US emissions drop, old relationship between GDP and emissions has been broken for past decade

The US Department of Energy has released the estimate of US carbon emissions for 2009. And it is good news. Emissions are down, and not only because of the recession (and before anyone comments, I don’t think the recession is good news, I was speaking ONLY of the emission drop).

For 2009, the [DOE] report ascribes the large decline in emissions to three factors that had roughly equivalent impacts: the decline in the GDP, a less energy-intensive economy, and a less carbon-intensive energy supply.

But the real news is that for roughly the past decade the the relationship between GDP and emission levels seems to have broken down:

The DOE report, compiled by its Energy Information Administration, provides both a retrospective analysis of the past few decades, and a breakdown of the factors contributing to the most recent year’s decline. But both of them point in roughly the same direction: the relationship between economic growth and carbon emissions that held in the 1990s no longer exists. In that decade, carbon emissions grew at about half the rate of the US GDP. In the more recent decade, GDP growth dropped by half, but carbon emissions actually declined over the course of the decade—by an average of nearly one percent annually…

Residential and commercial energy use have remained pretty flat for the last three years, but transportation started a gradual decline in energy consumption in 2007. Although 2008 saw a huge decline in driving due to fuel prices, the cost of fuel dropped in 2009. As one might expect, total miles traveled rose, although only by a small fraction of a percent. Nevertheless, total fuel consumption was down from 2008 for every month of the year, spurred in part by an increase of 1.5mpg in the average fleet fuel economy. Given that the fuel economy is set to rise rapidly through 2016, this sector is likely to continue to improve.

But the big change in the energy intensity (energy burned per unit of GDP) came from the industrial sector, which has been declining since 2004. The report ascribes this to the rapid growth of the electronics industry, which is less energy intensive than industries like the production of primary metals, and therefore has a lower carbon intensity. A growth in the service economy also contributed. The industrial sector is still the largest consumer of energy in the US, with transportation now a close second.

The electric power sector became greener still, seeing a drop in carbon intensity of four percent (compared to about three percent for industrial). In fact, the drop in carbon emissions from the electric sector accounted for over half of the total national decline. The biggest contributor here was the fall in coal use, which went down by several percent. That was offset by increases in natural gas, renewables, and nuclear power.

The fall in natural gas prices that has helped drive the shift away from coal has also ensured that the plants that are now coming online are much more efficient. As a result, the amount of power generated per unit of carbon emissions has been climbing steadily over the last decade. The rise in nuclear power came despite the fact that no new plants have been built in decades; we’re simply better at extracting more power from existing facilities. But the biggest change came from the boom in wind power. In 2009, wind produced 71 billion kWhrs of electricity, up from only 6 billion at the start of the decade.

Again, these are trends that seem likely to continue. The current administration is pushing for licensing and approval of both renewable and nuclear generating capacity, and many states have renewable power mandates on the books. So, for the next few years at least, it’s likely that the carbon intensity of the electrical power sector will continue to drop.

This relationship is something that I have mentioned before. Many people who complain about the fact that the economy is on a path of endless grow worry about what that means for the environment. But the relationship between the environmental impact of the economy and the size of the economy isn’t set in stone. It can change, as the past decade’s emissions demonstrate. At least for a narrow measure of environmental impact.

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