Coal to natural gas study: The critical detail you might have missed

A recent study suggests replacing 50 percent of coal use with natural gas might actually make climate change worse over the short term. It's a stunning conclusion that would appear to debunk the often-touted benefits of natural gas and give renewable energy a considerable boost. But that's hardly the whole story.

Unfortunately, in a rush to report the news, much of the media coverage has missed or failed to highlight an important detail. The study, conducted by Tom Wigley with the National Center for Atmospheric Research, used computer simulations to project that the amount of methane leakage from gas wells during production -- which will increase as natural gas replaces coal-fired power plants -- will cause global temperatures to rise over the next 40 years.

Burning less coal would reduce carbon dioxide emissions. However, the computer simulations used in the study focused on the impact of methane leaked from natural gas wells during the production process. To be clear, there's considerable debate about how much methane actually leaks into the atmosphere during unconventional natural gas production. But it's concern because methane is a greenhouse gas emission more powerful than carbon dioxide.

The study included a graph [via UCAR] that shows a link between future high temperatures and the amount of methane leaked.

So, the natural conclusion would be that natural gas will cause global temps to rise. Blogger Robert Rapier astutely noted that the media missed an important piece of the study:

Notice that the projected temperature increases in every case -- even when there is no methane leakage. That indicates that something else is going on here.

Indeed. So why the heck do the computer simulations show rising temps even when there's zero methane leakage? Two words: sulfur dioxide. Rapier again explains:

Coal has higher particulate emissions that increase air pollution, but they help reflect the sun away from the earth.

In other words, the nasty air pollution that turns the Shanghai skyline into a hazy mirage and creates acid rain, also has a cooling effect. (See Shanghai below, and the coal barges in the foreground). It's a point that only a few outlets, such as MIT's Technology Review, highlighted in their coverage of the study.

Upon this discovery, Rapier took the next logical step and called the study's author to ask if based on the computer models, did this mean that temperatures would rise over the short term even if the world replaced coal with a zero emissions source of electricity like solar or wind?

The answer? Yes.

This doesn't mean we shouldn't replace coal with cleaner fuel sources. To the contrary, the air pollution coal produces has a direct impact on public health. Nor is this an attempt to support natural gas. Natural gas justifiably has its fair share of detractors and hydraulic fracturing, a technique used to unlock gas trapped in shale, is hardly innocuous.

This does show the complexity of dealing with climate change. And it illustrates the problem with the coal versus natural gas debate and how quickly studies can be spun accidentally or even purposefully to suit a particular viewpoint.

For example, a paper released this year from Cornell University received quite a bit of coverage after declaring that natural gas produced from shale is dirtier than coal.  For folks concerned about the impact of hydraulic fracturing, the study was a confirmation of their fears and provided a pretty strong argument against the drilling method.

As I wrote at the time, natural gas is far from the wonder fuel its supporters claim it to be. But the Cornell study can't be taken seriously because of inadequate data and a serious methodological problem. Which is to not say it's wrong, just that we have no real way of knowing. And in fact, the lack of available data was something even the author readily admitted to.

Photo: Flickr users, stevendepolo; pedronet

This post was originally published on Smartplanet.com