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Natural gas is a bridge to nowhere

Photo by Walter DisneyPhoto by Walter DisneyA new journal article finds that methane leakage greatly undercuts or eliminates entirely the climate benefit of a switch to natural gas. The authors of “Greater Focus Needed on Methane Leakage from Natural Gas Infrastructure“ conclude that “it appears that current leakage rates are higher than previously thought” and “Reductions in CH4 Leakage Are Needed to Maximize the Climate Benefits of Natural Gas.”

Natural gas is mostly methane – a very potent greenhouse gas, though with a much shorter lifetime in the atmosphere than CO2, which is emitted by burning fossil fuels like natural gas. Recent studies suggest a very high global warming potential (GWP) for CH4 vs CO2, particularly over a 20-year time frame.

The new Proceedings of the National Academy of Sciences study introduces the idea of “technology warming potentials” (TWPs) to reveal “reveal time-dependent tradeoffs inherent in a choice between alternative technologies.” In this new approach the potent warming effect of methane emissions undercuts the value of fuel switching in the next few decades, exactly the timeframe we need to reverse the warming trend if we are to have any chance at triggering amplifying feedbacks and preventing multiple catastrophes.

For instance, the new study finds that a big switch from coal to gas would only reduce TWP by about 25% over the first three decades — far different than the typical statement that you get a 50% drop in CO2 emissions from the switch.

Note that the conclusion above is based on “EPA’s latest estimate of the amount of CH4 released because of leaks and venting in the natural gas network between production wells and the local distribution network” of 2.4%.

Many experts believe the leakage rate is higher than 2.4%, particularly for the fastest growing new source of gas — hydraulic fracturing. Also, recent air sampling by NOAA over Colorado found 4% methane leakage, more than double industry claims. The study notes:

We emphasize that our calculations assume an average leakage rate for the entire U.S. natural gas supply (as well for coal mining). Much work needs to be done to determine actual emis- sions with certainty and to accurately characterize the site-to-site variability in emissions. However, given limited current evidence, it is likely that leakage at individual natural gas well sites is high enough, when combined with leakage from downstream operations, to make the total leakage exceed the 3.2% threshold beyond which gas becomes worse for the climate than coal for at least some period of time.

In short until we have far more actual data showing low leakage rates — or regulations to ensure low leakage rates — it is hard to claim that switching from coal to gas plants has a substantial warming benefit in the near-term (that is especially true for reasons I’ll touch on below). It’s even harder to claim that simply shoving massive amounts of natural gas into the energy supply system is a good idea at all, given that some of it would inevitably replace new renewables — and if even a small fraction of new gas plants replace renewables, that eliminates any warming benefit that switching from coal to gas might have.

I had previously argued that you need a rising carbon price to ensure that any new natural gas plants replace coal and not renewables (see here). Indeed, I first made that argument three years ago — see “Why unconventional natural gas makes the 2020 Waxman-Markey target so damn easy and cheap to meet.”

But now it’s increasingly clear that a carbon price alone doesn’t address the full problem. You are going to need enforceable national standards to bring the leakage rate way down. Such standards could in fact be a very quick way to reduce the rate of global warming.

Indeed, the other shocker in this study is how bad natural gas vehicles (NGVs) are for the climate. In particular, many are trying to pass legislation for switching heavy duty diesel vehicles to natural gas. The study concludes that such a switch sharply increases Technology Warming Potential for many decades, and no one alive today would ever see a climate benefit from that switch.

This new research, coauthored by two EDF scientists as well as other leading scientists, appears to have led EDF to strongly oppose NGVs. As the National Journal reported last month:

“The president has proposed we switch trucks to natural gas, and I’m here to tell you today that every truck we switch to natural gas damages the atmosphere,” Fred Krupp, president of the Environmental Defense Fund, said at the IHS Cambridge Energy Research Associates annual conference here. Krupp said the little data available about how much methane — a greenhouse gas 20 times more potent than carbon dioxide — escapes during the production of shale natural gas compels him to refuse to support a shift toward more natural-gas vehicles.

We’re against what the president called for in the State of the Union until they [the natural-gas industry] can demonstrate they can get the leak rate down below 1 percent,” Krupp added. The Environmental Defense Fund’s opposition to the proposal is notable; it is one of the only environmental groups willing to work with industry on the concerns surrounding shale natural gas, which has been discovered in vast amounts all over the country in the past few years.

The problem for NGVs, as study coauthor and EDF chief scientist Steven Hamburg explained to me, is that the extra steps involved in using natural gas as a transport fuel — including fueling and onboard storage, increases the system leakage rate significantly. And these leaks are probably much harder to address. So the possibility that, say, the entire leakage rate for the heavy-duty vehicle infrastructure, from fracking to fueling, could ever be brought down to below 1% is pretty darn small.


The concept of natural gas as a “bridge fuel” was pushed by the American Gas Association as far back as 1981. It’s the longest bridge in history! Heck, the Golden Gate Bridge only took 4 years to build!

But the window where gas can be a major bridge fuel to a world with a livable climate appears to be almost completely closed, now. Had we acted back in the 1980s or even 1990s as climate scientists and world leaders had been urging, then, yes, an expansion of gas use might have made sense.

The fact that natural gas is now a bridge fuel to nowhere was first shown by the International Energy Agency in its big June report on gas — see IEA’s “Golden Age of Gas Scenario” Leads to More Than 6°F Warming and Out-of-Control Climate Change. The IEA’s well-named GAG scenario assumes that not only does oil production peak in 2020 — but so does coal!

Remember, warming beyond 6°F (3.5°C) is “incompatible with organized global community, is likely to be beyond ‘adaptation’, is devastating to the majority of ecosystems & has a high probability of not being stable (i.e. 4°C [7F] would be an interim temperature on the way to a much higher equilibrium level),” according to Professor Kevin Anderson, director of the Tyndall Centre for Climate Change in Britain (see here). We would be self-destructively irrational to risk even 5°F warming.

If your goal is a livable climate, we need to transition off of all fossil fuels ASAP.

September saw the publication of a remarkable study by Tom Wigley of the National Center for Atmospheric Research (NCAR), which concluded:

In summary, our results show that the substitution of gas for coal as an energy source results in increased rather than decreased global warming for many decades.

What NCAR’s new study added was more detailed modeling of all contributors to climate change from fossil fuel combustion — positive and negative. Reducing coal use reduces sulfate aerosols that have a short-term cooling effect.

The new study does not consider the potential drop in sulfate aerosols from switching off coal. It discusses Wigley’s work and argues that he overestimated the impact. But it seems likely that a significant impact remains and further undercuts the benefit of a major switch from coal to gas.

Analyzing the switch from coal to gas is certainly complicated. I’ve discussed it at length with coauthor Steven Hamburg. And I’ve run this new study by climatologist Ken Caldeira, who stands by his approach that finds basically no benefit in the switch whatsoever — see You Can’t Slow Projected Warming With Gas, You Need ‘Rapid and Massive Deployment’ of Zero-Carbon Power. Caldeira certainly supports efforts to reduce methane leakage, but as he has said before, “Natural Gas Is ‘A Bridge To A World With High CO2 Levels’.” I cannot do justice to his comments on this study by excerpting them, so I’ll post them in full tomorrow.

Doing in situ studies of actual methane leakage under different conditions is valuable. It’s great that groups like EDF are working with industry to get a better grip on this.

Cutting methane leakage sharply makes a lot of sense, but, realistically, it is all but certain to require federal standards that the industry will oppose. And who precisely is going to achieve such standards globally as the technology for fracking is exported around the world?

Building lots of new gas plants simply doesn’t make much sense since we need to sharply reduce greenhouse gas emissions and the rate of growth of warming in the next few decades if we’re to have any chance to avoid catastrophic global warming. We only want an outcome, which doesn’t exist yet, where natural gas only replaces coal. We don’t want new gas plants to displace new renewables, like solar and wind — since that would negate what little benefit switching from coal to gas might bring. That requires a carbon price.

So the only scenario I can see in which more gas makes sense is the one I laid out 3 years ago. We have a rising price for carbon. We have a short-term transition — lasting to about 2020 — to fill the existing underutilized gas-fired capacity and replace coal cheaply.

In this scenario, very few new natural gas plants are built. And, of course, during this time we still push hard on efficiency and all forms of renewables to keep bringing them rapidly down the cost curve. Post-2020 it needs to be pretty much all carbon-free power.

What this new study adds is that even this approach doesn’t make much sense without an additional effort to cut methane leaks sharply.

BOTTOM LINE: If you want to have a serious chance at averting catastrophic global warming, then we need to start phasing out all fossil fuels as soon as possible. Natural gas isn’t a true bridge fuel from a climate perspective. Carbon-free power is the bridge fuel until we can figure out how to go carbon negative on a large scale by the end of the century.

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