Before the pandemic aviation was putting climate change on the agenda, or at least trying to get ahead of government restrictions.
Delta claimed they’d be carbon neutral starting in March, but this was mostly coming from buying carbon offsets which are dubious. United’s efforts center on biofuels, which at current technologies are too resource-intensive to scale. American Airlines just buys newer, more fuel-efficient planes.
It’s unclear how much passengers actually care about the environmental footprint of their travel. When given the choice they decline to buy carbon offsets (Catholic indulgences). Governments care, though.
It turns out what while aviation’s contribution to global emissions has been growing as worldwide air travel has grown (pre-pandemic), it hasn’t increased in relative importance. Between 2000 and 2018 aviation has steadily accounted for about 3.5% of climate-affecting emissions, and that includes commercial and cargo flights, according to a new study from climate scientist David Lee and Manchester Metropolitan University.
What’s especially interesting though is just how aviation appears to affect climate. It’s contrails that matter most – water vapor and exhaust forming ice crystals. And while this is the main pollutant, they’re only about half as much of a driver of warming than once believed.
Better still, they’re “the easiest” of what planes emit to reduce.
[T]he most cost-effective would be to change the altitudes of the 15 percent of (U.S.) flights that fly in conditions that lead to the formation of contrails. They estimate that a 2,000-foot increase in cruise altitude for those flights would reduce contrail impact by 62 percent, while a 4,000-foot increase would reduce it by 92 percent. This would require better meteorological data in flight planning, but its cost in terms of fuel burn and flight time would be small.
Hydrogen-based fuels won’t solve the contrails problem, which is the largest environmental challenge – but if these ever did scale airlines could fly at higher altitudes as a mitigation step, too.
As we learn more about the true environmental impact of travel, we’ll need a mix of strategies and need to start with the low hanging fruit. Sure, burning less fuel matters holding everything else equal. And using less-emitting fuels would be nice if they were technologically feasible. But there are easy things we can do now, as a bridge to a better technological future.