It looks like good news, but it's not. The US has recorded a sharp fall in its greenhouse gas emissions from energy use. Thanks to a rise in the use of natural gas, emissions are at their lowest since 1992. The fall will boost the natural gas industry, but in reality the emissions have simply been exported.
According to the US Energy Information Agency (EIA), energy-related CO2 emissions in the first quarter of 2012 were the lowest in two decades. Emissions are normally high between January and March because people use more heating in the winter, but last winter was mild in the US.
The EIA says that an increase in gas-fired power generation, and a corresponding decline in coal-fired, contributed to the fall in emissions. Burning natural gas produces fewer emissions than burning coal, and natural gas is currently unusually cheap in the US thanks to a glut of shale gas extracted by hydraulic fracturing or "fracking".
If gas companies continue to expand their shale gas operations, the US could generate even more electricity from gas, and its emissions could fall for several years, says Kevin Anderson of the University of Manchester, UK.
However, this will not slow down climate change. US coal consumption has fallen, but production is holding steady and the surplus is being sold to Asia. As a result, the US is effectively exporting the coal-related emissions.
"Gas is less bad than burning the coal, but only if you keep the coal in the ground," Anderson says.
Proponents of natural gas argue that it is a "transition fuel" that we can burn for a few years while we install low-carbon infrastructure such as wind farms and nuclear power stations.
That viewpoint looks increasingly untenable. "If we want even an outside chance of [limiting global warming to] 2 °C, there is no emission space for gas," Anderson says. In order to hit the 2 °C target, global emissions need to peak by 2020 before dropping again, which means making a rapid transition to low-carbon energy.
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