US energy sector emissions increased slightly in 2013, according to new data from the Energy Information Administration (EIA). This may seem like bad news for President Obama, who has pledged to cut the country’s emissions 17 per cent by 2020.

Obama unveiled his clean power plan earlier this year to much fanfare. The centrepiece of the plan is to reduce emissions from electricity generation by 30 per cent by 2020.

The US’s rising energy sector emissions seem to suggest the policy may not be as effective as Obama hopes.

Obama’s clean power plan specifically targets emissions from power generation, which accounts for  about 32 per cent of the US’s total emissions. Cutting emissions from the US’s homes and businesses is a much smaller part of his wider  Climate Action Plan.

The EIA’s data shows the potential limitations of focusing on cutting power generation emissions without addressing the country’s broader energy consumption.

Emissions increase

US energy sector emissions increased 2.5 per cent in 2013 compared to year before, the EIA’s data shows. The EIA says the main reason for the increase was colder weather.

Winter temperatures at the start of 2013 were lower than a year before, and the US also experienced a particularly mild spring last year. Temperatures fell again later in the year, when the US was engulfed by the polar vortex.

Source: National Oceanic and Atmospheric Administration, average monthly temperatures. Graph by Carbon Brief.

Households and businesses turned up their thermostats in response to the lower temperatures, which meant burning a lot more gas and a bit more oil. The residential sector was responsible for 48 per cent of 2013’s emissions increase, mostly due to heat demand, the EIA says.

The cold weather was also partially responsible for emissions from electricity generation rising in 2013. About a third of US homes have electric heating, and residential electricity demand rose about one per cent in 2013.

But the US’s power mix also became slightly more polluting, and that wasn’t down to the weather.

US gas prices rose in 2013, which made coal more economically attractive. As a consequence, gas generation fell significantly – about 10 per cent compared to a year before – and was largely replaced with coal power, as this graph shows:

Changes in power generation, 2012 to 2013. Source: US Energy Information Administration, US Energy-Related Carbon Dioxide Emissions 2013. Graph by Carbon Brief.

An increase in wind, solar and nuclear generation dampened the impact of switching from gas to coal slightly. But the carbon intensity of the US’s power sector – the emissions associated with each megawatt of electricity power plants produce – rose 0.6 per cent in 2013.

Overall, emissions from electricity generation rose 0.8 per cent.

Long-term trend

While 2013’s energy sector emissions were higher than 2012’s, they were still considerably lower than 2007’s peak. US power sector emissions have also generally fallen over the last eight years.

Renewable electricity generation has grown significantly in the US in the past decade, providing 46 per cent more power in 2013 than in 2005. The US’s shale gas boom has also helped curb emissions by decreasing demand for coal.

This chart shows how much the US’s emissions have been curbed by switching to natural gas (the grey bars), and renewables and nuclear (the blue bars):

Changes in power generation, 2012 to 2013. Source: US Energy Information Administration, US Energy-Related Carbon Dioxide Emissions 2013. Graph by Carbon Brief.

The EIA says this fuel switching has prevented US power plants emitting over a billion tonnes of carbon dioxide since 2005.

Power sector emissions are going to have to keep falling if the US is going hit Obama’s emissions reduction goals, as the graph below shows.  Power sector emissions are currently 16 per cent lower than they were in 2005. Obama has pledged to make them 30 per cent lower by 2020.

Source: US Energy Information Administration, US Energy-Related Carbon Dioxide Emissions 2013. Graph and projections by Carbon Brief.

So 2013’s slight emissions increase might only be a blip. The EIA seems to think it is. The “specific circumstances” of expensive gas and unusually cold weather may not repeat themselves in 2014, it says.

Early indications aren’t promising, however. The EIA has data running up to June this year which shows fossil fuel use has increased compared to the first six months of 2013, although so has the amount of electricity generated by renewables.

Whether the US’s energy sector emissions rise or fall in 2014 is likely to be down to the weather, again. So while Obama’s clean power plan may have some impact on emissions from power generation, the US needs to do more to improve the energy efficiency of its homes and buildings if it wants the whole energy sector’s emissions to follow suit.