In the world of climate geeks, there was some serious hubbub a couple of weeks ago when researchers with the Vulcan Project produced a carbon-doixide emissions map of the U.S. Using direct CO2 measurement, we saw this first-of-its-kind map. (Click for a larger version).co2 emissions - vulcan

Perhaps for obvious reasons, the map looks a lot like a population density map, since the largest share of cars, buildings, and industry — and hence CO2 — tend to be where the people are. But by turning major cities red, it leads one to precisely the wrong conclusion. Looking at the map, you might think that urban areas are the nation’s big carbon problem, while the dessert West and the Rockies are doing something really right. I suppose that’s true on some level: there’s not a lot of carbon being emitted in the wide open spaces of the West.

The good people over at Wired got wise to the situation and agitated for a map that factored in population density. Check out what happens when the researchers add population density to calculate per capita carbon emissions. It’s a completely different story.

co2 per cap - vulcanOn this reading, the real problem is the West, particularly the Southwest. The nation’s cool spots are the relatively densely-settled eastern areas. (Data-oids take note: the population density methodology is imperfect – and the researchers acknowledge it – but it’s roughly right.)

Now, we know that per capita emissions don’t matter a whit to the atmosphere. All that matters is the total amount of carbon that goes up in smoke. But without understanding the population-based side of the equation, we’re unlikely to understand how to fix our emissions problem. The key is not for our economy to function like it does in West Texas or Wyoming, but more like it does in cities.

Cities, as it turns out, are a major climate solution. That becomes clear when you think about how we use energy. Folks in cities drive less often, and when they do drive, they don’t drive as far. They tend to live in smaller spaces – square footage is expensive – which means lighting fewer rooms, and less heating and cooling too. Plus, city life often means sharing walls (and floors and ceilings) which makes for tremendous heating efficiencies.

In fairness, there’s lots of other stuff going on in a map like this. Places with energy-intensive industries-aluminum smelters, oil refineries, and paper mills-get dinged because the totality of those emissions get attributed to the people that live near them, even though the goods they produce get consumed across the nation. Similarly, places that are nearby coal-fired electricity generators aren’t likely to do so well either, even though people in far-flung places consume that dirty electricity too. But lifestyle matters. A lot. And maybe the most powerful predictor of your climate impact is simply this: whether you can see a sidewalk from where you’re sitting now.

Full explanation, with links to lots of other cool stuff, can be found here.