Globally, the industry generates roughly 1 billion tons of CO2 per year, which is comparable to Japan, the world’s third-largest economy. Moreover, emissions from flights have been rising by about 2.5% each year. Without bold solutions, the industry is on track to, over the next 30 years, produce more CO2 than that in its whole history.
In fact, the warming effects of contrails are still poorly understood by climate scientists and therefore given little attention by industry and governments working on decarbonizing aviation. It’s possible that the effects are small and could be largely managed by rerouting aircraft around the weather conditions that generate the worst contrails. But the effects could also be massive — up to half the total climate impact of aviation, according to some studies — and require entirely new aviation technologies and approaches to cutting the impact of aviation on the climate.
The study argues that addressing contrails may require profound overhauling of engines, airframes, and onboard storage — big, costly, and financially risky decisions. The authors urge more experimentation to test what really could work — backed by government policies and industry collaborations.
Resistance to efforts disruptive to the industry’s status quo is understandable because airlines often operate on razor-thin margins. A growing number of airlines want to do something about climate but are stuck with few practical options.
While renewable energy has scaled up to replace fossil fuels in power generation and both supply and demand for electric vehicles continue to increase, no carbon-free replacement technologies exist at an adequate scale to address pollution from aircraft.
The Nature piece comes ahead of the assembly of the International Civil Aviation Organization (ICAO) in Montreal, Canada, from Sept. 27 to Oct. 7, where representatives from 193 nations will try to negotiate an industry-wide target for cutting emissions from the sector.
Carbon offsetting is a reduction or removal of emissions of greenhouse gases (e.g., through land restoration or the planting of trees) that is used to compensate for emissions that occur elsewhere. According to the authors, the track record of reliable accounting in these industries is poor.
On the other hand, cleaner aviation fuel, which currently comes from conventional biofuel feedstocks such as vegetable oils, may be impossible to produce sustainably in sufficient volumes and at low enough prices to replace all jet fuel. Achieving the levels of clean fuel adoption that many governments and firms aim for — and doing so sustainably — will require commercializing new production methods and feedstocks that are still technologically in their infancy.
And neither of these solutions is sure to address the climate impacts of contrails, which trap heat radiating from the earth’s surface, causing warming in the atmosphere.