To create this interactive, we used readily available datasets to estimate the lifecycle global warming potential, or GWP, of each choice, measured in units of kilograms of carbon dioxide equivalent emissions (CO2e).
GWP is an aggregate measure of greenhouse gases, including carbon dioxide, methane, nitrous oxide, and fluorinated gasses. Different gases have different impacts — for instance, methane traps 25 times more heat than carbon dioxide. So 1 kg of methane equals 25 kg of CO2e. As a benchmark: 1 kg of CO2e is equal to 2.5 miles driven by a typical passenger vehicle, and one mature tree absorbs 21 kg of CO2e in a year. (The US Environmental Protection Agency assumes that a typical vehicle has a fuel economy of about 22.0 miles per gallon and drives approximately 11,500 miles per year.”)
Numbers are rounded to the nearest 0.1 kg.
For more on carbon equivalents, see this overview from the US Environmental Protection Agency and this EPA greenhouse equivalencies calculator.
We constructed our scenarios to uncover the hidden GWP impacts, over time, of different consumer decisions. The research to compile the GWP for each decision was not meant to be exhaustive, but complete to the point of being instructive, using sources available to anyone.
For our wedding scenario, unless otherwise noted, we derived GWP figures from this freely available database.
We used this Martha Stewart guide to benchmark standard wedding sizes.
To calculate the impact of guest travel, we used sources cited in this article by Northeastern University media professor John Wihbey.
Because guests come from different distances, we estimated the carbon dioxide impact of flights based on this flight calculator.
We assumed this breakdown in distance traveled:
- 10% flying within 300 miles
- 50% driving within 25 miles roundtrip
- 30% driving 25-50 miles roundtrip
- 10% driving 50-75 miles roundtrip
- 20% flying 300 miles
- 10% flying 300-1,000 miles
- 40% driving within 25 miles roundtrip
- 10% driving 25-50 miles roundtrip
- 10% driving 50-75 miles roundtrip
- 10% driving 75-100 miles roundtrip
- 100% trans-Atlantic flights
To calculate meals, we assumed that 100 percent of guests would choose either a beef, chicken, or vegan option.
To determine the GWP of drink choices, we used this economic input-output model, associating dollars spent in different sectors of the economy.
- Soft drinks: Soft drink, bottled water, and ice
- Beer: Breweries and beer
- Wine: Wineries and wine
- Spirits: Distilleries and spirits
- 70% soft drinks
- 20% beer
- 10% wine
- 30% soft drink
- 40% beer
- 20% wine
- 10% spirits
- 10% soft drinks
- 40% beer
- 30% wine
- 20% spirits
To assess the GWP of different wedding centerpiece options, we first looked into an assessment of the emissions associated with lighting candles published in the Christian Science Monitor in 2009. We assumed that four paraffin candles would be placed on each table seating eight, and would be left to burn for around two hours.
We found an analysis of the carbon footprint of cut flowers published in 2019 by British flower-growers cooperative, Flowers on the Farm. We assumed that each table seating eight would be adorned with a bouquet featuring eight Kenyan-grown roses.
Dinner party scenario
For our dinner party scenario, unless otherwise noted, we calculated GWP using this freely available database.
We assumed 10 people total at the dinner party, eating an equivalent of two serving sizes apiece for each course.
For our vacation scenario, unless otherwise noted, we calculated carbon equivalent data using this freely available travel calculator. We assumed a vacation for two people for five nights.
To calculate the GWP of driving, we assumed that the travelers would share a car — so they would split the carbon impact of the drive in half.
To calculate the GWP of flying, we used this calculator to estimate the travel impact of two coach seats on an airplane — essentially, the percentage of the plane each traveler is taking up. (A first class seat would have a larger climate impact, because it takes up a greater percentage of the plane.)
For the domestic flight, we calculated the carbon impact of two roundtrip direct flights from Boston to Miami. For the international flight, we calculated the carbon impact of two roundtrip direct flights from New York to Rio de Janeiro.
To calculate the GWP of lodging, we used figures from the following sources:
- Hotel, at 31.1 kg CO2e/room/night
- AirBnb (63 percent of the impact of staying at a hotel)
- For recreation, we assumed an hour of rental of jet skiing ($90/hour) or surfing/paddle boarding ($15/hour)
For dining, we assumed a payment of $80 per person per day — $10 for breakfast, $20 for lunch, $50 for dinner.
We calculated the cost of supermarket shopping based on this data from the U.S. Department of Agriculture.
We calculated the cost of dining out using the average cost of food for a person in the 19-to-50-year-old range. Because food on vacation tends to cost more, we added an extra 10 percent to the calculation, resulting in $90/week or $13/day/person.
For the 50/50 shopping-and-dining-out option, we used the average GWP cost for each option.
Number of trees planted is based on seedlings grown for 10 years, from the EPA gas equivalencies calculator.