Replacing coal gives you other benefits as well, such as reducing the sulfate pollution that causes acid rain, particulate emissions that cause lung disease, and mercury that causes brain damage. And if less coal is mined, then occupational death and disease can be reduced in coal miners and the destruction caused by damaging forms of mining, including the removal, in some parts of the country, of entire mountains can be reduced or halted.
Those are significant benefits. In part for these reasons, the Obama administration has made natural gas development a centerpiece of its energy policy, and environmental groups, including the Environmental Defense Fund, have supported the increased use of gas. President Obama has gone as far as to endorse fracking—the controversial method of extracting natural gas from low permeability shales—on the grounds that the gas extracted can provide "a bridge" to a low carbon future and help fight climate change.
So if someone asks: "Is gas better than oil or coal?" the short answer seems to be yes. And when it comes to complicated issues that have science at their core, often the short answer is the (basically) correct one.
As a historian of science who studies global warming, I've often stressed that anthropogenic climate change is a matter of basic physics: CO2 is a greenhouse gas, which means it traps heat in the Earth's atmosphere. So if you put additional CO2 into that atmosphere, above and beyond what's naturally there, you have to expect the planet to warm. Basic physics.
And guess what? We've added a substantial amount of CO2 to the atmosphere, and the planet has become hotter. We can fuss about the details of natural variability, cloud feedbacks, ocean heat and CO2 uptake, El Niño cycles and the like, but the answer that you get from college-level physics—more CO2 means a hotter planet—has turned out to be correct. The details may affect the timing and mode of climate warming, but they won't stop it.
In the case of gas, however, the short answer may not be the correct one.
The often-touted decrease in greenhouse gas production applies when natural gas replaces other fuels—particularly coal—in electricity generation. That's important. Electricity is about 40% of total US energy use. Traditionally, coal has been the dominant fuel used to generate electricity in this country and most of the world. (And no one has any serious plan to live without electricity.) Any measurable GHG reduction in the electricity sector is significant and gains achieved in that sector quickly add up.
But a good deal of the benefit of gas in electricity generation comes from the fact that it is used in modern combined-cycle gas turbine plants. A combined-cycle plant is one in which waste heat is captured and redirected to drive a mechanical system that powers a generator that creates additional electricity. These plants can be nearly twice as efficient as conventional single-cycle plants. In addition, if combined with cogeneration (the trapping of the last bits of heat for local home heating or other purposes), they can reach efficiencies of nearly 90%. That means that nearly all the heat released by burning the fuel is captured and used—an impressive accomplishment.
In theory, you could build a combined-cycle plant with coal (or other fuels), but it's not often done. You can also increase coal efficiency by pulverizing it, and using a technique called "ultra super-critical black coal." An expert report compiled by the Australian Council of Learned Societies in 2013 compared the efficiencies of a range of fuels, including conventional gas and shale gas, under a variety of conditions, and concluded that greenhouse gas emissions from electricity generation using efficient forms of coal burning were not that much more than from gas.
What this means is that most of the benefit natural gas offers comes not from the gas itself, but from how it is burned, and this is mostly because gas plants tend to be new and use more efficient burning technologies. The lesson, not surprisingly: if you burn a fuel using twenty-first century technology, you get a better result than with late nineteenth or twentieth century technology. This is not to defend coal, but to provide an important reality check on the discussion now taking place in this country. There is a real benefit to burning gas in America, but it's less than often claimed, and much of that benefit comes from using modern techniques and new equipment. (If the coal industry weren't so busy denying the reality of climate change, they might publicize this fact.)
It's Not Just Electricity
Replacing coal with gas in electricity generation is still probably a good idea—at least in the near term—but gas isn't just used to generate electricity. It's also used in transportation, to heat homes and make hot water, and in gas appliances like stoves, driers, and fireplaces. Here the situation is seriously worrisome.
It's extremely difficult to estimate GHG emissions in these sectors because many of the variables are poorly measured. One important emission source is gas leakage from distribution and storage systems, which is hard to measure because it happens in so many different ways in so many different places. Such leaks are sometimes called "downstream emissions," because they occur after the gas has been drilled.
Certainly, gas does leak, and the more we transport, distribute, and use it, the more opportunities there are for such leakage. Studies have tried to estimate the total emissions associated with gas using well-to-burner or "life-cycle" analysis. Different studies of this sort tend to yield quite different results with a high margin for error, but many conclude that when natural gas replaces petroleum in transportation or heating oil in homes, the greenhouse gas benefits are slim to none. (And since almost no one in America heats their home with coal any more, there are no ancillary benefits of decreased coal.) One study by researchers at Carnegie-Mellon University concluded that while the probability of reducing GHG emissions at least somewhat by replacing coal with gas in electricity generation was 100%, the substitution of natural gas as a transportation fuel actually carries a 10%-35% risk of increasing emissions.
In the Northeast, the northern Midwest, and the Great Plains, many builders are touting the "energy efficiency" of new homes supplied with gas heat and hot water systems, but it's not clear that these homes are achieving substantial GHG reductions. In New England, where wood is plentiful, many people would do better to use high efficiency wood stoves (or burn other forms of biomass).
How Gas (CH4) Heats the Atmosphere Much More than CO2
Isn't gas still better than oil for heating homes? Perhaps, but oil doesn't leak into the atmosphere, which brings us to a crucial point: natural gas is methane (CH4), which is a greenhouse gas far more potent than CO2.
As a result, gas leaks are a cause for enormous concern, because any methane that reaches the atmosphere unburned contributes to global warming more than the same amount of CO2. How much more? This is a question that has caused considerable angst in the climate science community, because it depends on how you calculate it. Scientists have developed the concept of "Global Warming Potential" (GWP) to try to answer this question.
The argument is complicated because while CH4 warms the planet far more than CO2, it stays in the atmosphere for much less time. A typical molecule of CO2 remains in the atmosphere about 10 times longer than a molecule of CH4. In their Fifth Assessment Report, the Intergovernmental Panel on Climate Change estimated that the GWP for methane is 34 times that of CO2 over the span of 100 years. However, when the time frame is changed to 20 years, the GWP increases to 86!
Most calculations of the impact of methane leakage use the 100-year time frame, which makes sense if you are worried about the cumulative impact of greenhouse gas emissions on the world as a whole, but not—many scientists have started to argue—if you are worried about currently unfolding impacts on the biosphere. After all, many species may go extinct well before we reach that 100-year mark. It also does not make sense if you are worried that we are quickly approaching irreversible tipping points in the climate system, including rapid ice loss from the Greenland and Antarctic ice sheets.
It gets worse. CH4 and CO2 are not the only components of air pollution that can alter the climate. Dust particles from pollution or volcanoes have the capacity to cool the climate. As it happens, burning coal produces a lot of dust, leading some scientists to conclude that replacing coal with natural gas may actually increase global warming. If they are right, then not only is natural gas not a bridge to a clean energy future, it's a bridge to potential disaster.
A great deal of recent public and media attention has been focused not on gas itself, but on the mechanism increasingly used to extract it. Hydraulic fracturing—better known as fracking—is a technique that uses high-pressure fluids to "fracture" and extract gas from low permeability rocks where it would otherwise be trapped. The technique itself has been around for a long time, but in the last decade, combined with innovations in drilling technology and the high cost of petroleum, it has become a profitable way to produce energy.
The somewhat surprising result of several recent studies (including one by an expert panel from the Council of Canadian Academies on which I served) is that, from a climate-change perspective, fracking probably isn't much worse than conventional gas extraction. Life-cycle analyses of GHG emissions from the Marcellus and Bakken shales, for example, suggest that emissions are probably slightly but not significantly higher than from conventional gas drilling. A good proportion of these emissions come from well leakage.
It turns out to be surprisingly hard to seal a well tightly. This is widely acknowledged even by industry representatives and shale gas advocates. They call it the problem of "well integrity." Wells may leak when they are being drilled, during production, and even when abandoned after production has ended. The reason is primarily because the cement used to seal the well may shrink, crack, or simply fail to fill in all the gaps.
Interestingly, there's little evidence that fracked wells leak more than conventional wells. From a greenhouse gas perspective, the problem with fracking lies in the huge number of wells being drilled. According to the US Energy Information Administration, there were 342,000 gas wells in the United States in 2000; by 2010, there were over 510,000, and nearly all of this increase was driven by shale-gas development—that is, by fracking. This represents a huge increase in the potential pathways for methane leakage directly into the atmosphere. (It also represents a huge increase in potential sources of groundwater contamination, but that's a subject for another post.)
There have been enormous disagreements among scientists and industry representatives over methane leakage rates, but experts calculate that leakage must be kept below 3% for gas to represent an improvement over coal in electricity generation, and below 1% for gas to improve over diesel and gasoline in transportation. The Environmental Protection Agency (EPA) currently estimates average leakage rates at 1.4%, but quite a few experts dispute that figure. One study published in 2013, based on atmospheric measurements over gas fields in Utah, found leakage rates as high as 6%-11%. The Environmental Defense Fund is currently sponsoring a large, collaborative project involving diverse industry, government, and academic scientists. One part of the study, measuring emissions over Colorado's most active oil and gas drilling region, found methane emissions almost three times higher than the EPA's 2012 numbers, corresponding to a well-leakage rate of 2.6%-5.6%.
Some of the differences in leakage estimates reflect differing measurement techniques, some may involve measurement error, and some probably reflect real differences in gas fields and industrial practices. But the range of estimates indicates that the scientific jury is still out. If, in the end, leakage rates prove to be higher than the EPA currently calculates, the promised benefits of gas begin to vaporize. If leakage in storage and distribution is higher than currently estimated—as one ongoing study by my own colleagues at Harvard suggests—then the alleged benefits may evaporate entirely.
And we're not done yet. There's one more important pathway to consider when it comes to the release of greenhouse gases into the atmosphere: flaring. In this practice, gas is burned off at the wellhead, sending carbon dioxide into the atmosphere. It's most commonly done in oil fields. There, natural gas is not a desirable product but a hazardous byproduct that companies flare to avoid gas explosions. (If you fly over the Persian Gulf at night and notice numerous points of light below, those are wellhead fires).
In our report for the Council of Canadian Academies, our panel relied on industry data that suggested flaring rates in gas fields were extremely low, typically less than 2% and "in all probability" less than 0.1%. This would make sense if gas producers were efficient, since they want to sell gas, not flare it. But recently the Wall Street Journal reported that state officials in North Dakota would be pressing for new regulations because flaring rates there are running around 30%. In the month of April alone, $50 million dollars of natural gas was burned off, completely wasted. The article was discussing shale oil wells, not shale gas ones, but it suggests that, when it comes to controlling flaring, there's evidence the store is not being adequately minded. (At present, there are no federal regulations at all on flaring.) As long as gas is cheap, the economic incentives to avoid waste are obviously insufficient.
Why Gas is Unlikely To Be a Bridge to Renewables
In a perfect world, people would use gas to replace more polluting coal or oil. Unfortunately, the argument for gas rests on just that assumption: that the world works perfectly. You don't need to be a scientist, however, to know just how flawed that assumption is. In fact, economists have long argued that a paradox of energy efficiency is this: if people save energy through efficiency and their energy bills start to fall, they may begin to use more energy in other ways. So while their bills stay the same, usage may actually rise. (It's like going to a sale and instead of saving money, buying more things because of the lower price tags.) In this way, consumers can actually end up using more energy overall and so emissions continue to rise.
To ensure that natural gas use doesn't follow such a path, you've got to do something. You could introduce a law, like AB32, the California emissions control law, or put in place the pending EPA carbon rule just introduced by the Obama administration that mandates emissions reductions. Or you could introduce a hefty carbon tax to create a strong financial incentive for people to choose non-carbon based fuels. But laws like AB32 are at present few and far between, the fossil fuel industry and its political and ideological allies are fighting the EPA carbon rule tooth and nail, and only a handful of political leaders are prepared to stand up in public and argue for a new tax.
Meanwhile, global fossil fuel production and consumption are rising. A recent article by the business editor of the British Telegraph describes a frenzy of fossil fuel production that may be leading to a new financial bubble. The huge increase in natural gas production is, in reality, helping to keep the price of such energy lower, discouraging efficiency and making it more difficult for renewables to compete. And this raises the most worrisome issue of all.
Embedded in all positive claims for gas is an essential assumption: that it replaces other more polluting fuels. But what if it also turns out to replace the panoply of alternative energies, including solar, wind, hydro, and nuclear? In Canada, where shale-gas development is well advanced, only a small fraction of electricity is generated from coal; most comes from hydropower or nuclear power. In the US, competition from cheap gas was recently cited by the owners of the Vermont Yankee Nuclear power plant as a factor in their decision to close down. And while the evidence may be somewhat anecdotal, various reports suggest that cheap gas has delayed or halted some renewable power projects. It stands to reason that if people believe natural gas is a "green" alternative, they will chose it over more expensive renewables.
Exports and Infrastructure: The Road to More Climate Change
We've all heard about the Keystone XL Pipeline through which Canada proposes to ship oil from the Alberta tar sands to the US Gulf Coast, and from there to the rest of the world. Few people, however, are aware that the US has also become a net exporter of coal and is poised to become a gas exporter as well. Gas imports have fallen steadily since 2007, while exports have risen, and several US gas companies are actively seeking federal and state approvals for the building of expanded gas export facilities.
Once coal leaves our borders, the argument for replacing it becomes moot because there's no way for us to monitor how it's used. If gas replaces coal in the US and that coal is then exported and burned elsewhere, then there's no greenhouse gas benefit at all. Meanwhile, the negative effects of coal have been passed on to others.
All of the available scientific evidence suggests that greenhouse gas emissions must peak relatively soon and then fall dramatically over the next 50 years, if not sooner, if we are to avoid the most damaging and disruptive aspects of climate change. Yet we are building, or contemplating building, pipelines and export facilities that will contribute to increased fossil fuel use around the globe, ensuring further increases in emissions during the crucial period when they need to be dramatically decreasing.
We are also building new power plants that will be with us for a long time. (A typical power plant is expected to operate for at least 50 years.) Once technologies are adopted and infrastructure built to support them, it becomes difficult and expensive to change course. Historians of technology call this "technological momentum."
Certain forms of infrastructure also effectively preclude others. Once you have built a city, you can't use the same land for agriculture. Historians call this the "infrastructure trap." The aggressive development of natural gas, not to mention tar sands, and oil in the melting Arctic, threaten to trap us into a commitment to fossil fuels that may be impossible to escape before it is too late. Animals are lured into traps by the promise of food. Is the idea of short-term cuts in greenhouse gas emissions luring us into the trap of long-term failure?
The institution of rules or incentives in the US and around the globe to ensure that gas actually replaces coal and that efficiency and renewables become our primary focus for energy development is at this point extremely unlikely. Yet without them, increased natural gas development will simply increase the total amount of fossil fuel available in the world to burn, accelerating what is already beginning to look like a rush towards disaster.
Have US Emissions Really Decreased?
Gas advocates say that while these worries might be legitimate, US greenhouse gas emissions nonetheless fell between 2008 and 2012, partly because of the way gas is replacing coal in electricity generation. This claim needs to be closely examined. In fact, it seems as if the lion's share of that decrease was simply the result of the near global economic meltdown of 2007-2008 and the Great Recession that followed. When economic activity falls, energy use falls, so emissions fall, too. Not surprisingly, preliminary data from 2013 suggest that emissions are on the rise again. Some of the rest of the 2008-2012 decline was due to tighter automobile fuel economy standards.
But how do we know what our emissions actually are? Most people would assume that we measure them, but they would be wrong. Emissions are instead calculated based on energy data—how much coal, oil, and gas was bought and sold in the US that year—multiplied by assumed rates of greenhouse gas production by those fuels. Here's the rub: the gas calculation depends on the assumed leakage rate. If we've been underestimating leakage, then we've underestimated the emissions. Though the converse is also true, few experts think that anyone is overestimating gas leakage rates. This is not to say that emissions didn't fall in 2008-2012. They almost certainly did, again because of the recession. But the claim that there's been a large decrease thanks to natural gas remains unproven.
So Why Are So Many People So Enthusiastic About Gas?
The reason for industry enthusiasm isn't hard to discern: a lot of people are making a lot of money right now in shale gas. Chalk up the enthusiasm of the Canadian government, politicians in gas-rich states like Texas, North Dakota, and Pennsylvania, and individuals who have made money leasing their properties for gas drilling to the same factor. In those gas-rich states, employment, too, has benefited (even as the familiar social problems characteristic of boom towns have also increased).
On natural gas, the Obama administration seems to be looking for a compromise that Democrats and Republicans can support, and that does not invoke the wrath of the powerful and aggressive oil and gas industry or voters in states like Pennsylvania. In the process, it's surely tempting to demonize the coal industry, with its long history of abusive labor practices, its callous disregard for occupational health, and its catastrophic environmental record. Since few of us ever see coal in our daily lives, a future without coal seems not only imaginable but overdue.
But when it comes to natural gas, what about the enthusiasm of some environmentalists? What about groups like the Environmental Defense Fund that have a long track record on climate change and no history of love for the oil and gas industry? What about scientists?
In such cases, I think the positive response to the exploitation of natural gas lies in a combination of wishful thinking and intimidation.
The fossil fuel industry and their allies have spent the past 20 years attacking environmentalists and climate scientists as extremists, alarmists, and hysterics. Their publicists have portrayed them as hair-shirt wearing, socialist watermelons (green on the outside, red on the inside) who relish suffering, kill jobs, and want everyone to freeze in the dark. Extremists do exist in the environmental movement as everywhere else, but they represent a tiny faction of the community of people concerned about climate change, and they are virtually nonexistent in the scientific community. (Put it this way: if there is a hair-shirt wearing climate scientist, I have not met her.)
While the accusations may be false, that doesn't mean they don't affect our thinking. Too often, environmentalists find ourselves trying to prove that we are not what they say we are: not irredeemable anti-business job-killers. We bend over backwards to seek out acceptable compromises and work with business leaders, even to the point of finding a fossil fuel that we can love (or at least like).
And that leads to the wishful thinking. We want to find solutions, or at least meaningful steps in the right direction, that command widespread support. We want gas to be good. (I know I did.) Climate change is a gargantuan challenge, and it's bloody hard to see how we are going to solve it and maintain our standard of living, much less extend that standard to billions more around the globe who want it and deserve it. If gas is good, or at least better than what we have now—then that feels like a good thing. If gas moved us substantially in the right direction, then that would be a good thing.
After all, can't the leakage problem be fixed? Our panel spent considerable time discussing this question. Industry representatives said, "Trust us, we've been drilling wells for 100 years." But some of us wondered, "If they haven't solved this problem in 100 years, why would they suddenly solve it now?" A strong system of monitoring and compliance enforcement could help create incentives for industry to find a solution, but the odds of that developing any time soon seem as remote as the odds of a binding international treaty.
Sometimes you can fight fire with fire, but the evidence suggests that this isn't one of those times. Under current conditions, the increased availability and decreased price of natural gas are likely to lead to an increase in US greenhouse gas emissions. Preliminary data from 2013 suggest that that is already occurring. And global emissions are, of course, continuing to increase as well.
Insanity is sometimes defined as doing the same thing but expecting a different result. Psychologists define perseveration as repetitive behavior that interferes with learning. Whatever we call it, that seems to be what is happening. And whatever it is, it doesn't make sense. Natural gas is not the bridge to clean energy; it's the road to more climate change.
Naomi Oreskes is professor of the history of science and affiliated professor of earth and planetary sciences at Harvard University, and co-author, with Erik Conway, of Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming. She is also a co-author of Environmental Impacts of Shale Gas Extraction published by the Council of Canadian Academies in 2014. Her new book with Erik Conway is The Collapse of Western Civilization: A View from the Future (Columbia University Press, 2014). To stay on top of important articles like these, sign up to receive the latest updates from TomDispatch.com here.