Travel emissions

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Anze Slosar
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Affiliation: Brookhaven National Laboratory
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Re: Travel emissions

Post by Anze Slosar » March 06 2007

Antony Lewis wrote:It's true flights are currently responsible for a small fraction of the total. But aviation is expanding rapidly, aviation fuel is untaxed, and emissions are not included in any carbon trading schemes. For the small fraction of the population who fly far more than the average (I think about two flights per person per year in the UK), flights are a major component of their carbon footprint. That's many of us (myself included!).
I think that you really are a bit inconsistent here. As in any experiment, where you always try to get rid of the most important source of noise first, we should get rid of the most important CO2 emitters first. And if flights are currently at around 2% (I think, not sure) then we ignore them, until they become the major pollutant. Besides, ships for example, are currently emitting more that flights are and are also predicted to grow explosively. Undeveloped world is growing at extremely high pace and is likely to eclipse any CO2 savings you might make. So it is not clear at all which of these is going to be major in the future (a non inconceivable fluctuations in the oil prices in the next 20 years might change predictions completely). Bottom line is that flying less makes you feel better, but you really don't make much difference. But to be a really good person, you should try to make a difference, rather than feel better...
(By the same token I disagree with many UK charities, fair trade and organic food, but this exceeds this topic)

I think that this anti-flying campaigning stems from, in my view fallacious, thinking in terms of emissions per person. What the distribution of emission per person is doesn't matter at all, what matters is the overall emission. For example, as a clever physicist you could invent a good process innovation that would allow to cut emissions in some plant in underdeveloped world by half. Surely, if developing this innovation (or maybe developing it quicker) would require flying around the world 5 times, you would still be justified to do it, right? By the same token, you should identify the currently major pollutant *in the world, not UK* and invest your time in improving that by lobbying, thinking about technology, etc...

Antony Lewis
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Re: Travel emissions

Post by Antony Lewis » March 07 2007

I partly agree, but everyone has to try what they can realistically achieve - dreaming of better things and doing nothing is worse. What one individual does with their own emissions of course makes little difference - they will personally always be better off not cutting back on anything. The idea it to try to change the way things are done so *many* people are pushed into making reductions. I'm optimistically assuming governments will enforce massive reductions elsewhere; the main area that seems likely to be exempt, and growing most rapidly, is aviation- and this is something we can try to cut down on using as a community. If aviation is not curtained it'll wipe out many gains elsewhere.

Also note that if your innovation merely increases energy efficiency this might actually result in more total emissions.. (subtle point: making efficiency gains makes products cheaper, so sell more, so increase in emissions; also if you save money on energy there's a tendency for anything else you spend it on to be nearly as bad - I haven't yet got my head around what people should be spending their money on)

But if you have a brilliant way to save billions of tons of developing world production you have my full support...

Antony Lewis
Posts: 1941
Joined: September 23 2004
Affiliation: University of Sussex
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Re: Travel emissions

Post by Antony Lewis » April 26 2007

An update: sorry, there was a mistake in my earlier post
The current global average emission is about 1 tonne CO2 per year per person
should have been 5 tonnes CO2. I was confusing with the sustainable level, which is about 1 tonne each.

The UK now has a draft Climate Change Bill aiming for cuts to 60% of 1990 levels by 2050 EXCLUDING international aviation and shipping. If you factor in projected growth in aviation (planned by the government) the actual effective total cut in 2050 will only be 35-45% - way behind what is needed. (note how misleading the headline 60% number is - if you are in the UK I suggest you ask your MP to try to improve it). I can't find any information on whether the Californian target of 80% includes aviation or not, it seems to be pretty vague at the moment? But the bottom line is aviation is a big problem however you look at it.

There is a rather complicated issue of the global warming potential of aviation emissions because they are at high altitude and contain other non-CO2 gases. Here's a quick summary of what I read:There are short term effects due to clouds, medium term effects due to NOx (which have mixed sign because indirect ozone production can destroy methane), and long term effects due to CO2. The 1999 IPCC report calculates a radiative forcing factor of 2.7 (i.e warming effect per tonne CO2 emitted is equivalent to 2.7 tones pure CO2), but this is just an instantaneous measure of the daily heating effect now, which depends on the recent emission history because of the timescales involved. To calculate how bad extra aviation emissions are now you really want to integrate the different effects of a marginal emission now into the future to calculate some effective global warming potential [Ref Ref]. This then depends on the upper limit of the integral, with factors of may be about two over 20 years, but falling for longer baselines. But then you read about modelling uncertainties, and then you are glad you do cosmology! It seems no-one really understands the effect of cirrus clouds, and their effect could make aviation much worse than currently thought.

Finally, in case you think the marginal impact of one flight is unimportant: if you take Stern review projections for the additional number of people under severe food stress due to warming and calculate the fraction due to emissions from one flight, you get around 0.001. Assuming a time-scale of a lifetime this means roughly that one hour flying potentially causes one person to go hungry for an extra day. For people who prefer numbers the 'social cost of carbon' is defined by economists as an integrated marginal cost into the future discounted to the present: figures vary wildly, but may be around \$100 (i.e. medium-flights have hidden cost of about \$100). If we could fix offsetting mechanisms into travel budgets this imbalance could be partly redressed. But I think the most pressing issue is to cut aviation growth before it comes to dominate the emission budget.

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