Industries must decarbonize. For aviation, where only jet fuel can power such hulking machinery through the air, this is a harder challenge than for most. Though adopting more efficient planes and better routes has led to some carbon savings, airlines appear decades away from being able to make wholesale changes. Unlike shipping, which has slashed its carbon output by opting for cleaner fuels and more efficient technology, aviation is stuck. Renewable fuel is mostly too expensive or inefficient to be a realistic solution, while battery-powered planes that can carry more than about six people are still a long way off.

That doesn’t mean it shouldn’t try—after all, airplanes put disproportionately high amounts of carbon into the atmosphere. But until the technology improves, airlines making even the vaguest claims at some level of carbon neutrality, such as JetBlue, British Airways, and easyJet, have only one solution: carbon offsets, and lots of them. As airlines can’t directly reduce their own footprint, they must pay to cancel out more immediately shrinkable greenhouse gas emissions elsewhere in the world. (Hoping that people will simply give up flying doesn’t seem to be panning out.)

When individuals or companies purchase carbon offsets, they are helping to fund projects that either remove greenhouse gasses from the atmosphere, or prevent them from entering it. Because greenhouse gases mix quickly with the air in the atmosphere, and spread around the whole planet, it doesn’t especially matter where those reductions take place—what’s important is the net total of emissions in the atmosphere, or so the theory goes.

Climate experts around the world often describe offsets as a last resort, coming far behind adopting practices that actually reduce emissions. Offsets, they caution, cannot curb our growing emissions, especially since newly planted trees—a common offset—need time to grow. But for those emissions that can’t easily be reduced, offsets—provided they are either properly certified or traded in a regulated market (or both)—can be a reasonable transitional option, at least until something better comes along. They are, for now, aviation’s only recourse.

Show me the receipts

Environmental campaigners have a tendency to frame these carbon offsets in moral terms. George Monbiot, the Guardian columnist and political activist, puts it succinctly: “You buy yourself a clean conscience by paying someone else to undo the harm you are causing.” Offsets, he argues, are a modern-day equivalent to the indulgences once peddled by the Catholic church, permitting people to purchase “complacency, political apathy and self-satisfaction.” There are problems with this analysis, said Landon Brand, CEO of Project Wren, a company which sells offsets direct-to-consumers to counterbalance their personal carbon use. In the case of the Catholic church, there wasn’t really any specific activity that the church could do to “absolve” sin, says Brand. “With carbon, it’s different.” Assuming an accurate calculation of how much damage was done in the first place, he says, “it’s like they never touched the atmosphere.” Read the rest of article at Quartz