Carbon offsets alone will not make aviation climate-friendly | MarketingwithAnoy

Jet A-1, a straw-colored, petroleum-based fuel used in most large aircraft is a difficult substance to replace. It is packed with energy; unit of weight, at least 60 times as much as the lithium-ion batteries used to power electric cars. It is also terrible for the climate. So as the aviation industry has gradually gotten on board with global pledges to get rid of carbon emissions, it has mostly promised to make up for its damages elsewhere — through offsets that might involve planting trees, restoring wetlands or paying people for to preserve ecosystems that would otherwise have been razed. But according to a growing body of research, these efforts are missing something: Most of the planet-warming effects of flying are not from carbon dioxide.

Burning jet fuel at 35,000 feet triggers a molecular cascade in the troposphere. The first combustion releases a flurry of particles – sulphur, nitrogen oxides, soot and water vapour. At these cold altitudes, some of the particles nucleate around which condensation collects and then quickly freezes, helping to produce raised bottom features that either disappear or persist as wispy high-altitude cirrus clouds. In the presence of the sun’s rays, nitrogen molecules set off a chain of reactions that produce ozone and destroy free-floating atmospheric methane. It is difficult to determine the meaning of all this chemistry. Some of these reactions, like the methane breakdown, help cool the Earth. Others heat it. It all depends on the atmospheric conditions for each flight, multiplied by the tens of thousands of planes that streak across the sky every day.

Overall, the warming effects add up. IN an analysis published last year, an international team of researchers pegged 3.5 percent of total warming in 2011 from aviation alone—which may sound small, but the number has grown rapidly. The authors found that about two-thirds of the warming due to aviation at the time was caused by all the factors that is it 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 help meet global temperature targets, it’s even better to think in “climate-neutral,” says Nicoletta Brazzola, climate policy researcher at ETH Zurich. In a study released this week in nature climate change, she outlines all the ways to get there, including regulations 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 eliminating aviation’s CO22 emissions that account for all the warming effects of industry. And, oh yes: less flying. “It would take a huge effort to meet this climate neutrality framework with just technology fixes and no lifestyle changes,” she says.

So far, the industry’s focus has been on offsetting carbon. It’s the greenhouse gas we all know, and it’s easy enough to measure how burning jet fuel turns into tons of carbon emissions. It is based on in-depth knowledge of existing fuels and engines. Airlines already do these calculations and let customers see their damages—and often pay a little extra to offset those emissions through partner programs that do things like plant trees. In anticipation of continued growth in aviation demand, members of the International Civil Aviation Organization (ICAO) have pledged to keep their net CO2 emissions at 2019 levels through these types of offsets. The effort itself is far from perfect –-one number of surveys has found that many of the offset programs that airlines partner with chronically overestimate the amount of carbon they are successfully sequestering. And again, these schemes are about carbon.

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

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