Greenhouse emissions

Global carbon dioxide emissions in one convenient map

Detailed map clearly shows where it’s coming from

Enlarge / Total carbon dioxide emissions from fossil fuels in 2010.

Asefi-Najafabady et al./JGR:Atmospheres/AGU

Ars Technica,

26 September, 2014

When we talk about greenhouse gas emissions, it’s usually in the form of one big number (bigger every year) representing the global total. There’s also the concentration of CO­2 in the atmosphere, which knows no borders. When it comes time to talk policy (during UN climate negotiations, for example), national totals for the top emitters will enter the conversation—too often to aid an argument that some other country should be the one to start doing all the work.

Many researchers need to zoom in much further, though, to really understand what’s going on. It’s a problem you can attack from the top—starting with national totals and spreading them across the country in some detail—or from the bottom, utilizing local measurements and emissions records.

A group of researchers led by Arizona State’s Salvi Asefi-Najafabady has produced the highest-resolution map of emissions yet, making the reality of our greenhouse footprint a little more real. It shows exactly where the most work remains to be done as we seek to unshackle ourselves from the fossil fuels that have brought great benefits, for which the bill is finally coming due.

Using a number of data sets, the researchers produced global maps of emissions at a resolution of 0.1° latitude and longitude (about 11 kilometers at the equator) for 1997 through 2010. Their approach was a combination of “top-down” and “bottom-up.” They were careful to use national emissions totals as checks, but for each grid cell they calculated emissions based on things like population density (both from census data and satellite images of nighttime lights), economic activity, the emissions intensity of that economic activity, and records from power plants.

The end result is a map showing exactly how much CO2 is emitted from the burning of fossil fuels, with enough detail to pick out individual cities.

Of course, once you have that, you could break it down in any number of ways, like emissions per capita. With 14 years of these maps, the researchers do some analysis of trends. Over the short tem, you can clearly see the effect of the economic downturn. In 2010, emissions in most areas were on the rebound as economies picked up. But while emissions were increasing in the northern half of the Eastern US, they were still declining in the southern half—the product of a lagging recovery. This is especially noticeable given that the reverse of this pattern was present in 2006.

Over the long term, the growth of emissions in China, India, and several other hotspots is apparent. Many regions show slight decreases in emissions, but with growth concentrated in urban areas. The researchers illustrate geographic shifts in emissions in an interesting way, calculating a “center of mass” for emissions each year—the balancing point around which emissions are equal. Splitting the globe into a two-dimensional map along the International Date Line in the Pacific, the 1997 center of mass was in the Mediterranean Sea, south of the heel of Italy’s boot. But by 2010, it had moved far to the east and a bit to the south, reaching Jordan, as the result of increasing emission in China and Southeast Asia.

Enlarge / The "center of mass" of global emissions, from 1997 to 2010.

Asefi-Najafabady et al./JGR:Atmospheres/AGU

Pictures are worth a thousand words, as the old saying goes. These pictures might be worth a few more. Since carbon dioxide is an invisible gas, it takes careful research to help us see our emissions in another way.