Coal combustion releases more carbon dioxide than other fossil fuels, as well as high levels of other pollutants called sulfur dioxide, nitrogen oxides, and solid particles. Will greater usage of natural gas slow down global warming and reduce the impacts of energy use on the environment? The effects of natural gas on climate change have been difficult to characterize and recent studies have come to conflicting conclusions. There is uncertainty about the extent of methane leakage from old and new wells, and from processing and pipelining.
A new study by Tom Wigley, National Center for Atmospheric Research, takes a comprehensive look at the issue by incorporating the cooling effects of sulfur particles associated with coal burning and by analyzing the complex climatic influences of methane, which affects other atmospheric gases such as ozone and water vapor. Computer simulations have found that a 50 percent reduction in coal and a corresponding increase in natural gas use would lead to a slight increase in worldwide warming for the next 40 years of about 0.1 degree Fahrenheit (less than 0.1 degree Celsius). The reliance on natural gas could then gradually reduce the rate of global warming, but temperatures would drop by only a small amount compared to the 5.4 degrees F (3 degrees C) of warming projected by 2100 under current energy trends.
If the rate of methane leaks from natural gas could be held to around 2 percent, for example, the study indicates that warming would be reduced by less than 0.2 degrees F (about 0.1 degree C) by 2100. The reduction in warming would be more pronounced with zero leakage, which would result in a reduction of warming by 2100 of about 0.2-0.3 degrees F (0.1-0.2 degrees C). However, a high leak rate of 10 percent would mean that global warming would not be reduced until 2140.
Whatever the methane leakage rate, you can’t get away from the additional warming that will occur initially because, by not burning coal, you’re not having the cooling effect of sulfates and other particles. This particle effect is a double-edged sword because reducing them is a good thing in terms of lessening air pollution and acid rain. But the paradox is when we clean up these particles, it slows down efforts to reduce global warming.
In summary, the results show that the substitution of gas for coal as an energy source results in increased rather than decreased global warming for many decades — out to the mid 22nd century for the 10% leakage case.
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