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By Sherry Listgarten

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About this blog: Climate change, despite its outsized impact on the planet, is still an abstract concept to many of us. That needs to change. My hope is that readers of this blog will develop a better understanding of how our climate is evolving a...  (More)

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Flying: How to lower your impact

Uploaded: Feb 23, 2020
I expect a lot of you felt like this after reading the previous blog post on flying...


The good news is, when you do fly, you can make it less bad for the planet, and there are a couple of ways to do that. I’ll start with the ones that make the biggest difference and work my way down. I expect many will be familiar, but I’ll try to provide some background on these suggestions that you may not have seen.

Fly Economy. This is easier said than done for bigger people and for longer trips, but I include it because larger seats mean more emissions per passenger, and some of the seats are pretty luxe.


Business class on Philippine Airlines

This choice makes a bigger difference than anything else I can find, so I list it first.

The estimates I have seen suggest the following overhead, but there is some variation based on the plane’s configuration:
- Premium economy: 30–50% more space
- Business class: 200–300% more space
- First class: 250%–400% more space (and can go higher)

If you do buy a premium seat, consider incorporating that overhead into your offsets (see next section).

Offset Properly. Buying offsets is not as reliable a way to reduce your flight emissions as skipping one or more flights, but there are some steps you can take to improve your offsetting: (1) Use a decent flight offset calculator. (2) Account for your seat class. (3) Account for non-CO2 impact. (4) Buy good offsets.

1. If you do a Google search for “carbon footprint calculator”, one of the top results is the EPA’s calculator. Unfortunately, it covers only three things: home energy use, car use, and (strangely) recycling. Take a look at it — it’s kind of fascinating in a “We paid for this?” sense — but don’t use it, since you won’t find air travel there! Virtually any other calculator will have an entry for flights. The top result I get is CarbonFootprint, which works fine, and several airlines have calculators, including United, Delta, and Virgin Atlantic. The calculators I’ve checked generally agree on flight distances and CO2 emissions, so these are all good choices.

2. Next, remember to multiply by the appropriate “premium seating” factor if you are not flying economy and the calculator does not ask you which class you are flying.

3. Third, double your miles to account for non-CO2 emissions. The only calculator listed above that incorporates these is the Carbon Footprint calculator. The Atmosfair calculator does as well. But most will not — they cover only CO2 emissions.

In case you are rolling your eyes at this multiplier, consider the chart below.


Ways in which aviation warms the planet. Source: CarbonBrief

The topmost red bar shows the impact of a flight’s CO2 emissions. The second-to-last line shows the sum of the other warming (and cooling) impacts except the one just above it (“induced cirrus”), which has very low certainty. You can see that the net effect is twice the size of CO2 on its own. Because of this, a multiplier of 2 to incorporate non-CO2 emissions is generally accepted, though Atmosfair uses a factor of 3 to account for the potential impact of high-elevation flights on cirrus clouds. You can learn more from this CarbonBrief writeup, or see this presentation by an expert in the field from early last year.

4. Finally, purchase quality offsets. I covered that in an earlier post. From what I can tell, the airlines that offer offsets do an okay job selecting them, so you can use those, or purchase some separately if there is a project of particular interest you want to support.

As an example of all this, suppose you are flying round-trip from SFO to London on United to attend your niece’s wedding. You are 6’2” and have a strong preference for business class. Most calculators will tell you that this is about 10,700 miles, with about 1.5 tons of CO2 emissions. You would then multiply by 2.5 for business class, and 2 for non-CO2 emissions, for a total of 7.5 tons of CO2. (1) You look for some Gold Standard offsets that also improve childrens health (e.g., cleaner stoves), which you find for around $10/ton. This costs you about $75, or around 1% of the cost of your business class flight. If you choose to squeeze into Economy, your flight would be much cheaper and your offsets would be around $30, or about 4% of the cost of your flight. (2) These offsets will hopefully reduce CO2 emissions somewhere in the world by the same amount that your flight is adding.

Note: Atmosfair is an interesting carbon footprint calculator. It shows you separate emissions estimates for common airlines, and even allows you to enter the type of plane you are flying. It also does things like apply the non-CO2 impacts only for the high-altitude portions of a flight. But using it to buy offsets can be more expensive, in part because it adds 200% for the non-CO2 emissions instead of the more standard 100%, and in part because the offsets themselves are somewhat expensive. Its estimate for the above business class trip is 7 tons of CO2 and $175 for the offsets. I think it’s a great site to use as a calculator, but you may want to purchase the offsets elsewhere.

Choose Lower Impact Flights. Flights are not all equal. You can lower your flight’s warming impact by avoiding short hops, preferring newer planes, and flying during the day. I’ll take those one at a time.

1. Avoid short hops. As you can see in the chart below, using the red line and the right axis (carbon intensity), a single 3000-mile flight emits less than multiple shorter flights. Two 1500-mile flights might have a carbon intensity of 85, while a single 3000-mile flight might have a carbon intensity of 75, almost a 15% reduction. This is partly due to extra fuel used at takeoff, and partly because less efficient jets may be used for shorter hops. Flying seems to be optimized around “medium-haul” distances of several thousand miles.


The red line shows the carbon intensity of flights for the year 2018, with shorter flights (to the left) generating more emissions per mile. Source: The International Council on Clean Transportation

2. Fly newer planes. If you look at the data generally, newer planes get around 90 mpg, while older ones get around 75 mpg (per seat). That is a 20% improvement, so not too shabby, but it’s not obvious how to book seats on newer planes. It may be easier to just fly airlines that tend to fly newer planes. The diagram below shows overall fuel efficiency for US domestic operations for 2017–1018.


Source: The International Council on Clean Transportation report for 2017–2018

That chart conflates a number of factors, though, including how much premium seating is offered, how many empty seats there are, and how efficient the planes are. This table breaks it down.


Source: The International Council on Clean Transportation report for 2017–2018

You can see that Southwest, for example, is a good option because it has few premium seats and it flies efficient planes. But I would say Hawaiian is also good if you fly Economy.

The chart below shows similar data for a selection of international flights.


Source: The International Council on Clean Transportation report for 2017

If this seems a little complicated (ahem), the Atmosfair calculator seems to take all of this and more into account, so you could also look there before booking your flight. Going to Hawaii from SFO? It recommends Hawaiian or United, but not Delta. The difference is almost 15%.

3. Fly during the day. This suggestion applies mainly to longer flights (2000 miles or more). Contrails are a big component of the non-CO2 impact of flights at high elevations. They reflect sunlight back up (which is good), but they also reflect heat back down (which is bad). Overall, they have an insulating effect, and that effect is biggest when they aren’t reflecting much sun, which is… at night! A 2006 study reports that although only a quarter of flights are at night, those flights account for 60-80% of all of the contrail warming impact from planes. That same study also indicates that contrails are less likely to form in the warmer summer months, so planning an annual longer-distance vacation in summer rather than winter can help as well.

All that said, some of the above is too complicated for me. But economy seating and offsetting work for me, as well as avoiding short hops and checking Atmosfair. Learning about this also helped me to appreciate the efficiency of more crowded flights, so I won’t mind those as much any more. In the next post on flying, I will review some of the technical innovations in green aviation. Will tech come to the rescue? First, though, I’ll take a detour into something a little more fun that I think many of you will relate to.

Notes and References
1. If you check the Global Carbon Atlas you will see that this one flight is almost a full year’s worth of (consumption) emissions for an average European (8.2 tCO2/person in 2017), or 42% of the emissions of an average American (18 tCO2/person).

2. I suppose another even simpler way to offset is to just purchase offsets worth 5% of your flight price. That would have made for a really short post, though :)

3. Another take on airline brands, besides fuel efficiency, is to look at how much their management seems to care about environmental impact. Are they reporting verified emissions data, setting long-term reduction targets, aligning corporate structure and incentives with climate initiatives, etc? A research institute at the London School of Economics has done a report on that (summarized by CNN, and with a presentation here). They indicate that ANA Group, Delta, Lufthansa, and United have pretty strong management focus on climate impacts. Both Delta and JetBlue recently made some pro-environment announcements, as did United 18 months ago. But Forbes has an interesting analysis of the substance of those promises that I tend to agree with.

Current Climate Data (January 2020)
Global impacts, US impacts, CO2 metric, Climate dashboard (updated annually)

Efforts to inhibit the spread of coronavirus, such as reducing air travel and generally staying at home, are also affecting China’s emissions. The two charts from CarbonBrief below show some relevant indicators. The first shows how coal used for power generation has not bounced back from the annual holiday drop, while the second shows levels of nitrogen dioxide, a byproduct of fossil fuel combustion, similarly staying low over that region.


Coal used for power in China before and after the New Year holiday, with 2019 in red. Source: CarbonBrief


Nitrogen dioxide levels over China have remained low after the New Year holiday. Source: CarbonBrief

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Comments

 +   17 people like this
Posted by neighbor, a resident of Midtown,
on Feb 23, 2020 at 11:47 am

ugh, not offsets again. sherry, you generally do such great/fantastic work - but offsets simply postpone the day of reckoning, no? 1st worlders, like me and you, continue to create lethal pollution with our "normal" lifestyles (oil 'n' gas automobiles, cheeseburger milkshakes, airplane trips) while paying for indulgences (offsets)...

as bill mckibben noted, slow/small "progress" means more death, disease and destruction. instead of writing about economy seats, how about a piece on the flight-shame movement?

it's easy to pontificate, i know. my sister works as a flight attendant, my brother's wife's family includes two pilots, my daughter's boyfriend's family are cattle ranchers. life is complicated.

i appreciate your blog even when i disagree; thanks again.


 +   23 people like this
Posted by Virtue, a resident of Another Palo Alto neighborhood,
on Feb 23, 2020 at 4:11 pm

Flying is not bad. It is up to the individual to decide whether to fly or not or whether to buy “offsets or not. Palo Alto has always tried to be the epicenter for virtue signaling regarding the environment. Now we have this blog with its endless lecturing on the “evils" of flying- telling the unwashed masses that we know better and you should no longer fly to see your family, for business or vacation.


 +   16 people like this
Posted by Virtue, a resident of Another Palo Alto neighborhood,
on Feb 23, 2020 at 4:14 pm

And if you are going to engage in guilt tripping and virtue signaling, you should at least know that Wow air and Thomas cook air both went bankrupt and shut down last year.


 +   13 people like this
Posted by What's my line?, a resident of Adobe-Meadow,
on Feb 23, 2020 at 6:24 pm

Let me guess - he's the same denier that posts under multiple names, as in the last thread?

Also - fascinating graph on Chinese coal use. Is China's overall coal use also declining as a percentage of their energy production?


 +   9 people like this
Posted by Sherry Listgarten, a Palo Alto Online blogger,
on Feb 24, 2020 at 12:10 pm

Sherry Listgarten is a registered user.

@neighbor. IMO, offsets are bad policy and are not scalable. But if you are going to fly, they are better than nothing. The question is, do they give people undue false comfort? I’d guess yes, to some extent. As you say, this is a very tough issue. I think it’s no coincidence that the EPA left flying and beef out of its carbon footprint calculator.

@Virtue. FWIW, I would have preferred to say “bad for the planet” in that meme, but it was too long, and I figured it was just a meme.

@What’s. The changes I show for China are a result of their shutting down much of their economy to try to inhibit the spread of coronavirus. But to answer your question, China is using proportionately less coal for energy than it used to: 59% in 2018 vs 68% in 2012, forecast to be 55% in 2020 (from Reuters). For reference, coal’s share of energy production in the US is about 27%, and virtually zero in CA. But China’s total coal capacity is growing, even though the relative proportion is shrinking, because their energy production is growing as their economy expands.


 +   7 people like this
Posted by Anon, a resident of Another Palo Alto neighborhood,
on Feb 24, 2020 at 2:31 pm

Posted by Sherry Listgarten, a Palo Alto Online blogger,

>> @neighbor. IMO, offsets are bad policy and are not scalable. But if you are going to fly, they are better than nothing.

I would look at this differently. Offsets absolutely are not scalable indefinitely, so, people should not think (does anyone?) that people can keep using fossil fuels indefinitely and make up for them with offsets. OTOH, there are biological carbon reservoirs that are in desperate need of protective money and protective policies, and, some carbon-offset programs are directed there. Example: Web Link


 +   8 people like this
Posted by Nancy G, a resident of Atherton: West Atherton,
on Feb 25, 2020 at 8:18 am

Hi Sherry, kudos to you for rising above the snarky comments and continuing to do your excellent work. Carbon offsetting is indeed a fraught topic and I think you handled it well, putting it in context of a lot of other considerations about the climate impact of flying. I was a little surprised you didn't delve more into types of offsets. As you no doubt know there has been a running debate, mostly between NRDC (which maintains several large reforestation projects in Brazil) and ProPublica, which did an expose last year purporting to demonstrate no impact of these types of projects. There was also an EU-funded study looking at different types of offsets within the regulatory market and finding those that were most likely to demonstrate leakage and least likely to prove additionality. What they found were methane digesters came out on top and reforestation and renewable projects came out at the bottom, ie, most likely "to have been done anyway" without the input of offset dollars. I don't know of any references evaluating this at the voluntary market level, which is of course what we all participate in. Anyway, if you ever decide to "go here" I've got a bunch of references.


 +   4 people like this
Posted by Anon, a resident of Another Palo Alto neighborhood,
on Feb 25, 2020 at 10:40 am

Posted by Nancy G, a resident of Atherton: West Atherton,

>> Carbon offsetting is indeed a fraught topic

>> ProPublica, which did an expose last year purporting to demonstrate no impact of these types of projects.

The question for me is, are there legitimate projects that are actually reversing damage to mangrove forests (and nearby rainforests0, that we can safely contribute to at the $100 contribution level, and get $90+ worth of benefit? Like many people, I'm extremely concerned about mangrove forests. We all need better channels to contribute directly to the health of these forests. Web Link


 +   4 people like this
Posted by diesel, a resident of another community,
on Feb 25, 2020 at 12:45 pm

diesel is a registered user.

Wow! Thank you for this. Lots of detail and it's going to take a couple of readings,but I appreciate your explanations and holding this discussion.


 +   5 people like this
Posted by Sherry Listgarten, a Palo Alto Online blogger,
on Feb 25, 2020 at 12:58 pm

Sherry Listgarten is a registered user.

@Nancy: Thanks for the comment! I did at least try to write about offsets a few weeks ago here. You can see I mention leakage and have a table showing lower-risk and higher-risk types of offsets. I also call out a few of the studies you refer to in footnote 10. But, yeah, it's a lot to cover, and I may not have highlighted the risks enough. Maybe I'll do a follow-up at some point. In the meantime, please feel free to share any references you particularly like so people can take a look. I appreciate your bringing this up and emphasizing it.

@Anon: As far as I know, there are no guarantees around offsets, though maybe climeworks comes close. Even if a region has stable enough leadership, laws, and incentives to protect a forest for 50-100 years, another country nearby may start taking down even more trees as demand for timber (or farmed shrimp) moves over there. These issues are pretty tricky, as they are very intertwined with economics and trade. I watched a video recently of Eric Lambin, an expert on land-use who is part-time at Stanford, talking about this. You could start at 9:15 where he talks about Costa Rica. There are also more favorable examples, like Bhutan, which protected its forests and then imported from India, whose farmed timber has much lower impact.

This is why reducing demand is preferable, because it is lower risk.

On mangroves, you might be able to find some good leads here. Atmosfair does have a project that helps conserve mangroves, but they aggregate all of their offsets so you can't just pick and choose that one. Feel free to share what you find!


 +   8 people like this
Posted by No Solution At Present, a resident of Barron Park,
on Feb 26, 2020 at 8:55 am

To realistically address & resolve your issue will require a significant reduction in business, vacation & immigration related air travel...and that's nowhere on the immediate horizon.

Increasing ridership on planes by decreasing seating space will also make flying an even crappier experience than it is today.

The only way to alleviate this problem would be to bring back helium-filled blimps or dirigibles with jet boosters that could be fired-off periodically to increase crusing speed.


 +   1 person likes this
Posted by Sherry Listgarten, a Palo Alto Online blogger,
on Feb 26, 2020 at 12:01 pm

Sherry Listgarten is a registered user.

@No: Do you want to clarify what you mean by "immigration related air travel", and why you think that is a significant component of aviation?


 +   1 person likes this
Posted by Anon, a resident of Another Palo Alto neighborhood,
on Feb 26, 2020 at 2:28 pm

Posted by Sherry Listgarten, a Palo Alto Online blogger,

>> @No: Do you want to clarify what you mean by "immigration related air travel", and why you think that is a significant component of aviation?

I have "friends and relations" who immigrated here from the East Coast, and, they constantly fly back and forth to see each other. Yes, they Facetime and Skype and etc. *also*. I would take "immigration-related" to be synonymous with "family-related" in this context.



 +   2 people like this
Posted by No Solution At Present, a resident of Barron Park,
on Feb 26, 2020 at 3:33 pm

>>> @No: Do you want to clarify what you mean by "immigration related air travel", and why you think that is a significant component of aviation?

[Racist comment removed. It asserted broad, derogatory generalizations about a few countries and the behavior of people from those countries.]


 +   3 people like this
Posted by What's my line?, a resident of Adobe-Meadow,
on Feb 26, 2020 at 5:56 pm

He's baaaaaaack!

;-)


Thank you for removing his racist comments. One wonders what he thinks when one of Trump's own handlers (Chief of Staff Mick Mulvaney) said out loud this week:

“We are desperate"desperate"for more people. We are running out of people to fuel the economic growth that we've had in our nation over the last four years. We need more immigrants."


Thanks for the answer on the coal. Sigh - how depressing!


 +   4 people like this
Posted by Technically, a resident of Adobe-Meadow,
on Feb 27, 2020 at 12:03 am

Unfortunately, even if all us privileged 1st world elites sat on our hands in the dark with the heat off tearing our self woven from recyclable material shirts in penance, it wouldn't make a hill of beans difference. The Chinese and Indians simply refuse to live in abject poverty anymore. The world needs a technical solution, not convincing educated wealthy people to take their one and only life in which they came out on top and live like feral dogs.

One great tech solution hs been fracking. Surprise -- it's the thing that really moved the needle to lower US carbon intensity, but w/o China coming along for the ride it will only help a bit. But, it could be a great transitional solution. Solar is fine, but we probably need next-gen modular nuclear reactors or ... maybe Fusion will come through. With cheap green energy, we can live well and scrub carbon directly from the sky. Problem solved. And/or we'll need to dabble a bit in geo-engineering. Welcome to the new world.

We're a technical artifact producing species. We need a technical solution. If we go "back to nature", it won't support nearly all of us and we'll be denying the core aspect of being human.


 +   2 people like this
Posted by What's my line?, a resident of Adobe-Meadow,
on Feb 27, 2020 at 6:41 am

"but we probably need next-gen modular nuclear reactors"

[Portion removed: disparaging (see guidelines). The commenter is pushing back against nuclear (expensive) and fusion specifically (has been promising for a long time), is emphasizing the need for storage with solar/wind, and is generally arguing against "magical" thinking.]


 +   3 people like this
Posted by What's my line?, a resident of Adobe-Meadow,
on Feb 27, 2020 at 6:45 am

The "why bother, cuz other countries" form of denial is pernicious.

That said... y'all have a great day! It's gonna be gorgeous out there. Short term - pray for rain!


 +   4 people like this
Posted by Sociology Is Not A Science, a resident of Crescent Park,
on Feb 27, 2020 at 2:41 pm

>> The Chinese and Indians simply refuse to live in abject poverty anymore.

^^^ But only the wealthy and/or highly educated Chinese and Indians actually escape the bonds of poverty.


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