Mention politicians in the same sentence with global warming, and the “hot air” jokes almost write themselves. Unfortunately, what world leaders have planned for us when it comes to climate change is no laughing matter.

Indeed, Americans have good reason to worry as international elites gather in Copenhagen this month to discuss their climate-change agenda. The greatest danger is that U.S. officials will sign on to a treaty that would put us at a huge economic disadvantage, yet do virtually nothing to affect the earth’s atmosphere.

Here’s how we got here.

In 1997, world leaders agreed to the Kyoto Protocol. The U.S. signed that document. But President Clinton never submitted it for Senate approval. Neither did President George W. Bush. So it never achieved the force of law here.

Under Kyoto, developed economies – including most of Europe, as well as Japan and Canada – promised to cut greenhouse gas emissions (mostly carbon dioxide from fossil fuels) by 5 percent below 1990 levels by 2012.

They haven’t kept that promise. In fact, the U.S. has done better as a Kyoto treaty outsider than many insiders.

U.N. statistics show our economy trimmed emissions by 3 percent from 2000 to 2006. The 27 European signers increased their emissions during those years slightly, with Austria, Finland, Greece, Ireland, Italy, Portugal and Spain leading the way. Canada, supposedly a poster child for green behavior, increased its emissions 21.3 percent.

Yet, even though their nations failed to meet Kyoto’s emission limits, many leaders want to see those standards made even more stringent at Copenhagen. And they want them to apply to the U.S. for the first time.

This is where our leaders must be careful. Other countries haven’t paid any legal price for failing to keep their promises. But the U.S. could.

American law, uniquely, can give a ratified treaty the same status as domestic legislation. So if the Senate were to ratify a global-warming treaty, American businesses must comply with it.

More than a decade ago the U.S. Senate made it very clear it wouldn’t ratify Kyoto. It passed the Byrd-Hagel resolution, 95-0, instructing the Clinton administration that it wouldn’t sign any treaty that exempted developing nations (China, India) or would harm the American economy. But would today’s lawmakers make such a sensible stand?

Perhaps not. Over the summer the House of Representatives passed the Waxman-Markey bill, a massive tax on energy production and use. A Heritage Foundation analysis showed that for a household of four, energy costs (electric, natural gas, gasoline expenses) would rise by $436 in 2012 and by $1,241 by 2035, averaging $829 over that period.

The bill also would weaken our economy. The Heritage analysis estimates the U.S. would lose 1 million jobs (on average) every year through 2035. And that’s counting the “green jobs” the bill would supposedly create.

A Senate committee recently signed off on a similar bill, named Kerry-Boxer. So while the entire Senate may still act sensibly and defeat this measure, it’s clear that the once overwhelming consensus against destroying our economy to combat the supposed threat of global warming is weaker than it once was.

Keep in mind that all this pain comes with virtually no gain. Global temperatures haven’t risen for a decade now. And at least one scientific study estimates that even if the world met Kyoto’s targets, global temperatures would be trimmed by just 0.07 degree Celsius by 2050, a difference too small to measure.

It’s no mystery why developing nations want to force us to comply with emission standards they’re exempt from. But that doesn’t mean U.S. policymakers should go along with this shackling of the American economy.

In Copenhagen, our negotiators should insist that individual nations focus on cutting emissions as they see fit. More importantly, they should make it clear that the U.S. isn’t about to wreck the world’s strongest economy just so we can sign a fashionable treaty.