One of my American readers sent me an email on global warming a while ago. She was a bit annoyed with the fact that Europeans often point out that the United States has 4% of the world’s population and contributes about 25% of the world’s global warming gasses. In her first email she linked to a website with information on the twenty largest emitters of carbon dioxide. The idea was to show that Europe’s biggest polluters aren’t that much better than America. I share her frustration with Europe’s anti-American blame game, but I couldn’t buy her argument since the American share of global CO2 emissions is so much bigger no matter how you calculate.
About a week later, my email friend came up with another explanation that seemed plausible by the first look at it. She suggested that the emission of carbon dioxide was linked to landmass. I quote:
Although we figure out CO2 emissions per capita usually—we really need to take into account land mass.
For example picture a square drawn that is one mile square, with lines connecting each point. That would mean six lines about 1 mile each (actually the middle diagonal lines are more like 1.4 miles)—so a total of about 7 miles of lines. Pretend 6 people live on the points of the square. Picture those lines as the distance people would have to travel from each point to each point on that square to get all the points connected, which would be 7 miles.
Now picture the same square as being 2 miles big with the same 6 people living on it and taking 6 trips to connect each point. That would be a total distance of about 14 miles traveled.
As you can see, we in the US could drive the same amount of trips per capita with the same cars and the same gas mileage, but even if we did all those things, because our country is larger, we would still be driving twice as far and emitting twice as much CO2 as the EU. I haven’t figured out yet the exact difference in size between the land mass of the top 20 emitters of CO2 gasses in the EU and the US, but I’m sure it’s much larger (excluding Russia) and I’m sure there must be an effect to this.
Like I said, this seems plausible. But when I studied the figures, I realised that the argument wouldn’t wash.
According to the CIA factbook, Sweden has a population of 9,016,596 people and a landmass of 410,934 sq km, whereas the US has a population of 298,444,215 and a landmass of 9,161,923 sq km. When I divide the population by land mass I get 21.4 for Sweden and 32.6 for the US. Now, if we look at the graphs below, we see that the CO2 emission would suggest something completely different. As we can see here, Sweden (top graph) releases less then half the amount of CO2 per capita. (Click on graphs for sources.)


To find an explanation, I turned to CIA’s figures again. I thought that perhaps the income per head could explain the difference. It couldn’t. On average, an American citizen earned $43,500 in 2006 while a Swede made about $31,600. A significant difference, but not enough to explain the huge gap in carbon dioxide emissions.
Update: Two readers have emailed me to say that I’m doing this the wrong way. According to them, I should extract the square root of the land area in order to learn the average distance. I honestly don’t understand why this would be more accurate, but I sense that they are on to something. Perhaps I’m a bit slow. Maybe I get it when I’ve had good night’s sleep.