Ken Caldeira: We had a paper come out comparing effects of natural gas versus coal plants, aimed at understanding how much methane leakage there could be from natural gas before it caused more near-term warming than coal.
The answer depends on how efficient the different power plants are, but one thing that is clear is that natural gas plants contribute substantially to global warming, making me skeptical about claims that expanding our natural gas infrastructure is really a path to a near-zero emission energy future.
Key factors for assessing climate benefits of natural gas versus coal electricity generation
Assessing potential climate effects of natural gas versus coal electricity generation is complicated by the large number of factors reported in life cycle assessment studies, compounded by the large number of proposed climate metrics. Thus, there is a need to identify the key factors affecting the climate effects of natural gas versus coal electricity production, and to present these climate effects in as clear and transparent a way as possible.
Here, we identify power plant efficiencies and methane leakage rates as the factors that explain most of the variance in greenhouse gas emissions by natural gas and coal power plants. Thus, we focus on the role of these factors in determining the relative merits of natural gas versus coal power plants.
We develop a simple model estimating CO2 and CH4 emissions from natural gas and coal power plants, and resulting temperature change. Simple underlying physical changes can be obscured by abstract evaluation metrics, thus we focus our analysis on the time evolution of global mean temperature.
We find that, during the period of plant operation, if there is substantial methane leakage, natural gas plants can produce greater near-term warming than coal plants with the same power output. However, if methane leakage rates are low and power plant efficiency is high, natural gas plants can produce some reduction in near-term warming. In the long term, natural gas power plants produce less warming than would occur with coal power plants.
However, without carbon capture and storage natural gas power plants cannot achieve the deep reductions that would be required to avoid substantial contribution to additional global warming.
Read the open access study at http://iopscience.iop.org/1748-9326/9/11/114022/article