It’s often shrugged off, but what explains the difference with Europe, exactly?
Greenhouse gas emissions are most commonly reported at the national level, which tends to make us compare nations to other nations. This makes some sense, as national policy can significantly influence emissions trends. But it’s easy to forget that borders are just lines on a map, and some lines have considerably more people inside them than others. The citizens of Luxembourg don’t ensure their country’s low carbon emissions because they’re lightyears ahead of the people of China in terms of efficiency—there are just a whole lot fewer of them.
In order to make more meaningful comparisons, you obviously have to calculate emissions per person. And when you do that, the United States really sticks out. (As does Luxembourg, by the way.) It’s not surprising that per capita emissions in the United States are much greater than in India, where millions of people still lack electricity. But why are they also much greater than in the wealthier Western nations in Europe?
To answer that question, we need to do more than divide a national total by population. We need to break down the contributions to a person’s carbon footprint—the emissions behind the things we buy and do. Doing that in a detailed way is a challenge, and researchers haven’t been at it that long. “A lot of the research that’s been done has been done quite quickly [with] available data and resources,” UC Berkeley’s Chris Jones told Ars, “And there really is a lot of work to do.”
Some of that research breaks national or (regional) economies into sectors to look at what comes in and goes out in each category. That also helps account for things like moving your manufacturing to another country. Other studies try to work from the bottom up, getting people to fill out surveys or even log diaries of their purchasing habits—an interesting but labor-intensive (and expensive) source of data.
A third approach combines more types of data into an econometric model, applying demographic information to the big economy-scale stuff. “And then once you’ve done that, kind of the cool thing is you can now scale emissions to any location within countries,” Jones said. With data on things like home size, power plants, climate, and vehicle ownership, a more recognizable carbon footprint can be calculated for the community around you.
But any way you estimate it, the average American carbon footprint is in the ballpark of double that of the average European. (For the purposes of this article, “Europe” will refer to the pre-Brexit EU group of nations.) This huge difference is sometimes brushed off as a simple consequence of Europe’s greater population density. It’s not that simple, though—even the efficient high-rise cores of the biggest US cities can barely dip into the range of European national averages. So what exactly is it about American homes, communities, and behavior that adds up to explain this gap?
Excuse me?
In 2014, Chris Jones and his colleague Daniel Kammen published a map of US household carbon footprints by ZIP code based on that econometric method—the most detailed estimate out there. The US is pretty varied in a number of ways, which produces some regional patterns.
Emissions from electricity use are higher in areas that still had coal-dominated grids at the time, while home heating is a much larger factor in Northern states with colder winters. But most interesting is the pattern within and around major cities.
The average American household footprint is a little below 50 tons of CO2 per year (actually “tons of CO2-equivalent” to include other greenhouse gases), but that number can drop to around 30 in city centers—closer to the average of a country like Germany. American cities are surrounded by sprawling suburbs, though, which swing very much in the opposite direction, going as high as 80 tons.
There are a number of reasons for that, including much larger homes and lengthy commutes. But even if European cities tend to trade suburban sprawl for a more concentrated area of medium density, it’s not like Germany is a continuous megacity. Even US ZIP codes with considerably higher average population densities than European nations have higher household carbon footprints. What’s going on here?
Is it the weather? Maybe Americans have to contend with colder winters and hotter summers? Not so. Heating and cooling demand is calculated in terms of “heating degree days” and “cooling degree days”—the number of days your thermostat kicks on combined with the difference in temperature inside and outside. On average, the United States does have more cooling degree days in the summer than Europe’s average. But Europe has a larger lead in heating degree days. So if anything, it’s European homes that have the larger heating/cooling demand, on balance.
(As an interesting sidenote, heating degree days are decreasing and cooling degree days are increasing as Earth’s climate warms—and by more than you might think. Europe’s average heating degree days have dropped about 15 percent since 1980. California’s data, as an example, looks similar. And because home cooling runs on cleaner energy than heating in California, the net effect of climate change has reduced the average footprint a bit.)
What about industry? If the EU outsourced more of its manufacturing and materials industry, that might make it look cleaner than it really is. In reality, the US and Europe are relatively similar in this regard. If you go back to the national emissions chart above, the dashed lines show the effect of adjusting for imports. That boosts US and EU per capita emissions by about the same amount (while decreasing China’s). And carbon-footprint estimates largely capture this, anyway, by assigning you the emissions associated with your consumption of goods and services.
Perhaps it’s the energy mix? After all, a cleaner grid would shrink your footprint even with no change in behavior. But that doesn’t explain much here, either—at least when comparing the averages for these two regions.
There are exceptions at smaller scales, like France’s nuclear-dominated grid or Switzerland’s grid, which is powered almost entirely by hydroelectric dams and nuclear power. And in the United Kingdom, the rapid replacement of coal with renewables over the last decade has reduced per capita emissions considerably. UK households used to have an above-average carbon footprint for the EU; that’s no longer true.
Tracking a Bigfoot
So let’s break down the four factors that best explain that larger American carbon footprint, starting with transportation. The United States loses (wins?) on just about every possible metric. First, Americans own more vehicles—there are over 800 of them per 1,000 people. Countries like Germany, France, and the UK average around 500.
Second, vehicles in the US have lower average fuel efficiency. Even last year, new vehicles sold in the US averaged around 25 miles per US gallon (about 11 kilometers per liter). For the EU, the average is much higher at about 45 miles per US gallon (19 kilometers per liter). That’s partly due to a preference for larger vehicles (including a growing share of SUVs and crossovers) in the US, but it’s also due to the greater popularity of diesel engines in Europe.
And third, those more-numerous and less-efficient American vehicles also drive more. The average American vehicle travels over 11,000 miles (over 18,000 kilometers) per year. The average EU vehicle travels around 7,500 miles (12,000 kilometers) per year, instead. Accounting for modes of public transit, as well, the total puts the American transportation footprint around 50 percent higher than the average European.
The next major factor is housing. Single-family detached homes are more common in the US, although the exact carbon footprint implications of this aren’t well quantified. The numbers do clearly show that American homes are bigger, though. The median American home is in the neighborhood of 1,600 square feet (150 square meters), while the median European home is probably closer to half that. (In both cases, new homes have trended north of those numbers.)
That might even be reflected in the average number of rooms per person. The US comes in near the top, at about 2.4 rooms per person, while EU nations tend to fall in the 1.4 to 2.1 range. (However, there are some differences in the definition of “a room” that probably make this difference smaller than it seems.)
Stuff
Bigger homes obviously require more energy to heat, cool, light, and so on. They also give you more space to fill with stuff.
Which is why consumption of goods and services is another big factor. Here, we really have to rely on economic modeling to connect the dots to the emissions behind our purchases. There are some obvious things that can drive higher consumption—like wealth—but there are other interesting correlations in the data.
“Home size is one, but home ownership is another. So if you own the home, you’re much more likely to purchase furniture, purchase flooring, have yard services, and other types of services for the home,” Jones told Ars. “People with higher education, you might think they might be lower carbon because they’re more aware of climate change or something, but no, they spend, they travel more, they eat out more, there are more entertainment services… They spend way more on education, as you might expect—even healthcare. And it’s kind of like an expression of social status perhaps, but higher-income households tend to consume more overall, [even] controlling for income and household size and home size and all those other factors.”
Consumption-footprint estimates vary but come out significantly higher in the US. As a percentage of total household carbon footprint, consumption might actually be a thinner slice of the pie in the US, but by mass it’s still more pie.
Rounding out this discussion of carbon pies is, appropriately, diet. There are distinct differences in diet between countries, and cultural patterns are clear. Seafood is a much bigger part of diets in Iceland, for example, few nations eat pork like Germany, and Scandinavians really love dairy. But where the US stands out from most other nations is in beef consumption, and beef has a huge carbon (and water and land) footprint.
As a result, the carbon footprint of the average American diet is about 20-percent greater than that of the French and 60-percent greater than that of the Germans.
Totaled up, the average American carbon footprint is around one-third transportation, one-quarter housing, and one-quarter purchased goods and services, with diet comprising the remainder. In terms of tons of CO2, the biggest differences with Europe are in transportation and housing, which make up about 15 of the 20-tons-per-year overall gap in the estimates shown below.
One size fits all?
So could the United States be more European with its carbon footprint, or would that require a lifestyle most Americans would find foreign? There is, in fact, a considerable amount of practical room for reduction.
In a 2018 study, Chris Jones, Daniel Kammen, and UC Davis researcher Stephen Wheeler closely analyzed California’s potential. They estimated the impact of a range of changes through 2050—things like focusing new home construction on urban infill, increasing the efficiency of vehicles, homes, and industry, dietary shifts, and a cleaner electric grid. In total, this scenario reduced average footprints by 65 percent.
As an individual, some of these things are more or less out of your hands, like power plants and industry. Others are in the realm of government incentives to encourage or enable certain behaviors, like fuel-efficient vehicles. But plenty are personal choices you can make when your situation and resources allow.
Since your own carbon footprint may not look like the American average in every category, online calculators can help identify the actions with the biggest carbon payoff. A good one can be found at CoolClimate—a site set up by Chris Jones and Daniel Kammen that is home to maps and calculators for two of the studies discussed above.
Starting from a default American household with a carbon footprint of 48 tons per year, here’s one scenario that gets you to a European average. Trading up to a pair of more fuel-efficient 40-miles-per-gallon vehicles and trimming their annual miles driven to 8,000 each drops your overall footprint to 39 tons. Reducing the miles of air travel from 3,700 to 800 gets you down to 38 tons. If your electric utility offers a 100-percent renewable energy plan (or if you want to invest in solar panels that cover your usage), that reduces the footprint to 33 tons.
Reducing your consumption of meat and eggs from 2.6 servings per day to one serving brings another 2 tons of reduction. If you can find a way to take about 20 percent off your goods and services footprint—either by choosing less emissions-intensive options or simply cutting back on purchases—that will take another 3 tons away. And finally, reducing fuel usage for heat by about 13 percent—which could be done by turning the thermostat down a few degrees and/or improving insulation—buys another ton. All together, these things bring the footprint down from 48 tons per year to 27 tons.
There are obviously many other ways to get there. Switching to an electric vehicle could be a big efficiency boost, for example, as could switching your home heating to an electric heat pump. And getting your electricity from renewable or nuclear generators would reduce their emissions even further. Or you could lower your home energy demands simply by moving into a smaller place next time you need to transplant. It’s all about identifying opportunities, balancing your needs and priorities, and finding things that work for you.
That also means finding things you’ll actually follow through on. “A lot of times, I get people to say… ‘We’ll just, instead of having three vehicles, we’ll just have one,'” Jones said. “OK… do that, but just keep in mind that took, like, zero effort for you to do in the calculator. But in real life, it’s a big change.”
These are all things you might be able to do if you, personally, want to walk with a lighter carbon footprint. But it’s important to note that this isn’t the solution to climate change, even if it helps. Rapidly reducing emissions to zero is impossible without societal, system-level changes, which are bigger levers with broad impacts. So an entirely different path to reducing your household carbon footprint also exists—working to effect top-down change.
Contact Information:
SCOTT K. JOHNSON
Tags:
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Contact Information:
SCOTT K. JOHNSON
