It's one of the world's fastest-growing sources of greenhouse gas pollution. If commercial aviation were considered a country, it would rank seventh after Germany in terms of carbon emissions.
So why has this sky-high source of planet-warming pollution suddenly and mysteriously vanished from the radar at international climate talks?
In the run-up to this year's Paris climate summit, negotiators from the United States and other nations have been crafting a document that will form the basis for a final global treaty.
Aviation and shipping have been addressed in that text since early on. Aviation's impacts account for some five percent of global warming, while shipping adds some three percent. Making the ambitious, economy-wide carbon cuts necessary to combat climate change without these sectors would be nearly impossible.
But negotiators have now abruptly abandoned their wise efforts to rein in transportation-related carbon emissions. Ships and planes -- and their fast-growing pollution -- have utterly disappeared from the just-released version of the negotiating text. Removing these sources from the text would exempt aviation and shipping from the Paris greenhouse gas reduction efforts.
The Obama administration's climate legacy is at stake. The U.S. EPA recently acknowledged that airplane emissions endanger our climate. Now, to safeguard our planet, State Department negotiators must get planes and ships back into the Paris climate agreement.
Fairness alone demands aviation and shipping be included. Why should these two highly polluting industries get to spew unlimited carbon, leaving other parts of the economy to pick up their slack?
Every country and every economic sector bears responsibility for cleaning up its act -- particularly when its emission growth outpaces those of others. Global aviation carbon emissions are estimated to triple by 2050, making aircraft pollution one of the fastest-growing contributors to climate change. Shipping emissions are not far behind: They are projected to grow as much as 250 percent by 2050.
Fairness aside, leaving these two pollution sources out of the Paris negotiations risks undermining these talks before they've even truly begun.
Even if every new emissions reduction pledged by countries this year is actually implemented, the Earth will still suffer a whopping 6.3 degrees Fahrenheit of warming by century's end. It's clear that we must quickly implement more ambitious cuts, and critical that every industry step up. Allowing aviation and shipping to skip the process, while doubling or tripling their emissions, undermines efforts by other sectors such as the auto industry and trucking -- all of whom should be crying foul.
Airlines and shipping companies, of course, have long argued they should be left to pursue voluntary climate efforts, and they've used lobbying muscle to crush sensible attempts to regulate their emissions.
These industries have even co-opted the specialized international agencies in charge of overseeing their global pollution standards. The International Civil Aviation Organization, for example, has failed for 18 years to adopt any measure to curb aircraft-induced global warming. So far the organization has rejected, in turn, efficiency standards, fuel taxes, emissions charges and global emissions trading.
Without oversight, shipping and aviation will do next to nothing to contribute to a global climate change solution. That's why removing these industries from the Paris agreement was a dangerous mistake.
But there's still time to put them back in -- especially if the Obama administration and European governments push for their inclusion. As global warming's threat grows, we simply can't afford an international climate treaty that gives these two irresponsible industries a free pass to pollute.