Shaun Hendy – How Much does Flying Contribute to Climate Change?

The Conversation

Planes can create clouds of tiny ice crystals, called contrails, and some studies suggest they could have an a significant effect on climate.
from, CC BY-ND

Shaun Hendy, University of Auckland

The flight shaming movement has raised our awareness of air travel’s contribution to climate change. With all the discussion, you might be surprised to learn that air travel globally only accounts for about 3% of the warming human activities are causing. Why all the fuss?

Before I explain, I should come clean. I am writing this on the train from Christchurch to Kaikoura, where I will give a talk about my recent book #NoFly: walking the talk on climate change. I have some skin in this game.

Staying grounded

Taking a train around New Zealand is no mean feat. In the North Island, the train between Auckland and Wellington runs only every second day. If you get off at a stop along the way, you have to wait another two days to continue your journey. You can catch a bus, but you’ll spend that bus journey fantasising about the possibility of an overnight train service.

So why do it? A good deal of global carbon emissions come from industrial processes or electricity generation under the control of governments and corporations, rather than individual citizens. For many of us, a decision not to fly might be the most significant reduction in emissions we can make as individuals.

As Swedish climate activist Greta Thunberg has shown, refusing to fly also sends a powerful signal to others, by showing that you are willing to change your own behaviour. Politicians and corporate sales departments will take note if we start acting together.

Impacts of aviation

Aviation affects the climate in a variety of ways.

Because any carbon dioxide you emit stays in the atmosphere for hundreds of years, it doesn’t matter much whether you release it from the exhaust pipe of your car at sea level or from a jet engine several kilometres high. Per passenger, a flight from Auckland to Wellington will put a similar amount of carbon dioxide into the air as driving solo in your car. Catching the train will cut your carbon emissions seven-fold.

When aircraft burn jet fuel, however, they also emit short-lived gases like nitrogen oxides, which can react with other gases in the air within a day of being released. When nitrogen oxides are released at altitude they can react with oxygen to put more ozone into the air, but can also remove methane.

Ozone and methane are both greenhouse gases, so this chain of chemical reactions can lead to both heating and cooling effects. Unfortunately the net result when these processes are added together is to drive more warming.

Depending on the atmospheric conditions, aircraft can also create contrails: clouds of tiny ice crystals. The science is not as clear cut on how contrails influence the climate, but some studies suggest they could have an effect as significant as the carbon dioxide released during a flight.

There is also considerable uncertainty as to whether aircraft exhaust might affect cloud formation itself – this could be a further significant contribution to warming.

Growing demand for air travel

Offsetting, by planting trees or restoring natural wildlands, will take carbon dioxide back out of the atmosphere. But we would have to do this on a massive scale to feed our appetite for flight.

Emissions from international air travel are not included in the Paris Agreement, although the United Nations has been working on the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), which may begin to deal with these. Initially, the scheme will be voluntary. Airlines flying routes between countries that join the scheme will have to offset any emissions above 2020 levels from January 2021.

Emissions from flying stand to triple by 2050 if demand for air travel continues to grow. Even if air travel became carbon neutral through the use of biofuels or electric planes, the effects from contrails and interactions with clouds mean that flying may never be climate neutral.

With no easy fixes on the horizon, many people are thinking hard about their need to fly. This is why I took a year off air travel (alongside my colleague Quentin Atkinson) in 2018.

I have been back on planes in 2019, but I have learned how to reduce my flying, by combining trips and making better use of video conferencing.

Fly if you must, offset if you can, but – if you are concerned about climate change – one of the best things you could choose to do is to fly less.

Shaun Hendy, Professor of Physics, University of Auckland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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1 Comment

  1. The author here is rather hedging his bets as whether aircraft actually contribute to global warming. 3% of AGW is an unknown until we know how much, if any, warming of the atmosphere is due to (un)economic activity by people. So it appears, compared to many an academic, scientific or technical article treating of global warming, a balanced approach.
    To protect the natural environment, so much more important while mankind persists, common sense and honesty in politics is a high priority, if not the highest priority. Thus far, since, to put it into a time frame, roughly the 1970s, the use of common sense and honesty has been increasingly under attack not only in politics, but also in finance, commerce, the Academe and in science. As a result increasing numbers of well-informed people who have the time and inclination to think things over have had their levels of critical opinionating and scepticism in the face of claims made by peer-appointed and/or peer-consensualy approved so-called experts to unprecedented high levels. The fact that there is almost without exception money to be made by pushing a certain agenda or stipends, research grants, salaries, etc, etc., lost if a certain agenda is not promoted, or not promoted with enough vigour colours the basis on which certain claims by “experts” are being made. One could say that more and more issues which in the relatively recent past would be decided by neutral, to a degree, people with knowledge specific to the matter in question are now increasingly drawn into the field of political gaming in an increasingly questionable contentious manner. Whereas in the past, when the majority of people were of a religious persuasion, or at least under the influence of superstitious thinking, church and state were one, or at least connected in such a way that the experts in religious thinking were influencing political issues to a large extent. Following the advent of democracy, sort of, the separation of Church and State became a fact, in theory. Before we in the nominally democratic West have weaned ourselves from the now increasingly faithful dug offered by mother church and its offshoots we find that we need to look at ways to separate High Finance and State, Commerce and State, the Academe and State, the Sciences and State, the Judiciary and State, the Bureaucracy and State, Allopathic Medicine and State, the Psychological and Psychiatric Arts and State, the Arts and State and last but not least, the high blown academic art of faux philosophy. There is a bit of work cut out for democrats-and not only in the western democracies, so-called, but in those countries elsewhere smitten by the democratic ideal.
    What can we do to save the natural environment? (Never mind the climate. That is a natural self-regulating system of such fiendish complexity any theory about its workings will not easily be proven wrong by any, least of all the scientific, method. Proving a scientific theory about the world’s climate will be even more unlikely. There are too many incalculable variables. However,… If fossil fuel use is the problem bugging certain people, worried as they claim to be, and for all we know genuinely are, about humanity surviving a changing climate, they could perchance start looking for ways to reduce their own carbon footprint. Next, some deep thinking is required by these concerned people as to what needs to be done for society to reduce the use of fossil fuels.
    I have some ideas. Taking the bus or train if it is too far to cycle. Always use the cheapest option, if money needs to be spent. The more one spends, the more money is available for others to spend it. Reduce gratuitous travel and expenses to a modest percentage of living expenses. Live modestly, if not frugally. If frugality is not your things, try at least to live on a income that is well below the average for the country where you earn your living. If you don’t earn your living, but rely on a sinecure or academic stipend, woe unto you if you perforce presume to tell other people how to live. To be a political agitator seeking to introduce higher charges, higher taxes, higher rates, higher levies or new imposts on account of AGW aka climate change, when the extra moneys thus extracted from the populace will inevitably lead to more uneconomic activity, or more economic activity, even, which leads to a greater use of fossil fuels, even if it is in the service of renewable, which are not yet economic, hence cost more, hence lead to extra burning of fossil fuels, now, that would be counter-intuitive, hypocritical even. On the other hand, if the politics of climate change and its train of political derivatives leads to economic stagnation, that would give countries which stand aloof from this kind of politics the advantage economically and, of course, financially. Countries which are yet to reach the level of consumerist debauchery currently all the rage in the West need not bother about climate change. The people in these emerging economies have been doing it tough since, since, well, since always. These people are not weakened by easy living and desk-bound occupations. They will survive. Well might their leaders think, if you can’t stand the heat, get out of the kitchen. It’s survival of the fittest, not the fattest.

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