Carbon Calculating: Understanding Your Airline Travel Impact
Reducing travel for business and family visits is one of the most impactful choices we can make to reduce our climate impact. When we travel, we should make it count, but we can’t do that unless we understand the consequences for the environment. In this installment of our Carbon Calculating series, discover how to calculate your carbon emissions for air travel, and which carbon calculator services provide the most accurate results so you can make informed choices.
The modern habit of jumping on a plane to meet with a client for an hour or two, to spend time with family, or just to get away for a break contributes heavily to most Americans’ carbon footprint. Air travel accounts for 3.5% of effective radiative forcing impacts from human activity — global warming — and 2.5% of annual global CO2 equivalent emissions, according to Our World In Data. In addition to carbon dioxide, aircraft vapor trails and nitrogen oxide emissions contribute to a higher impact per mile than traveling at sea level. A single roundtrip cross-country flight from Seattle to Washington, D.C. produces about 1,155 pounds of CO2 per passenger, equal to the average human’s emissions for an entire month of living.
Earth911 tested calculators using premium economy seating for two round trips between Seattle and each of the following: Washington, D.C., Los Angeles, and Amsterdam, for a total of 32,532 miles of flying. This is about 1.5 times the average miles flown by airline mileage club members, according to a pre-pandemic 2018 report by IdeaWorksCompany and CarTrawler.
As we found with energy emissions estimates generated by a variety of carbon calculators, air travel carbon footprint data varies by orders of magnitude, depending on which tool you use. In a test of six flight emissions calculators using the same trip data, we received estimates that ranged from 4,101 pounds of airline travel emissions per year up to 27,790 pounds. Our DIY estimate of 14,314 pounds of CO2 emissions for our premium economy flights, which we will explain below, fell in the middle of the range.
If Only Airline Footprints Were Easy To Calculate
Air travel carbon footprinting is guesswork because many factors can change the actual emissions during a flight. The many variables include, but are not limited to, the type of aircraft and class of seating you choose, the weight of your luggage, how the plane was fueled, how crowded the plane is, and the weather on the day you fly. There is no way to accurately measure your airline footprint using the information provided by an airline, so we must be satisfied with estimates until airlines start reporting footprints to passengers.
For example, IBM offers this formula for calculating carbon emissions generated by a flight, with the data that cannot be found by a passenger in bold:
CO2 = ((Distance Traveled + Fuel Usage) * (Emission Factor * Heating Value) * Density)
Without knowing the amount of fuel used, the heating value (the heat generated by the specific fuel used), and the density (the percentage of seats filled), we cannot find our footprint. But IBM misses other factors, such as the class of seating you occupy on the flight. First and business class seats take more space, and so require more fuel to lift and move than premium economy seats, which require less fuel. If you are flying into a headwind, the plane will be in the air longer and burn more fuel, and if you have stops in your itinerary, the added take-offs and landings can increase the carbon emissions by about 12%.
The DIY Way
Notice that “emissions factor,” the amount of CO2 emitted per mile per seat in each class, is available. But this, too, is a matter of estimating rather than exactly measuring your CO2 emissions for many of the same reasons cited above. A more heavily loaded plane, due to more passengers bringing more luggage, changes the performance of the plane and resulting emissions.
The International Air Transport Association (IATA) offers a technical description of emissions factors that can’t be easily translated for passenger use — the airlines don’t provide all the necessary information. So, we developed the following list of emissions factors based on The Carbon Fund’s estimate that an economy-class seat is responsible for 0.2 kilograms (0.44 pounds) of CO2, and increased each seating class’s emission factor by the same percentage as the average increase in legroom in the large seats.
With this information, you can add up your total miles flown for the year and use this easy formula to estimate your travel-related carbon emissions:
Total CO2 emissions from flying = YOUR ANNUAL MILES FLOWN * EMISSION FACTOR FOR YOUR SEATING
If you fly in different seating classes, break out the miles flown by class, performing the calculation for each, and add up the total CO2 emissions. While still a rough estimate, simply multiplying the number of miles you fly by the emissions factor for your seat provides an aggressive estimate for your use when deciding whether a trip is worthwhile.
Based on these factors, flying 3,000 miles in economy class will produce:
- 1,320 pounds of CO2 in economy class,
- 1,650 pounds in premium economy,
- 3,870 pounds in business class, and
- a whopping 6,300 pounds of atmosphere-warming greenhouse gases in first class.
Makes you think, doesn’t it? Cutting air travel can lead to a huge change on your annual lifestyle impact on the environment.
Should Air Travel Be Offset?
Many airlines and carbon calculator providers encourage people to offset their airline emissions. The idea is that paying to remove CO2, by using technology, planting trees, or through other programs that help avoid emissions, will wipe away the carbon cost of our travel. Nevertheless, your flight did emit the CO2, which remains in the skies. We discourage you from thinking carbon offsets make your travel impact-free.
Carbon credits will play an important role in creating economic incentives that encourage decarbonization, but they should not be treated as a salve for a guilty conscious. Even if you do buy carbon offsets, those programs don’t deliver immediately, so your flight’s emissions will warm the atmosphere while the impact of the offset is realized at some future date. Another approach is to consider how you might pay the social cost of your flight’s carbon emissions.
Traveling less frequently and only when in-person will do will make a big difference in your contribution to ending global warming. Yes, do go see your grandmother, but maybe you could skip the two business trips to attend short meetings. Or try to combine trade show trips with business trips to reduce your 0verall need to travel.
And ask your airline for low-carbon flight options. Airlines can’t deliver much today, but let them know you will be making future travel decisions based on their improved environmental performance. For instance, more sustainable, but not carbon-neutral, aviation fuels are on the horizon.
Grading the Flight Carbon Calculators
Google Flights Carbon Estimator
Grades
Travel estimate: A+
Total footprint estimate: N/A
The Google Flights search tool uses European Environmental Agency emissions estimates to provide an CO2 footprint for each flight option it presents. The data is also based on the seating class selected and other factors that include the type of aircraft and route flown, which we think produced the most accurate results of any of the calculators we reviewed. Each leg of a flight clearly reflects the different planes, typical weather, and outes involved. For example the emissions impact of outbound and return flights involving the same city vary by the time of day. If you’re planning a trip, visit Google to find your flight and check its estimated emissions; the tool also helps identify lower-carbon flight options.
Conservation International Flight Calculator
Grades
Travel estimate: C+
Total footprint estimate: N/A
Not all carbon credit vendors over-estimate travel impacts, and Conservation International’s flight-only calculator delivered a surprisingly low estimated impact at 7,140 pounds of CO2 for the six flights we entered. It also lets users enter total mileage and calculate the impact with one click, which yielded 10,670 pounds, which we believe is close to the correct estimate. Conservation International does not capture flight details, such as the type of plane or seating class; if it assumes you are flying in economy class, that may account for the lower reported impact when the flights were entered separately.
World Land Trust Carbon Calculator
Grades
Travel estimate: B+
Total footprint estimate: C-
Like Google, the World Land Trust Flights Carbon Calculator factors seating class into emissions estimates, and it also offers an easy way to enter multiple trips to simplify finding an annual total. While the total emissions for our six flights came in 25% higher than Google, this tool appears to be among the most accurate, because it is A carbon credit vendor, pricing for offsets was slightly higher than others we were offered on competing sites. Unfortunately, the lifestyle calculator covers on air travel, driving and household impacts in any detail.
Guardian Flight Calculator
Grades
Travel estimate: C-
Total footprint estimate: N/A
The Guardian, a British newspaper that has been on the forefront of climate reporting, provided a flight calculator as part of an article about the environmental impact of travel. We found the total estimated footprint of our six trips to be surprisingly low at only 8,364 pounds, but the report it accompanied is well worth a visit.
MyClimate Flight Calculator
Grades
Travel estimate: B+
Total footprint estimate: N/A
MyClimate’s flight calculator, another carbon offset provider, delivered a very reliable result, in line with our own and two other calculations. Then, it asks visitors to pay rather than offering tips for reducing travel impacts. More insight would be helpful, though we found their many different emissions calculators, including for cruises, events and companies, very useful.
International Air Transport Association Flight Calculator
Grades
Travel estimate: F
Total footprint estimate: N/A
The airline industry’s emissions tool came in at the bottom of our rankings, earning an “F” because, of all the organizations reviewed, it should have access to all the relevant information necessary to provide an accurate estimate of air travel impacts. Nevertheless, it asked for more information than most of the other calculators, including seating class and type of airplane. Yet the IATA reported only 4,742 pounds of emissions for our sample trips, less than a third of the average estimate across all the other calculators.
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