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A New Shade of Green

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 much is enough? It's personal.

Uploaded: Feb 16, 2020
I expect many of you don’t want to read more about how flying hurts our climate. Our list of “things that are bad” is already long enough. And if the environmental movement becomes the “Thou Shalt Not” movement, it is doomed.

But I hope you will bear with me. Maybe you’ll find some low-hanging fruit, or be motivated to support relevant policies at work or in government. Flying is a growing source of emissions globally and a surprisingly large source for many of us personally. On the global front, you may have heard that aviation represented 2.4% of global CO2 emissions in 2018. That is a 32% increase over the past five years. You may also have heard that aviation emissions are projected to triple by 2050, which means they are on track to be 25% of global emissions in thirty years if countries meet their Paris agreements. But you may not have heard that the recent annual growth rate of 5.7% is 70% higher than was assumed for those projections. And none of these forecasts includes the non-CO2 impact of aviation (e.g., increased contrail cirrus and nitrogen oxides), which by most estimates is comparable to the effect of aviation’s CO2 emissions on global warming. (1)

So, flying has a big impact on climate and it’s getting bigger. Furthermore, the aviation impact from our wealthy area, where flying is more common, is particularly large. Consider these common sources of our own CO2 emissions (values are approximate):

- Driving: 6 tons/year. This applies to someone driving a 25mpg gas-powered car for about 15,000 miles. (2)

- Home heating: 3 tons/year. This assumes 500-600 therms is used for space heating and water heating, which is ballpark for a house in our area. (3)

- Diet: 2.5 tons/year. This is for an average American diet. (4)

And then consider the impact associated with these common flights from SFO. These are approximate CO2 emissions for each economy-class passenger. (5)

- Round-trip SFO to Honolulu: 1 ton
- Round-trip SFO to Boston: 1.5 tons
- Round-trip SFO to London: 3 tons
- Round-trip SFO to Hong Kong: 4 tons
- Round-trip SFO to New Delhi: 4.5 tons

How does your flying add up?

Another way to look at this is to consider things you might do to reduce your emissions, and then compare that with the option of flying less.

- Go vegan: 1 ton/year. If you opt to go vegan for one year, you would save about 1 ton of emissions compared to the average American diet. (4) That is about the same as a round-trip to Honolulu or Atlanta.

- Bike to work: 1.5 tons/year. If you commute by bike 230 days of the year instead of driving your 25 mpg car the 8 miles each way, you would save about 1.5 tons. (2) Or you could save the same amount by omitting one round-trip flight to Boston.

- Freeze: 3 tons/year. You would save a substantial 3 tons of emissions by using only cold water and no heat. Or you could stay warm and forego a trip to Europe. (3)

That is a silly comparison, but the point is that the impact of our flying is substantial, particularly for the longer (and higher) flights. Skipping one trip to New York makes a bigger difference than going vegan for an entire year. Flying to Boston undoes all the climate benefit of biking to work for a year. Just one trip to London has as much impact as operating both your gas furnace and water heater for an entire year. That trip to Asia? The same as eight months of driving.

I was surprised by this. Flights don’t take that long, so it didn’t occur to me they would do so much damage. The bad news is, I have flown a lot, especially over the past ten years. The good news is, there are lots of ways for me to fly less. Here is a list of where I have gone over the last decade or so, not including a few business trips:

- Minneapolis, Los Angeles, and San Diego (3-4 times each)
- Costa Rica (three times)
- Hawaii (two times)
- Maine, Massachusetts, Washington, Alaska, London, Tanzania, Nepal (once each)

Yikes. That amounts to one longer trip and one or two shorter trips every year. Were these trips worth it? Some I would absolutely do again -- visits to family in Minneapolis, two wonderful stays in Costa Rica, a trip to Disneyland, a visit out east, maybe one of the overseas trips. But we could easily have halved our flight mileage and been just as happy with our vacations. A great vacation for me involves some combination of relaxation and discovery, and in my experience you can find those pretty independent of distance.

People sometimes talk about mindful eating, and what I’ve started thinking about is mindful flying. By paying attention to how much I am flying and spreading it out, I hope to value it more. I also want to be more creative with closer-to-home vacations, though I could use some help with that. (It seems like there is a lot of potential there.) I am positive I can substantially reduce my flying while still loving the vacations and broadening my horizons.

That said, I know I will continue to fly some, and I imagine many of you will as well. So in the next post I will share some practical tips on selecting and offsetting those flights you do choose to take. For this week, I’m interested to hear your thoughts on scaling back on flying -- is it something you would consider? -- and also what your best local-ish vacations have been. I’d also love to hear if your workplace is cutting back on flights and how that’s going.

Notes and References
0. The first post in this series on flying can be found here.

1. This recent report from the International Council on Clean Transportation is a great overview of aviation emissions.

2. A car creates about 20 pounds of carbon dioxide for each gallon of gas it uses.

3. PG&E cites its emissions rate for natural gas at 13.446 pounds of CO2 per therm. I don’t know if that includes processing and distribution leaks. (Update: A commenter (see below) shows that the PG&E estimate does not include the distribution leaks, which would approximately double the heating emissions. The fuel-distribution emissions are not included for the driving or flying estimates. He estimates flying would increase by 15%. Not sure about driving.)

4. I used this information on diet, but I have seen a wide range of estimates.

5. I will go into more detail on where these estimates come from in the next post. But a quick summary would be to take the airline estimates for CO2 emissions (e.g., United or Delta) and double them to account for emissions from non-CO2 climate impacts such as contrail cirrus and nitrogen oxides.

Current Climate Data (January 2020)

Temperature change for January 2020 compared to 1981-2010. You can see that we experienced the temperature change much less than other parts of the US.

Global impacts, US impacts, CO2 metric, Climate dashboard (updated annually)

Comment Guidelines
I hope that your contributions will be an important part of this blog. To keep the discussion productive, please adhere to these guidelines, or your comment may be moderated:
- Avoid disrespectful, disparaging, snide, angry, or ad hominem comments.
- Stay fact-based and refer to reputable sources.
- Stay on topic.
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What is it worth to you?


Posted by Tom, a resident of Menlo Park,
on Feb 16, 2020 at 11:18 am

Thanks for the great post to get us looking at actions and activities.

I continue to advise that we include full GHG impacts (upstream and downstream) in our individual decision analysis (and policy analysis) so we can see the benefits of our savings in CO2 equivalents ( CO2e ).
The idea is to include the emissions of tailpipe (even a jet tail pipe at about 21.1 lb. CO2 formed per gal of jet fuel burnt in engine Web Link )
and its downstream emissions (e.g. cirrus and nitrous CO2e are about as large a warming impact as jet tailpipe CO2)
and its upstream emissions (from mining, processing, refining and transporting typically: 30% again as big as the tailpipe from fossil fuels). This leaves jet fuel at 48.5 lb. CO2e/gal (21.1 * 2 + 21.1 * 0.3 =2.3 times combustion emissions )
In the case of methane we definitely need to include its fugitive emission that are themselves larger than the tailpipe combustion emissions ( CH4 CO2e from fugitive = 3.6% leakage * 84 GWP * 16/44 * = 1.1 times as much warming as the combustion emissions ). Leakage estimates come from this paper on the future of natural Gas Web Link
The 84 GWP is the important 20 year value Web Link and 16/44 is the molecular weight ratio of CH4 = 16 / CO2 = 44
I think the 13.4 lb./therm number from PG&E ignores fugitive leaks and counts processing and shrinkage combustion consumption amounting to 1.7 lb. CO2 combustion emissions needed to process and ship a therm to us.
PG&E did count it taking 1.15 therms of gas extracted to deliver one therm to the home. (13.4/11.7) 0.15 therm is burnt before the home and 1 therm is burnt in the home and 0.036 therms are leaked. My need for one therm to burn causes 26.3 lb. CO2e ( 11.7 tailpipe CO2, 1.7 upstream tailpipe CO2 and 12.9 lb. fugitive CO2e )
So electrifying the home (with clean electricity) to eliminate 500 therms of home gas burning would save 13,150 lb./year CO2e ( 6.5 tons/yr ).
Hopefully this simplification of including the upstream and downstream impacts from decisions will avoid "number storms" where all kinds of numbers fly around because folks are randomly excluding one or two or 3 significant impacts.)
When I ride my bike I save about 28 lb. CO2e/gallon gasoline.
When I reduce flights I save 48.5 lb. CO2e/gallon jet fuel.
When I electrify my home I save 26.3 lb. CO2e/therm of methane. (or you can "freeze" and do the same.)

Posted by neighbor, a resident of Midtown,
on Feb 17, 2020 at 11:00 am

Thank you Sherry and Tom.

In order to engage in mindful eating/flying/etc. - can we say mindful polluting? - wouldn't we benefit from some data about the real-world consequences? In other words, how many tons does it take to create a death, or extreme suffering?

In George Marshall's book, carbon detox (2007, Gaia/Octopus) he writes about a speculative "emissions-death ratio" (pg. 25) as suggested by Craig Simmons of the UK, "one person could die, be made homeless...or face starvation for every 102 tonnes of carbon dioxide we add to the air."

That's in addition to the millions of deaths per year due to "local" air pollution:

More recent information can be found at:
"Currently, the US experiences about 200,000 early deaths each year due to emissions..."
Web Link

{Australian} "Professor Steve Keen...shows that 4°C of warming would mean that approximately 6.7 billion people die"
Web Link

Do you know of any other attempts to come up with an emissions-death ratio besides what's in the G. Marshall book?

Thank you again, Neighbor.

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Feb 17, 2020 at 4:00 pm

Sherry Listgarten is a registered user.

@Tom. Thanks for the calculations. It sounds like you would double the estimate for home heating from 3 to 6 and you would increase the flight emissions by 15%. What about driving, which also does not include the upstream or downstream effects (gas distribution, soot, etc)? Or the typical diet? I used *very* rounded numbers in part because of the variabilities in estimating these, but am happy to adjust for gross inaccuracies. I mainly want the relative values to be approximately correct.

Regarding methane leaks, I agree on using the 84x multiplier, but what I haven't been able to get a good read on is how quickly PG&E is addressing these leaks. I understand they have much better tech deployed now for identifying them, but what I don't know is how hard they are to fix. There's a big doc here, but I haven't waded through it.

BTW, I wrote this post initially using heat pumps and EVs as examples, but they aren't really comparable to skipping a plane flight because they are a permanent fix, whereas you have to skip a plane flight each year. So that's why I said "freeze" (or the milder "turn down your thermostat") rather than "heat pump", and "bike" rather than "EV", though the others are often better options for people.

Anyway, I'm happy to make adjustments as long as the relative values are about right (rounded to the nearest half-ton, which is a big round).

@neighbor. I haven't, and I would expect there are far too many variables to give a meaningful estimate. I see things more along the lines of how many people would have to move. But disease, wars, food and water shortages -- so many problems. A report like this is even too much for me to read. I like to keep focused on positive actions we can take. On that note, I was very happy to see Bezos devoting $10B to climate change. I look forward to our government's catching up. I heard some policy people remark that mitigation (reducing/capturing emissions) is much cheaper than resiliency (dealing with the consequences of high emissions), so I hope that will encourage our policy makers to act sooner rather than later.

Posted by Linda, a resident of Menlo Park: Fair Oaks,
on Feb 17, 2020 at 7:29 pm

My husband and I lived in Palo Alto Menlo Park for 40 years. We did not use a furnace or heat elements overnight while we were sleeping. I used a down blanket and kept a light coat nearby in case I needed to get up during the night. For us this was way more comfortable and pleasant than having a furnace on overnight. I hope more people can consider doing this. We even kept a window partly open during during the night.

Posted by Robert Neff , a resident of South of Midtown,
on Feb 17, 2020 at 7:40 pm

Robert Neff is a registered user.

Great post.

Posted by Local, a resident of Barron Park,
on Feb 18, 2020 at 10:46 pm

Great post - super interesting and never knew. I am a bike commuter, mostly veggie, endlessly turning off lights and down our heat but fly a lot. Turns out flying totally kills all the other savings - i never knew and will try to change.

Posted by Harvey, a resident of Barron Park,
on Feb 18, 2020 at 10:52 pm

After reading this article I was curious whether when taking a trip of a few hundred miles (e.g. Bay Area to Los Angeles) whether driving or flying would result in lower CO2 emissions.

I found an article at Web Link that says:

"It's a complicated comparison

In general ... driving generates less greenhouse-gas emissions than flying; and ... domestic airliners are less fuel efficient than cars. But there are lots of factors that go into determining a transportation mode's environmental impact �" such as the distance traveled, the number of passengers and the vehicle and fuel types."


“from a carbon perspective, motor coaches and trains are among your lowest-emission options, especially on shorter (less than 500-mile) trips."

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Feb 19, 2020 at 9:12 pm

Sherry Listgarten is a registered user.

@Harvey -- Thanks, great info! BTW, one thing I learned when reading for this post was that SFO-LAX is the most popular flight route in the entire country!

As you suggest, driving alone is not a good option either, though carpools are okay. The best bet is the bus. I wrote a post about that earlier, if you are interested. I'm not as sure about trains (like the Amtrak Coast Starlight), since they are not especially high capacity and they often don't go a very direct route.

My 2c: This flight route is short enough that if you do it a few times, it's okay. And it's easy enough to drive if you're going with family or friends. But if it's something you need to do often on your own, that's tougher...

Posted by MACA, a resident of Menlo Park: Fair Oaks,
on Feb 20, 2020 at 8:59 am

What about naturally occuring events like the wildfire in Australia that spewed many years worth of CO2(900 tons of CO2) How does the planet/we offset this?

Posted by Oval Balloon Alternative, a resident of College Terrace,
on Feb 20, 2020 at 3:36 pm

Bring back blimps & dirigibles...people are in way too much of a hurry these days.

Helium is safe + residents will no longer be complaining about passenger planes on approach disrupting their exclusive Palo Alto lifestyles.

Posted by musical, a resident of Palo Verde,
on Feb 20, 2020 at 9:11 pm

"How does your flying add up?" Ok, that 737 is going SFO-LAX whether I'm on it or not. I tip the scale at 150 lbs, so boarding the aircraft I increase its weight by about 1/1000 vs an empty seat, increasing the fuel burn by maybe one gallon at most, or 20 pounds of CO2.

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Feb 21, 2020 at 8:19 am

Sherry Listgarten is a registered user.

@MACA: Yeah, it’s maddening isn’t it? As the planet gets warmer there are more fires, which further warms the planet. There are a number of these positive feedbacks (reduced snow/ice cover is another). I was talking to an atmospheric scientist yesterday who was musing about Australia’s horrific fires and wondering just what it will take for people to really care.

@Oval: Super interesting! I’ll be writing about alternative aircraft in a few weeks (though not dirigibles), but your point about not having enough time is a good one to dig into. I wonder sometimes if we all had more time, would we be more conscious of our use of resources?

@musical: Hmm, that surprises me. You’re not a fan of collective action? Do you vote? Save water during droughts? Throw your trash in the right can? Or are those different somehow? There is no doubt that sometimes these voluntary things work and sometimes they don’t. Which do we want it to be?

Posted by Unbelievable, a resident of another community,
on Feb 23, 2020 at 9:36 am

I cannot believe what I imagine is a fairly educated, intelligent group of people are looking at climate data for THIRTY YEARS and seriously holding that up as dire climate change. Have y'all ever heard of WEATHER?

And truly if you're really that concerned about saving the earth you then offer up to graciously cancel ONE of your multiple trips to Costa Rica! Do you not see how ridiculous this is?

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Feb 23, 2020 at 1:17 pm

Sherry Listgarten is a registered user.

@Unbelievable. Your comment is spot on, notwithstanding its hostility. Given we have a very real, significant, and urgent climate problem, it’s clearly not enough that I, or people like me in general, voluntarily reduce our flying by half (as suggested here). What about 75%? Or 90% for the biggest flyers? Think about it in terms of beef consumption, which is a much bigger problem for Americans, with an even larger impact on climate. What if everyone voluntarily offered to eat 50% less beef? And the biggest beef eaters 75%? That would be a start, but it’s still not enough. We’d still eat far more than the rest of the world, and our cattle would still emit far too much methane and take up far too much land that we need for other uses. There are plenty of fine alternatives to flying (vacation closer to home) and to beef (eat beans, or even chicken). Why don’t people step up? Why don’t voluntary actions suffice? Do we need some kind of policy? Should we just make it so expensive that people can’t afford it any more? Or do we ration it, like in wartime? And if we do that, what happens to the cattle farmers? Or the people in the travel industry?

This is not easy. I think that is why so many people just don’t want to believe in global warming, or how big the problem is. But that is incontrovertible. So… what?

Great comment, thank you.

Posted by Unbelievable, a resident of another community,
on Feb 23, 2020 at 2:16 pm

It is not meant to be hostile, it is however incredulous. Again, you've held up 30 years of data and now that's very “real, significant and urgent"? It's like Chicken Little, not satisfied unless the sky is falling and everything's collapsing. Remember the oZone layer. Didn't happen. And these outrageous claims of “climate change and end of world" isn't happening either, check back in 30 years and we'll chat.

Now, a reality I am completely on board with is reducing trash. We need to stop producing so many throw-always, plastics, items that take up our space in Landfills. THAT would be a cause much more worth fighting for.

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Feb 24, 2020 at 9:50 am

Sherry Listgarten is a registered user.

Yeah, I don't spend much time in this blog on the basics of global warming. I do have two posts on the science, plus this one on how two degrees can make such a difference. A good resource for the basics, though, is Katherine Hayhoe's YouTube channel. And, yes, if we could have as effective a global agreement for climate change as the Montreal Protocol was for ozone, it would be terrific.

As you say, it is crazy how much pollution we create, not just in the atmosphere, but on land as well. How do we create incentives for manufacturers to do things differently, and for people to do things differently? Is your community doing anything? It'd be great if you want to share that.

Posted by shukaduka, a resident of Old Palo Alto,
on Feb 25, 2020 at 10:09 pm

One of the fears I have is that for some reason this blog will cease. It shows what diligent research and direct messaging is, challenging us all to learn how better to do these skills and be citizens of the planet. Contrast with the slick videos produced for candidates! Also, the responses, especially the yucky ones, help me understand the world we live in. I keep telling people to tune in to this blog. Thanks!

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Feb 26, 2020 at 4:46 pm

Sherry Listgarten is a registered user.

@shuka. I am learning a lot, too -- we are all in this together. Like you, I particularly appreciate everyone sharing their thoughts and comments.

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