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By Sherry Listgarten

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)

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