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As the public conversation about climate change gets increasingly serious, many Americans may be wondering: How do my individual choices affect climate change?
Household consumption—food, housing, transportation, apparel, and other personal services—is an important contributor to greenhouse gas emissions. Everything you eat or wear, every time you drive, contributes to total global emissions. The typical American’s annual per capita carbon footprint is more than five times the world per capita average.
A study by our research team, including Kaihui Song, Shen Qu and Sai Liang, published on September 10, sheds light on the global carbon footprint of U.S. households.
Some activities have a bigger impact
We looked at data from 1995 to 2014 from the U.S. Consumer Expenditure Survey, as well as the World Input-Output Database. We looked at the total global warming potential of all greenhouse gas emissions, not just carbon dioxide, as measured in their “carbon dioxide equivalent.”
We found that over 20% of all U.S. emissions are directly attributed to household consumption. If you consider indirect emissions, this figure is closer to 80%.
Let’s zoom in on the latest available annual numbers, mostly from 2009, which give a better sense of the impacts.
U.S. households generate 5.43 gigatons of carbon dioxide equivalent emissions every year. About 82.3% of those emissions are produced domestically.
The remaining emissions are generated outside the U.S. These emissions come from global supply chains. For instance, the family car might have been manufactured abroad. So emissions from manufacturing of the car are created outside the U.S., but emissions from the tailpipe are domestic.
Transportation and housing contribute over 60% to the total domestic carbon footprint of U.S. households. Supply chain emissions from services–such as health care, banking, and lodging–and food contribute the next largest amounts.
Food, furnishings and supplies, and clothing are the three largest drivers of overseas emissions from U.S. households.
China bears the brunt of overseas emissions
The overseas carbon footprint driven by U.S. households is distributed disproportionately among countries. The most considerable portion of overseas carbon footprint of U.S. households is released in China, followed by Canada, India, Russia, and Mexico.
The overseas carbon footprint from Mexico is largely driven by food consumption in the U.S., while fuel consumption in the U.S. was the main driver for overseas carbon footprint from Canada and Russia, where the U.S. got the majority of its imported oil products and natural gas in that period.
While the most substantial amount of the U.S. overseas carbon footprint is from China, it is only 3.0% of China’s domestic emissions. The majority of China’s emissions comes from the activity of its inhabitants, as well as consumption in other countries beyond the U.S.
On the other hand, Canada, Mexico, and Taiwan trace a sizeable proportion of their domestic emissions to U.S. household consumption.
Wealthier families have a larger footprint
A household’s carbon footprint generally increases with its income, ranging from 19.3 to 91.5 tons of CO2-equivalent annually. The average carbon footprint of the wealthiest households is over five times that of the poorest.
In 2009, households with less than $30,000 annual disposable income made up 25.7% of the total U.S. population, but were only responsible for 19.3% of U.S. households’ carbon footprint.
On the other hand, wealthy consumers with more than $100,000 annual household income accounted for 22.3% of the total population but were responsible for nearly one-third of households’ total carbon footprint.
The Great Recession caused a dip
U.S. households’ carbon footprint had been steadily growing from 1995 until 2005, when it began to plateau.
In 2009, the combined domestic and overseas footprint dropped by 8.5% from the previous year, mainly due to the Great Recession.
The share of overseas carbon footprint in total carbon footprint of the U.S. household consumption had been rising steadily and peaked at around 20% in 2006. After 2006, the share of overseas carbon footprint started to decrease, as imports slowed down before the recession.
Transportation makes the biggest difference
The variations of household carbon footprint from 1995 to 2014 were largely driven in transportation use, including emissions from vehicle manufacturing, fuel, and public transportation.
Transportation emissions, both per capita and per household, have continued to rise over time. This is despite significantly reduced tailpipe emissions from vehicles and nearly 30% improvement in fuel economy of cars in this period. Mandates and standards, such as Corporate Average Fuel Economy (CAFE) at the federal level and Zero-Emission Vehicle (ZEV) at the state level, enabled this rapid progress.
So what’s causing the emissions to keep rising? People want to travel more and are more likely to own more household vehicles. Meanwhile, vehicles have a lower average number of occupants. Mass transit and active modes of transportation, like bike riding, are growing slowly.
In 2016, for the first time in history, the emissions from the U.S. transportation sector surpassed the power sector emissions. This fact along with our observation from household carbon footprint from transportation underscore the importance of policy efforts related to emissions from the transportation sector.
–Morteza Taiebat is a Ph.D. Candidate in Environment and Sustainability, University of Michigan. Ming Xu is an associate professor at the School for Environment and Sustainability, University of Michigan. This article is republished from The Conversation under a Creative Commons license. Here’s the original article.
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6 Comments
Good ole 'Merica, whose thought pattern is 'more is better' and 'bigger is best':
Make cars more efficient. Progress! Then own more cars.
Make houses more efficient. Innovation! Then make houses bigger.
You can see that ^ trend in the Income Level chart.
We need much higher fossil fuel costs (with tax credits to not worsen income disparity). Unfortunately, people love low fuel prices and politicians accommodate them.
Wrt green building, "building close" is often more important than something like better-than-code insulation.
Does transportation in this study include flying and intercity train trips? I clicked through to the original study, but as far as I can tell, it doesn't include passenger flights and train trips.
Mass transit (so city buses and intercity rail) aren't always included in these studies. Other studies have included mass transit alongside passenger jets, and the general concensus has been:
+ new wide body jets (so 300+ passengers) can be efficient for long haul, like West Coast to East Coast US or across the pond (US to Europe). It's the short flights and small aircraft that have the big inefficiencies.
- intercity rail in the US doesn't haul enough passengers to make a dent. Amtrak's Acela line has the largest volume of passengers, but the rest of the country doesn't haul enough. European and Japaense high speed rail is a very different story, but this article is about the US.
- city bus / light rail is similar story to intercity rail: not enough passengers.
I find it fascinating (and annoying) that my fellow Americans will drive to an airport, put up with TSA or buy their way into avoiding TSA, wait around for 2hrs ahead of scheduled departure in uncomfortable seats, only to be delayed on departure for various reasons, boarded onto dirty planes that got a "turnaround" sweep, shoved into the aircraft like fish in a tuna can, have to pay extra for humane legroom, -- all to sit on the tarmak and wait even longer for local air traffic to clear.
Yet Americans won't take a bus? or a train?? I've taken 4 train trips this year: I arrive 15mins before departure, the only security is a random police dog sniffing as you pass by, the train departs on time -- depsite what FUD people have spread --, I make myself comfortable in a HUGE chair with power outlet that's not crammed into a place only a gymnast can reach, and the train arrives within 5mins of schedule.
Americans -- and their fear of mass transit. I took a coworker on a light rail in a major US city once: he said never to do that to him again, and so he always rents a car. Pfft.
Trains really only work as an alternative if travel time is 4 hours or less. Unfortunately trains still require massive subsidies.
In 2017 Amtrak (The only interstate passenger train operator in the US) earned about 36 cents a passenger mile in fares, food, and beverages. Direct operating costs averaged 52 cents a passenger mile, while unallocated costs added another 13 cents per passenger mile.
For airlines the average cost per seat mile is around 7 to 8 cents for low cost carriers and 11 to 12 cents for network carriers.
Where did you find the revenue and operating costs for Amtrak versus airlines? Because some of those numbers sound dated. See https://m.amtrak.com/h5/r/www.amtrak.com/stakeholder-faqs
Amtrak is not operating in deep red ink. It has been floating on revenues for their operations for several years after cost cuts. Their problem is that even when they get above their small operating deficit, that leaves no revenue left over for capital improvements. The news picks up on sound bites when Amtrak asks for capital funding, and so the public gets half the story. "Massive subsidies" for Amtrak is a gross inaccuracy of the CBO (Congressional Budget Office) transportation budget.
The public fails to remember that their taxpayer dollars now pay for all of those TSA agents at airport, which is some 50,000 federal employees added to the payroll after 9/11. That's in addition to the critical functions of airspace control for commercial passenger Jets, like the FAA, that have also subsidized by American taxpayers for some time. The Federal transportation budget is large for many types of transport, and aviation is just as guilty as rail in asking for funding.
What's worse for aviation is my example of TSA: technically that payroll falls under the department of Homeland Security not the Department of Transportation, so we don't even see those kinds of numbers in reports such is those the CBO releases for transportation budgets. httpss://www.cbo.gov/publication/54539
Were all of these factors used in calculating that passenger revenue rate?
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