Carbon dioxide output from the United States will peak and then begin to fall in just a few years, according to the numbers derived by John Whitehead at the Environmental Economics blog. The reason is that carbon intensity -- the amount of carbon produced per dollar of GDP -- is dropping at a rate faster than GDP is growing. At the current pace of intensity reduction, CO2 output in the US will peak in 2008, and begin a gradual decline thereafter. (We previously discussed carbon intensity here.)
This is good news for a number of reasons, not least that it suggests that the current biggest contributor to the greenhouse effect could, with a bit more effort, achieve a far more dramatic reduction in CO2. How to do this is a mainstay of discussion at WorldChanging; here's a look at some of the numbers underlying these options. CO2 intensity is a function of two components: the energy required per dollar equivalent of GDP (or use efficiency of energy); and the CO2 output per MW equivalent of energy (or carbon efficiency of energy). By taking a closer look at the data, we can see which one has mattered more -- and which could stand some improvement.
The material I'm using here comes from the Energy Information Administration at the U.S. Department of Energy, which collects data from around the world for compilation and comparison. The current spreadsheets cover 1980 through 2003; I would expect 2004 data to show up (at the same URLs) by the middle of next year. I am using just a few data sources, but if you have any interest in the subject, the EIA site is a treasure trove. For the record, I recognize that the use of GDP poses problems, since the numbers become dependent upon exchange rates and GDP measurement methods; I would say, however, that this gives us a good estimate, even if the overall accuracy can be questioned.
Carbon intensity is carbon emission per GDP (XLS). The EIA uses slightly different measurements than Dr. Whitehead does on his site, and since I have direct access to the EIA data, I'm going with that. According to the EIA, the United States has seen a gradual but steady reduction in the amount of CO2 produced for every (constant) dollar of GDP. In 1980, the US put out 0.92 metric tons of carbon dioxide for every thousand dollars of GDP; by 1990, that was down to 0.70 tons/$1000; by 2000, it was 0.59 tons/$1000; and the most recent data, from 2003, has it as 0.56 tons/$1000. That's a pretty big drop -- how does it stack up against other countries?
I've picked a few nations that we talk about on a semi-regular basis as comparison: Canada, Brazil, Sweden, the UK, China and Japan. Here's what the numbers look like for those countries:
Carbon Intensity (Tons CO2/$1000 GDP) Country 1980 1990 2000 2003 US 0.92 0.70 0.59 0.56 CA 1.12 0.89 0.79 0.80 BR 0.50 0.58 0.57 0.55 SW 0.55 0.28 0.24 0.22 UK 0.70 0.53 0.38 0.37 CH 8.46 5.44 2.81 2.58 JP 0.34 0.24 0.25 0.25
Here are two charts of this, with and without China (since it messes up the curve):
A few things stand out: the US and Brazil now have very similar energy intensities; Canada is noticeably less efficient than the US; and China is both incredibly inefficient and getting better at a rapid clip. (India's numbers, if you're curious, are a bit lower than China's but not getting better as quickly.)
We've discussed these numbers before; the usual explanation for the US & Canada is that, as bigger countries, they require more driving, and driving remains heavily carbon-intensive.
Okay, let's look at energy consumption per GDP (XLS), or what I term above "use efficiency of energy." This is in BTUs (a standard energy measurement) per $1000 of GDP.
Use Efficiency of Energy (BTU/$1000 GDP) Country 1980 1990 2000 2003 US 15,174 11,901 10,081 9521 CA 24,063 20,751 18,131 17,863 BR 10,778 12,481 14,259 13,944 SW 13,175 11,334 9299 8294 UK 10,112 8153 6711 6427 CH 101,936 65,522 35,973 33,175 JP 5508 4450 4703 4605
And, as before, two charts:
These look very similar to the CO2/GDP lines. It's a little surprising just how use-inefficient Canada is; at its current rate, China may well exceed Canada's efficiency by early in the next decade.
It's clear, however, that -- with the exception of Brazil -- there has been an overall improvement in use efficiency. This isn't a surprise, as we've talked about improvements in use efficiency before, but it's good to see real numbers. These improvements come from a combination of factors: appliances and production processes using less power for the same output; changes to practices that reduce the amount of wasted energy; and changes to how we do what we do, whether it's a shift from manufacturing to services or a shift from business travel to videoconferencing. The important point is that improvements remain possible with use efficiency, and most places are getting better at it without putting much effort into the process.
But that's just half the story; improved carbon intensity also comes from reductions in the carbon dioxide we put out when we use energy. The EIA site doesn't have a global spreadsheet of this value, but it does have both overall emissions (XLS) (in megatons of carbon dioxide) and overall energy consumption (XLS) (in quadrillion BTUs, or "quads") -- figuring out CO2/Energy becomes an exercise in fiddling with Excel.
Carbon Efficiency of Energy (MTCO2/Quad) Country 1980 1990 2000 2003 US 60.7 59.0 58.8 58.7 CA 46.7 43.5 43.5 44.5 BR 46.3 38.5 40.3 39.8 SW 41.9 24.3 25.7 26.8 UK 68.8 63.7 56.9 57.4 CH 83.0 83.1 78.1 77.9 JP 61.6 54.4 52.3 53.8
And the chart, including China since it's not as far off from the rest as in the previous examples:
Unlike the other charts, which generally show a clear improvement since 1980, carbon efficiency appears to have been more-or-less constant over the past 25 years or so. A few of the selected countries do show signs of improvement; Sweden has the most notable change, cutting its CO2 emissions/energy by almost half from 1980 to 1991 -- anyone have a good explanation?
What this chart tells us is not a surprise. By and large, few locations have moved away from CO2 producing energy sources to any significant degree. Clearly, this is the part of the function most in need of improvement; this chart is a way of measuring the impact of the changes we try.
Examples of what could change this chart: adoption of more renewable energy sources; adoption of plug-in hybrids on a large scale; adoption of more nuclear energy; adoption of widespread carbon sequestration projects; peak oil. In general, any new process or practice that reduces the reliance upon high-carbon energy sources in favor of low-carbon sources, or that directly prevents CO2 from getting into the atmosphere, should result in shifts on this chart. If, conversely, we adopt superficially green practices that don't actually make a big difference -- such as some kinds of biofuels -- that will also be visible here.
The last chart to keep in mind tracks use efficiency and carbon efficiency, globally:
