Cheers rose from prominent voices around the world this month when almost all countries agreed to reduce the climate costs of international air travel. The United Nations and White House applauded the deal, as did the airline industry and even some environmentalists. Yet the agreement hardly qualifies for the praise. It stands to do little to reduce carbon dioxide emissions from airplanes.

These emissions are certainly a problem. Airlines currently account for just 2 percent of global greenhouse gases. But if air travel continues to grow at its current rate, the carbon released will triple by 2050.

Yet this agreement, which is voluntary until 2027, sets no meaningful limits on that growth. It speaks of holding the damage at a level that won’t even be reached until 2020. Compare that with the Paris climate accords, by which the US committed to cutting emissions at least 26 percent below 2005 levels by 2025. (Other countries were even more ambitious.)

And the deal may not meet even its own low bar. Rather than make their aircrafts more fuel-efficient, airlines will be allowed to negate their post-2020 emissions growth on paper through the purchase of offsets -- for example, by paying to plant trees somewhere in the world.

The deal doesn’t say how the offsets will work, or what safeguards will exist to make sure they do. Even the most rigorous offset programs raise the risk of double-counting, awarding credit for carbon reductions that would have happened otherwise.

The signatories to the deal call the offsets a “market-based mechanism.” But it has nothing to do with the market for jet fuel. A true market-based mechanism would be a price on the carbon content of that fuel, accounting for its toll on the atmosphere. Such a price would give jet-fuel buyers -- the world’s airlines -- an incentive to use lighter, more efficient aircraft, to change their routes or adopt other fuel-saving policies.

Perhaps it is some mild progress that the International Civil Aviation Organization came up with a deal at all. But it doesn’t help to merely pretend to cut carbon emissions. The 191 member states would do better to return to the table and discuss the need for every country to put a meaningful price on carbon.

(Bloomberg)