The US Environmental Protection Agency has ratcheted up the pressure on ICAO's commercial aircraft carbon-dioxide emissions negotiations. A failure to reach an accord on an international standard for aircraft emissions by the February 2016 deadline is now even more likely to lead to the regulatory mess airlines have long feared—governments around the world imposing a patchwork quilt of unilateral rules.

EPA is part of the ICAO talks and emphasizes that its move in June—issuing a proposed finding that commercial aircraft CO2 emissions contribute to climate change and endanger public health—is in support of the ICAO process. Based on a 2007 US Supreme Court ruling that the 1970 Clean Air Act granted EPA the authority to regulate automobile CO2 emissions, EPA issued a formal finding in 2009 that greenhouse gasses including CO2 emissions “threaten the public health and welfare of the American people.” That finding led EPA to set new CO2 emissions standards for automobiles. Now EPA has taken what it calls a first step toward regulating aircraft CO2 emissions.

Under the Clean Air Act, EPA is obligated to address declared pollutants. As former EPA administrator Lisa Jackson put it, “Once you know you have a pollutant and you know it’s endangering public welfare, then EPA must act.”

Christopher Grundler, the director of EPA’s Office of Transportation and Air Quality, assured reporters EPA wants there to be an accord at ICAO, in which case a formal finding by EPA administrator Gina McCarthy that aircraft CO2 emissions are a pollutant would simply lead to EPA adopting the ICAO standard. “Our number one goal is to secure a meaningful international standard,” Grundler said.

That may be true, but the US has now set the wheels in motion, likely inexorably, to establishing a CO2 standard for commercial aircraft. If the ICAO talks fail, it would be hard for EPA to backtrack and say that aircraft CO2 emissions aren’t an endangering pollutant. Therefore, the US would probably move to act unilaterally if the ICAO talks blow up.

Remember, the February 2016 deadline for reaching an agreement at ICAO was essentially forced by the European Union threatening to impose its emissions trading scheme on non-EU aircraft operating into the EU. So a failure at ICAO could very well lead to both the EU and the US—as well as other nations around the world—setting their own commercial aircraft CO2 regulations. And if what’s decided at ICAO is considered feckless, environmental groups and others in the EU and the US are likely to apply pressure for unilateral standards tougher than ICAO’s.

So it’s critical that, by early next year, the nations negotiating at the UN’s civil aviation body come up with more than a superficial emissions pact or, worse, another agreement to reach a final agreement at a later date. The heat is on.