination to sacrifice economic growth on the altar of global warming.

President Obama should respond to the threat of climate change by acknowledging that the severity of the threat is low and the costs of action are painfully high. And that unilateral action by the United States won’t make a dent in Earth’s temperature anyway.

-An economist specializing in energy and environmental issues, Nicolas Loris is the Heritage Foundation’s Herbert and Joyce Morgan Fellow.