Expert Voices

Carbon-Dioxide Emissions Falling, But Is That Enough?

Offshore Wind Farm Could Blow Away Energy Need

Dan Lashof, director of NRDC’s Climate and Clean Air Program, contributed this article to LiveScience’s Expert Voices: Op-Ed & Insights.

The official U.S. energy-data keeper, the Energy Information Administration (EIA), recently released full-year data for 2012 that show a nearly 4 percent reduction in carbon-dioxide emissions from fossil-fuel combustion compared to 2011 levels. 

The findings from the report show U.S. carbon-dioxide emissions were at a level 12 percent below the level seen in 2005, a year that serves as the benchmark for President Obama's commitment to reduce global warming (a reduction of 17 percent below 2005 levels by the year 2020).

By now, many commentators have noted that low natural-gas prices have reduced power-plant pollution as gas-fired generation has replaced higher-emitting coal-fired power. Indeed, in April 2012, generation from natural gas equaled generation from coal for the first time since EIA started keeping track in 1973. For the year as a whole, coal supplied less than 40 percent of U.S. electricity, and natural gas supplied more than 30 percent for the first time since EIA began keeping records.

Replacing coal with natural gas reduces smokestack emissions of carbon dioxide, sulfur dioxide and mercury, but natural-gas production and distribution come with a host of problems, including methane leaks, contaminated water supplies, destroyed streams and devastated landscapes. And while gas-fired power plants have lower carbon-dioxide emissions than coal-fired ones, their emissions are still far too high to be considered a global-warming solution. Fortunately, there is a lot more behind the decline in U.S. carbon-dioxide emissions.

Sticking with the power sector for the moment, energy efficiency has played a crucial role in lowering carbon-dioxide emissions. EIA’s data show that total electricity generation in 2012 was more than 1 percent lower than in 2011 and virtually identical to 2005 levels. Meanwhile, the real (inflation-adjusted) gross domestic product grew by more than 2 percent last year and was nearly 8 percent higher than in 2005.

At the same time, there was a significant increase in renewable energy generation, particularly from wind, which produced 3.5 percent of total net generation in 2012, compared with less than 3 percent in 2011 and less than 0.5 percent in 2005.

Emissions from vehicles are also declining. Overall carbon-dioxide emissions from oil burning for transportation fell by more than 2 percent in 2012 compared to 2011 and were just more than 9 percent below 2005 levels. While the amounts varied, there were reductions from each of the major contributors: gasoline, diesel and jet fuel. Those reductions are due to a combination of increases in vehicle efficiency and reductions in driving. U.S. Environmental Protection Agency data show that carbon-dioxide emissions from new passenger vehicles fell to 374 grams per mile (13.9 ounces per mile) in 2012 — a 6 percent reduction since 2011 and a remarkable 16 percent reduction since 2005.

Of course, the efficiency of the vehicle fleet as a whole lags behind the new car levels. My colleague Luke Tonachel estimates that the fleet-wide carbon-dioxide emissions rate has declined by about 3 percent since 2005, while total driving has declined slightly. In addition, EIA data show that ethanol use has increased from just more than 1 percent to more than 4 percent of transportation energy consumption. (EIA treats ethanol combustion as if it were carbon neutral, even though the life-cycle emissions from producing and using ethanol can be higher than those from gasoline.)

Another perspective on the carbon-dioxide emissions reduction comes from comparing what actually happened in 2012 to a scenario that considers the effects from a recession, a shift in energy sources or improvements in energy efficiency. The Council of Economic Advisors performed such an analysis, which is included in the 2013 Economic Report of the President. 

That analysis found that 2012 carbon-dioxide emissions were 17 percent below the business-as-usual baseline constructed by the council (as opposed to 12 percent below actual 2005 emissions). The council concluded that 52 percent of the reduction was due to the recession, 40 percent was due to cleaner fuels and 8 percent was due to accelerated improvements in energy efficiency. Note that this decomposition significantly understates the overall role of energy efficiency because the council only counted the acceleration of energy-efficiency improvements relative to their business-as-usual forecast, which already assumed that energy use per dollar of gross domestic product would fall by just more than 1.5 percent per year.

Of course, the most important remaining question is, can the United States continue to reduce its carbon-dioxide emissions in the future to achieve the president’s 2020 goal and, eventually, the 80 percent or greater reduction needed to prevent the most dangerous risks of climate disruption? [Worst Allergy Season Ever?]

As I have noted before, this target is within reach, but additional policies — particularly power-plant carbon-pollution standards — will be needed. The president’s science advisers have presented a great six-point plan for achieving this goal.

However, in the near term, don’t be surprised if carbon-dioxide emissions increase this year. EIA’s Short-Term Energy Outlook forecasts almost a 2 percent jump in carbon-dioxide emissions, mostly from increased coal combustion as natural-gas prices rise.

To prevent that increase from occurring, and to sustain the rate of progress we have seen in recent years, we will need to redouble clean-energy efforts at all levels: federal carbon and energy-efficiency standards; state renewable energy, energy efficiency and transportation policies; and local organizing by citizens to replace dirty coal plants with clean alternatives.

We can build the clean energy future we need, but we aren’t there yet — and it’s not going to happen by itself.

The views expressed are those of the author and do not necessarily reflect the views of the publisher.

Natural Resources Defense Council