Abstract

The Aspiration personal carbon footprint calculation represents a statistically average U.S. individual's climate impact over a defined period (typically one year) including both the direct greenhouse gas (GHG) emissions generated by the individual’s lifestyle as well as the indirect GHG emissions generated through their finances such as banking and investing. This is a data-driven, science-based approach developed in alignment with the Greenhouse Gas Protocol GHG accounting recommendations and tailored to GHG accounting for individuals. This calculation provides individuals with an understanding of how their current behaviors impact the climate, helps them identify their largest areas of opportunity for improvement, and acts as a first step to taking climate action. 

Figure A.1 shows a few of the biggest actions a consumer can take to reduce their personal carbon footprint, based on the data and calculations described herein. It is clear that reducing an individual’s indirect emissions of their investments and banking preferences can be one of the more significant ways they take climate action. Simply changing their bank can do more than any of the most common actions like moving to an electric vehicle or installing home solar. 

Figure A.1. Comparison of the climate actions an individual can take and their impact on reducing the individual's personal carbon footprint. 

Introduction

The Aspiration personal carbon footprint calculation models an individual’s climate impact across five high-level categories: 

• Transportation

• Home

• Goods and Services

• Food

• Financed Emissions

Broadly, these categories represent the various lifestyle modalities that impact an individual’s total climate impact. The first four categories represent direct emissions generated from consumption activities, while the fifth represents the indirect emissions from the individual’s savings or investments. 

While the GHG emissions are generated directly due to the individual’s behaviors, the responsibility to reduce and mitigate the emissions is not solely on the individual. There are systemic, cultural, and infrastructural challenges that inhibit individual’s from living a completely GHG emission-free lifestyle, and organizations including companies and governments have a significant responsibility to decrease emissions directly or through policy. However, individuals have the right to understand how their behavior drives GHG emissions, take action to reduce their emissions, and mitigate those remaining emissions, if they so choose. 

The remainder of this methodology paper is structured to discuss the GHG accounting methods and data used in the Aspiration personal carbon footprint calculation for each of the categories listed. 

Transportation

Mobility is a key indicator of prosperity in a country and individual’s life. However, currently most modes of transportation (e.g., vehicle travel, flights) require fossil fuels to power them. There are two general approaches to estimating the greenhouse gas (GHG) emissions associated with personal transportation: fuel based methodology and distance based methodologies. 

Fuel based methodologies are the preferred and most accurate GHG estimate methodology. However, fuel consumption data is not typically readily available or known which makes it difficult to apply this approach for individuals. 

The distance based methodology is marginally less accurate than fuel based approaches (if accurate fuel consumption data is available), but has the advantage of using more readily available or known data from the individual. Additionally, this approach can more easily be used in planning or scenario analysis as individuals are more likely to know how much transportation distance they could reduce via driving less or taking fewer flights. 

Thus, for transportation, the Aspiration personal carbon footprint calculation uses a distance-based GHG accounting approach rather than a fuel-based quantification method. Transportation includes personal vehicles, public transportation, and air transportation.

Personal Vehicle Transportation

Calculation Methods

Vehicle use GHG emissions are calculated in two segments: the emissions generated during the year of vehicle use and the emissions generated from manufacturing the vehicle. The GHG emissions of each segment is summed to obtain the total emissions per year of the vehicle. It is assumed that an individual only has one vehicle for the purposes of this calculation.

Vehicle Use: 

Energy Used (gge/year) = Distance (miles/year) / fuel economy (mile/gge)

GHG Emissions (kgCO2e/year) = Energy Used (gge/year) x Fuel Emission Factor (kgCO2e/gge)

Vehicle Manufacturing:

GHG Emissions (kgCO2e/year) = Distance (miles/year) x Vehicle Manufacturing Emissions (kgCO2e/mile)

Calculation Data

Fuel economy: The fuel economy data for conventional (internal combustion engine) vehicles is estimated to be 24.2 MPG based on the U.S. Department of Energy’s (DOE) Alternative Fuel Data Center (AFDC) and represents the average U.S. on-road vehicle fleet (AFDC 2020). The fuel economy values of a battery electric powertrain is 85.04 MPGGE based on the Burnham et al. (2021) rather than AFDC data as these vehicles are likely newer and on-road vehicle fleet averages are not available and less representative. 

Fuel Emission Factors: For the internal combustion engine vehicle, gasoline is assumed to be the primary fuel for U.S. consumers. The gasoline emission factor of 8.78 kgCO2e/GGE is from the U.S. Environmental Protection Agency (EPA) (U.S. EPA 2022). For the electric vehicle, typical grid electricity is assumed. Based on the U.S. Energy Information Agency (EIA) data for 2022, the typical U.S. grid electricity carbon intensity is 0.420 kgCO2e/kWh (U.S. EIA 2023). For the electric vehicle plus solar scenario, a solar electricity emission factor of 0.043 kgCO2e/kWh was used based on harmonized lifecycle assessment data from the National Renewable Energy Laboratory (Nicholson and Heath 2021).

Average Vehicle Miles Traveled: The average vehicle miles traveled (VMT) each year is usually specific to each vehicle class. For cars, SUVs, and pickups in the U.S., the yearly VMT is based on the average mileage for the first 13 years of the vehicle’s life which accounts for the majority of the vehicles in the U.S. market and the typical lifetime vehicle miles traveled by the vehicle (Davis and Boundy 2021; Wang et al. 2021). Then, we can use Burnham et al. (2021) to decompose this by vehicle type and estimate that the average miles for a typical car is ~13,000. This calculation assumes that both the electric vehicle and the conventional vehicle are driven the same amount per year.

Manufacturing Emissions: Manufacturing the vehicle components and assembling the vehicle in a manufacturing plant both generate GHG emissions due to the energy (electricity, fuel) and inputs needed to create the components and power the manufacturing facility. These emissions are accounted for by estimating the total emissions generated from the manufacturing process and normalized over the lifetime miles of the vehicle. The total manufacturing emissions generated is a function of the vehicle type (car, SUV, pickup) and powertrain technology (internal combustion, hybrid, etc.) based on the Argonne National Laboratory GREET model. The manufacturing emissions are then amortized over the estimated lifetime miles from GREET based on that vehicle type (Wang et al. 2021). For a typical car with a gasoline internal combustion engine, this comes out to 0.0429 kgCO2e/mi. The same approach is used for a typical electric vehicle which results in a normalized embodied emissions of 0.0627 kgCO2e/mi. 

Results

Based on the data and calculation framework listed above, the total annual CO2e emissions generated by a conventional vehicle and a battery electric vehicle are approximately 5,200 kgCO2e/year and 3,000 kgCO2e/year, respectively. 

Public Transportation

Calculation Methods

Public transit and rideshare/taxi use GHG emissions are calculated according to the formula: 

Miles Traveled (miles) = Number of Trips (trips) x Average Trip Distance (miles/trip)

GHG Emissions (kgCO2e) = Miles Traveled (miles) x Emission Factor (kgCO2e/passenger-mile)

Calculation Data

Average Trip Types: Per the 2017 NHTS data based on households, public transportation trips vary widely across households and are not frequently used (FHWA and ORNL 2020). For the purposes of this calculation, it is assumed that only one rideshare/taxi trip per month is used. Bus, rail, and subway trips are excluded in the current version but could be added in future calculations. 

Emission Factors: The rideshare/taxi emission factors are based on the average car fuel economy with gasoline as the fuel, as described in the “Personal Transportation” subsection above.

Average Trip Length: Average trip length for rideshare/taxi trips is 10.8 miles based on the 2017 NHTS (FHWA and ORNL 2020) summarized in the Transportation Energy Databook (Davis and Boundy 2021). 

Results

Based on the data and calculation framework listed above, the total annual CO2e emissions generated by rideshare/taxi trips for the average U.S. individual are approximately 47 kgCO2e/year. 

Air Transportation

Calculation Methods

Air transportation GHG emissions are calculated according to the formula: 

Miles Traveled (miles) = Number of Flights (flights) x Average Flight Distance (miles/flight)

GHG Emissions (kgCO2e) = Miles Traveled (miles) x Emission Factor (kgCO2e/passenger-mile)

Calculation Data

Emission Factors: Flight emission factors depend on both flight type (short-, medium-, and long-haul) as well as seat class (economy, economy plus, business, first). The flight/seat emission factor combinations are based on the UK Government’s GHG reporting conversion factors database (UK Government 2022). These emission factors align closely (within 0.5%) of the U.S. EPA average flight emission factors but provide additional resolution on seat-type which provides more accurate GHG emission allocation (U.S. EPA 2022). For this calculation, medium-haul flight types are assumed and with a seat class of “average” (reflecting a representative seat class across all flights (UK Government 2022)), resulting in an emission factor of 0.131 kgCO2e/pmt (passenger-mile-traveled). 

The baseline emission factors do not account for radiative forcing¹ and thus are increased by a factor of 1.85 to account for the indirect effects of non-CO2 emissions in line with the UK Government recommendations. While there is uncertainty around the magnitude of the indirect effect of non-CO2 emissions, including radiative forcing is included in the GHG footprint calculations to be more conservative and attempt to capture these indirect effects (UK Government 2022).

Average Trip Length: The average one-way medium-haul flight distance is based on a TEDB summary of NHTS data which aligns well with Schäfer et al. which evaluated short- and long-haul flights (FHWA and ORNL 2020; Davis and Boundy 2021; Schäfer et al. 2019). That distance is reported in nautical miles and is converted to conventional miles by multiplying by 1.151. While the International Civil Aviation Organization recommends a correction distance to accommodate deviations in direct flight path (e.g., stacking, traffic and weather-driven adjustments), the emission factors already account for this and thus direct-distance values are used (ICAO 2018; UK Government 2022). Based on this data, the average one-way flight distance for an average U.S. individual is 830 miles. 

Number of Flights: The average number of flights per year is 2 round-trip flights (4 one-way flights) based on the total passenger miles flown in the US, average flight distance, and total US population (FHWA and ORNL 2020; U.S. Bureau of Labor Statistics 2021). 

Results

Based on the data and calculation framework listed above, the total annual CO2e emissions generated by air transportation for the average U.S. individual are approximately 802 kgCO2e/year. 

Home

Home energy use is a large contributor to an individual’s carbon footprint. GHG emissions are primarily generated from using energy for various purposes including heating, cooling, cooking, lighting, powering appliances, and more. The construction of the home also generates GHG emissions from creating the materials to build the home through the actual construction. Incremental GHG emissions from water usage or waste choices (recycling and composting) are significantly less than the home’s energy usage and not included in this current methodology.

Home Energy Use and Construction

Home energy typically comes from four main fuels: electricity, natural gas, fuel oil, and propane. To estimate the GHG emissions for the home, the average fuel usage is estimated for each fuel source and converted into a GHG emissions estimate. 

Calculation Methods

Home energy GHG emissions are estimated for each energy source (electricity, natural gas, fuel oil, propane) based on the formula:  

Home Use:

GHG Emissions (kgCO2e) = Energy Use (unit) x Emission Factor (kgCO2e/unit)

Home Construction:

GHG Emissions (kgCO2e/year) = 

Home Type Construction Emission Factor (kgCO2e/sqft/year) x Home Size (sq ft)

Calculation Data

Home Energy Mix: The average individual’s home energy mix is assumed to be electricity and natural gas, based on the U.S. EIA’s Residential Energy Consumption Survey (RECS) dataset (EIA 2020).

Home Energy Use: While all homes and occupants are different, the EIA’s Residential Energy Consumption Survey (RECS) dataset was used to estimate the energy consumption of a typical home (EIA 2020). Based on this data, for a typical household that uses electricity and natural gas, the annual electricity usage is around 9120 kWh. Since the EIA RECS dataset is defined at a household level, they are divided by the average household size (2.5 people) to obtain a per-individual electricity consumption value (U.S. Bureau of Labor Statistics 2021). Using the same approach as home electricity usage, the average natural gas usage for a home that uses both electricity and natural gas is estimated to be 57,900 kBTU per year. As with the electricity usage, this value needs to be normalized to a per-individual basis.

Emission Factors: Based on the U.S. EIA data for 2022, the typical U.S. grid electricity carbon intensity is 0.42 kgCO2e/kWh, as used above for the battery electric vehicle (U.S. EIA 2023). The natural gas emission factor is 5.42 kgCO2e per hundred cubic feet (CCF) based on the U.S. EPA’s data for stationary combustion (U.S. EPA 2022). For the home solar scenario, a solar electricity emission factor of 0.043 kgCO2e/kWh was used based on harmonized lifecycle assessment data from the National Renewable Energy Laboratory (Nicholson and Heath 2021).

Construction Emission Factors: The embodied carbon in the home is based on the home type and normalized over the lifetime of the house which is assumed to be 50 years (Jones and Kammen 2014). The total emissions for a home are based on the Embodied Carbon in Construction Calculator (EC3) Tool reference homes and defined at a per square foot level (BuildingTransparency.org 2022). Based on this approach, the average single family home is estimated to have an embodied carbon intensity of 1.148 kgCO2e/sq-ft/year. This estimate is comparable with other EIO-LCA and bottom-up LCA approaches (Wang et al. 2021; Jones and Kammen 2014).

Results

Based on the data and calculation framework listed above, the total annual CO2e emissions generated by the average U.S. individual’s portion of their home are 5,700 kgCO2e/year. 

Goods and Services

Purchased goods and services contribute another major area of GHG emissions for an individual. Emissions in this category are typically embedded in the product or service, rather than the actual good/service creating emissions directly. 

One example of this is purchasing a shirt. It takes materials (e.g., cotton, polyester), water, and electricity (and more) to create a shirt that can be purchased. The GHG emissions generated by producing the materials, water, and electricity that were used to manufacture the shirt need to be accounted for and can be attributed to the individual who purchased the shirt (providing the demand for businesses to identify and fulfill). 

Goods and services are broken down into two segments, hotel stays and other purchases, based on their calculation methodology. 

Accomodations

GHG emissions from hotels are primarily caused by their energy use (e.g., electricity, natural gas) for the rooms along with the other hotels offerings (e.g., pools, gym). 

Calculation Methods

The hotel GHG emissions are estimated based on both the number of nights an individual stays in the hotel and the segment of the hotel that is used:

GHG Emissions (kgCO2e) = Stays (nights/year) x Accomodation Emission Factor (kgCO2e/night)

Calculation Data

Hotel Emission Factor: The emission factors used for the GHG emission calculations are defined at an average country and hotel segment level (Economy and Midscale, Upper Midscale, Upscale, Upper Upscale, Luxury). Economy and midscale hotels are typically those that offer limited facilities/amenities and do not have a full-service restaurant. Upscale, Upper Upscale, and Luxury properties typically have a wide variety of onsite amenities, such as restaurants, meeting spaces, exercise rooms or spas. The emission factors are based on the Cornell Hotel Sustainability Benchmarking Index (Ricaurte and Jagarajan 2021). For the average U.S. individual calculations, an emission factor of 18.6 kgCO2e/night/room was used representing an average across hotel segments for the U.S. 

Hotel Nights: The average individual number of nights in a hotel is 3 per year based on the average U.S. household year expenditure for rented dwellings divided by the average daily rate of hotels (U.S. Bureau of Labor Statistics 2021; Lock 2022).

Results

Based on the data and calculation framework listed above, the total annual CO2e emissions generated by the average U.S. individual’s hotel stays are 56 kgCO2e/year. 

Other Goods and Services

GHG emissions from other goods and services that are used by an individual are based on the amount of money spent on them. 

Calculation Methods

The goods and services GHG emissions are estimated based on the individual’s typical spend across different goods/services categories. The general calculation approach is:

Category Spend ($) = Monthly Category Spend ($/month) x 12 months/year

GHG Emissions (kgCO2e) = Category Spend ($) x Category Emission Factor (kgCO2e/$)

Calculation Data

Category Spend: The average individual’s spend across each category is based on Consumer Expenditure Surveys from the U.S. Bureau of Labor Statistics (BLS) 2020 survey data, normalized per person and adjusted for inflation (U.S. Bureau of Labor Statistics 2021). Categories included in the calculation and spending amounts are shown in Table 1. Note that no pet spending was included in this personal carbon footprint calculation.

Table 1. Average spend data by category used in the personal carbon footprint calculation

Emission Factors: Each category of spend represents a significantly different type of purchase and resulting emission factors. Durable goods typically have higher carbon intensities per dollar spend, but also tend to last longer. Services on the other hand tend to have lower carbon intensities per dollar spent while also being used for shorter periods of time. The emission factors from each category are based on economic input-output life-cycle assessment combined with the latest country-specific economics and emissions data, aligned with the industry definitions and emission allocation used by the U.S. EPA (Carnegie Mellon University Green Design Institute 2021; Yang et al. 2017).²

Table 2. Emission factor data by category used in the personal carbon footprint calculation

Results

Based on the data and calculation framework listed above, the total annual CO2e emissions generated by the average U.S. individual’s other goods and services spending are 2,510 kgCO2e/year. 

Food

An individual’s dietary preference is another important factor impacting their GHG emissions and is an area of life. Different foods have different GHG emissions associated with them based on how the food is grown, the inputs to grow the food (e.g., water, fertilizer), the length of time to produce the food (e.g., animal food sources), how it is harvested, and how it is moved from farm to the point of sale (grocery store, restaurant).

Calculation Methods

The food GHG emissions are estimated on an annual basis based on the formula:

GHG Emissions (kgCO2e) = Dietary Emission Factor (kgCO2e/person/year)

Calculation Data

Diet Emission Factor: The emission factor for food is specific to the United States food system and represents the typical U.S. consumption patterns based on Kim et al. (2020). The modeled diets in Kim et al. are based on a 2,300 Calorie diet and are thus adjusted to typical U.S. individual consumption using the National Health and Nutrition Examination Survey (NHANES) most recently available dataset and adjusted to account for losses from production to consumption (National Center for Health Statistics 2018; Kim et al. 2020). 

Results

Based on the data and calculation framework listed above, the total annual CO2e emissions generated by the average U.S. individual’s diet are 2,058 kgCO2e/year. For the vegan scenario, the emissions are estimated to be 323 kgCO2e/year.

Financed Emissions

An individual’s banking and investments also impacts their GHG emissions, not by direct emissions like using gasoline for their car, but indirectly through the companies, organizations, or entities that the bank funds via the bank’s loan portfolio or the investment funds directly as debt or equity. 

Banking

Calculation Methods

The financed emissions are estimated for a particular year and scaled by the total checking and savings account balance an individual holds based on the formula:

GHG Emissions (kgCO2e) = Balance ($) x Bank Financed Emission Factor (kgCO2e/$/time)

Calculation Data

Account Balance: The average total checking/savings account for a family was $62,410 (median value of $8,000) based on the 2022 Survey of Consumer Financials completed by The Federal Reserve (The Federal Reserve 2023). Using the average household size of 2.5 people, this comes out to $24,964/person in the U.S. (The Federal Reserve 2023; U.S. Bureau of Labor Statistics 2021).

Bank Financed Emission Factors: The average emission factor for a traditional, carbon intensive bank is 0.24 kgCO2e/$-year, while that of a climate-responsible bank like Aspiration is estimated to be 0.057 kgCO2e/$-year (Alexander, Moinester, and Kraus-Polk 2023).

Results

Based on the data and calculation framework listed above, the total annual CO2e emissions generated by the average U.S. individual’s banking are 5,990 kgCO2e/year and 1,423 kgCO2e/year for a traditional bank and a climate-responsible bank, respectively. 

Investments

Calculation Methods

As with the banking financed emissions, the investment financed emissions are estimated based on the total investment account balance an individual holds per the formula:

GHG Emissions (kgCO2e) = Balance ($) x Investment Financed Emission Factor (kgCO2e/$/time)

Calculation Data

Account Balance: Per the U.S. Federal Reserve, this was around $489,000 for the average household, or $196,000 on a per-person basis after using the average household size of 2.5 people (The Federal Reserve 2023; U.S. Bureau of Labor Statistics 2021).

Investment Financed Emission Factors: Unfortunately, the carbon emissions generated by various investments and companies is still not widely available to the public. This data challenge makes it more difficult to accurately assess the impact of investment choices. However, based on the data available in Aspiration’s Redwood Mutual Fund, the scope 1 and 2 CO2e emissions intensity per dollar invested in the Redwood Mutual Fund is 16.72 tCO2e per million USD invested while the reference index (S&P 500) was 32.88 tCO2e per million USD invested as of 12/31/2023 (UBS 2023). It is important to note that scope 3 emissions are not included in these emission factors, making them significantly lower (since the emissions associated with burning any oil products the companies sell, like gasoline in a car, is not included in these factors). 

Results

Based on the data and calculation framework listed above, the total annual CO2e emissions generated by the average U.S. individual’s equity investments are 6,438 kgCO2e/year and 3,305 kgCO2e/year for a S&P 500 investment and a Redwood investment, respectively. 

Results

Putting all this together, Figure 1 shows the total personal carbon footprint of an average U.S. individual is nearly 28.8 tCO2e/year. The direct emissions from the individual’s lifestyle account for approximately 16.4 tCO2e/year while the indirect emissions from the individual’s financial services account for 12.4 tCO2e/year, or ~43%. Figure 2 demonstrates the relative contribution of each area of the individual’s personal carbon footprint. 

Figure 1. Absolute breakdown of the average U.S. individual’s personal carbon footprint. Direct impact areas are shown in green, while indirect impact areas are shown in blue. 

Figure 2. Relative percentage breakdown of the average U.S. individual’s personal carbon footprint. Direct impact areas are shown in green, while indirect impact areas are shown in blue. 

Next, Figure 3 shows a few of the biggest actions a consumer can take to reduce their personal carbon footprint, based on the data and calculations described above. It is clear that reducing an individual’s indirect emissions of their investments and banking preferences can be one of the more significant ways they take climate action. Simply changing their bank can do more than purchasing an electric vehicle and using (or installing) solar electricity. 

Figure 3. Comparison of the climate actions an individual can take and their impact on reducing the individual's personal carbon footprint. 

Comparison with Other Reports and Data

For completeness, the bottom-up analysis included in this methodology document is compared with a few, high-profile reports to readily address any discrepancies between them. 

Project Drawdown: Saving (For) The Planet: The Climate Power of Personal Banking 

They report an average personal carbon footprint of 16 tCO2e using a top-down reference, which aligns very well with the estimation of 16.4 tCO2e for direct emissions of an individual’s lifestyle. Additionally, the diet and vehicle emissions are quite similar (Alexander, Moinester, and Kraus-Polk 2023). 

However, a few notable differences between this methodology and the one used in Project Drawdown’s Saving (For) The Planet: The Climate Power of Personal Banking should be noted, especially as it relates to the relative importance of each action: 

• Adopting a vegan diet: The “Shrink that Footprint” source claims that a vegan diet reduces the carbon footprint of the diet by 1 tCO2e, or 44% relative to their baseline of 2.28 tCO2e. This is in stark contrast to the more reputable source used here which shows an approximately 85% reduction in CO2e when moving to a vegan diet (Kim et al. 2020)

• Switch to residential solar: Project Drawdown uses a very similar annual electricity consumption (10,000 kWh compared to the 9,120 kWh used in this analysis) and average grid electricity emission factor (0.846 lbCO2e/kWh compared to 0.92 lbCO2e/kWh). However, they assume all the climate impact goes to a single individual, rather than to a household which is then divided up by the people living there. This inflates the relative impact as it appears as though a single person lives in the home.

• Switching to an EV: Project Drawdown uses U.S. EPA data for operational emissions but does not include the manufacturing emissions of the vehicle in their analysis. Electric vehicles are well known to have higher manufacturing emissions due to the battery manufacturing process, so this analysis included it to improve the accuracy of the results

• Banking Financed Emissions: Project Drawdown used the total checking/savings account for a family of $8,000 (median value) while this analysis used the average value of $62,410 based on the 2022 Survey of Consumer Financials completed by The Federal Reserve (The Federal Reserve 2023).
  

Top-Down Calculation Approaches

As noted in the Project Drawdown report above, common per-capita personal carbon footprints are reported using top-down approaches. These approaches assess the CO2e emissions of the entire U.S. and then divide by the total population to obtain a per-capita average carbon footprint. While convenient for accounting purposes, this does not always accurately reflect an individual’s personal carbon footprint, especially with regard to emissions they directly or indirectly cause beyond the boundary of the U.S. 

For direct emissions, this is relatively small and limited to international flights and consumption in other countries. However, for indirect emissions, this can be quite large. For example, if your investments fund international companies in the S&P 500, they generate emissions across the world either through their direct operations or through their value chains. Thus, the top-down methods of estimating per-capita emissions should only be compared with the direct emission categories estimated using bottom-up approaches like those used here. 

Climate Watch compiles data from the U.S. United Nations reporting and other reporting agencies together and demonstrates that these top-down models usually estimate per-capita emissions of 16.03 tCO2e (Global Carbon Project, 2019 data), 18.01 tCO2e (UNFCCC Annex I, 2019 data), and 17.72 tCO2e (Climate Watch, 2019 data) (Climate Watch 2024). The bottom-up calculations herein calculated a direct personal carbon footprint of 16.4 tCO2e, very much in line with these top-down estimates. 

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Footnotes

1 Ever looked at an airplane in flight and wondered what that line-shaped cloud trailing from behind is? Those human-made clouds can cause additional warming beyond just the GHG emissions emitted by your flight.

2  The emission factors broadly include all transportation and distribution emissions, including last-mile delivery to the individual’s home, based on the economic input-output framework. Thus, last-mile delivery emissions are not explicitly added to the GHG emission calculation.