CO2 compensation alone does not make flying climate-friendly

Jet A-1, a The straw-colored, kerosene-based fuel used in most large aircraft is a difficult substance to replace. It’s full of energy; per unit weight at least 60 times as much as the lithium-ion batteries that power electric cars. It’s also terrible for the climate. As the airline industry has gradually made global pledges to eliminate carbon emissions, it has mostly promised to offset its damage elsewhere — through offset payments that include planting trees, restoring wetlands, or paying people to preserve ecosystems might include that would otherwise have been looped. But according to a growing body of research, these efforts are missing something: Most of the planet-warming effects of flying are not due to carbon dioxide.

Burning jet fuel at 35,000 feet triggers a molecular cascade in the troposphere. The initial combustion releases a shower of particles – sulphur, nitrogen oxides, soot and water vapour. At these frigid altitudes, some of the particles become nuclei around which condensation collects and then quickly freezes, helping to create swollen contrails that either disappear or persist as thin cirrus clouds at high altitude. In the presence of the sun’s rays, nitrogen molecules set in motion a chain of reactions that produce ozone and destroy free-floating atmospheric methane. It’s hard to pin down the meaning of all this chemistry. Some of these reactions, like methane destruction, help cool the Earth. Others warm it. It all depends on the atmospheric conditions for each flight, multiplied by the tens of thousands of planes hurtling across the sky each day.

Overall, the warming effects add up. In an analysis published last year, an international team of researchers attributed 3.5 percent of the total warming in 2011 to aviation alone — which may sound low, but the number is growing fast. The authors found that about two-thirds of the warming from air travel at that time was caused by all of these factors are not CO2 emissions.

That’s why some scientists argue that the term “carbon neutral” doesn’t mean much, at least when it comes to flying jets. If the aviation industry wants to do its part to meet global temperature targets, it’s better to think in terms.”climate-neutral», says Nicoletta Brazzola, climate policy researcher at ETH Zurich. In a study published in this week nature climate change, She outlines all the ways to get there, including rules for more efficient flying, new technologies like low-carbon fuels and batteries, and more intensive efforts to remove carbon from the air that would go beyond wiping out aviation’s CO22 -Emissions that make up all the warming effects of industry. And, oh yes: less flies. “It would take a huge effort to meet this carbon neutrality framework with just technological improvements and no lifestyle changes,” she says.

So far, the focus of the industry has been on CO2 compensation. It’s the greenhouse gas we all know, and it’s easy to measure how burning jet fuel converts to tons of carbon emissions. This is based on intimate knowledge of existing fuels and engines. Airlines are already doing these calculations and letting customers see their damage — often paying a little extra to offset those emissions through partner programs that do things like plant trees. Anticipating continued growth in aviation demand, members of the International Civil Aviation Organization (ICAO) have committed to maintaining their net carbon emissions at 2019 levels through this type of offsetting. These efforts themselves are far from perfect — a body of research has found that many of the offset programs airlines work with chronically overestimate the amount of carbon they are successfully storing. And again, these systems are all about carbon.

That’s partly because it’s difficult to account for all the non-CO2 factors. Atmospheric chemistry at 35,000 feet is inherently localized and dependent on factors such as temperature and humidity. The greatest uncertainty is the potential behavior of contrails – the tendrils that form behind aircraft when water molecules around exhaust particles condense and freeze. “The basic microphysics of ice crystals is quite difficult to get to grips with,” says David Lee, an atmospheric scientist at Manchester Metropolitan University who studies aviation emissions. If the air is humid and cool enough, they can hang around as cirrus clouds, and that would likely have a net warming effect. Time of day is another X factor. During the day, these clouds can reflect sunlight and keep the earth cool. But they can also store heat, especially at night.

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