Great Scott, how did I miss this?  Late last month, the EPA released a draft greenhouse gas inventory, showing that net climate warming emissions from the US fell by a whopping 15 percent from 2000 through 2009.

A 15 percent decline?  Wow. Just wow.

But the story gets even more dramatic.  Over the same period, the US population grew by about 9 percent.  Combining the two trends, net per capita GHG emissions fell by 21 percent over the decade.  And most of that reduction occurred prior to 2007—when the economy hadn’t yet slumped, and before energy prices hit the roof.

In case it’s not clear, these reductions made a huge difference.  If we’d kept going at 2000’s per capita levels, the nation would have released about 1.5 billion additional tons of CO2 into the atmosphere in 2009.  To give you a sense of the scale, 1.5 billion tons of CO2 is…

  • More than the direct annual CO2 emissions from all fossil fuels consumed in homes, businesses, and industries in the entire US nation;
  • Over four-fifths of the yearly CO2 emissions from fueling the nation’s cars, trucks, trains, boats, and airplanes.
  • About one and a half times as much CO2 as is soaked up each year by the nation’s forests, grasslands, and other ecosystems.

I’ll dive into the numbers in a moment, but my first reaction to this is simple amazement—not so much at the size of the drop, but more at the fact that it drew so little attention from the press.  I might have missed it, but I didn’t even see the story mentioned by major climate bloggers.  Why is that?  Is climate change now such old news that even a big data release like this elicits only a shrug?  Were people afraid to discuss the story, figuring that it would seem like crass gloating over a sour economy?  Or has the professional news media become so depopulated that nobody even had time to cover the story?

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    • A few notes on the numbers themselves (pdf link). 

    First, like all emissions inventories, this one should be regarded as an estimate, not the gospel truth.  That’s especially true, since it’s still a draft.  In my experience, EPA’s inventories are comprehensive and use good data, but good doesn’t mean perfect; so I have to assume that some parts contain pretty wide error bars. 

    Second, a good chunk of the net emissions reductions are due to an estimated increase in carbon sequestration by forests—which actually tames my excitement over the trends. I haven’t read deeply enough into the causes for the increase in the sequestration estimates.  But sequestration can be a particularly difficult trend to measure, with the widest error bars.  And lots of forces, from weather to temporary shifts in timber and crop prices, can have a huge impact on annual sequestration rates.  So while an increase in sequestration is good news, it’s not necessarily a trend that will continue into the future.

    Third, there’s a big story that this inventory misses completely.  The numbers only cover emissions from within the US itself.  So international emissions that are made on our behalf — say, to manufacture goods that we import—are missed entirely.  It could be that at least some of the emissions reductions from the US inventory were simply shifted overseas.  But it’s anyone’s guess how big that shift really was.

    Still, despite these caveats, I’ll take my good climate news where I can take it.  And an emissions decline of this magnitude is certainly good news.