Climatic Change 108, 601–608 (2011)

Credit: © ISTOCKPHOTO.COM/TWILIGHT EYE

Coal, as every environmentalist knows, is the filthy fuel. However, a new study by Tom Wigley of the US National Center for Atmospheric Research in Boulder, Colorado, USA, finds that even though natural gas produces only half of the carbon dioxide of coal per unit of energy, a world where gas replaced coal would actually be warmer for many decades.

Some of the aerosols produced from coal combustion have a cooling effect and this, combined with the tendency of natural gas to leak out into the atmosphere — methane is a potent greenhouse gas — overrides the gains from smaller carbon dioxide emissions.

Wigley reports that unless methane leakage rates can be kept below 2%, completely substituting natural-gas power generators for coal ones will not reduce global warming. With no leakage at all, this change would still cause additional warming until 2050; with 10% methane leakage, Earth will get hotter than it otherwise would until 2140.