We’ve written before about the developing science regarding the potential global warming benefits of a switch from coal to natural gas (see here, here and here).
And now, we have a new paper out in the journal Climate Change Letters that projects a switch to gas won’t have an appreciable impact on global warming, at least not in the next few decades.
Tom Wigley, a senior scientist at the National Center for Atmospheric Research, concluded in the paper:
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 — out to the mid 22nd century for the 10% leakage case.
In a news release, the National Center for Atmospheric Research explained:
The burning of coal releases more carbon dioxide than other fossil fuels, as well as comparatively high levels of other pollutants, including sulfur dioxide, nitrogen oxides, and particles such as ash. Since natural gas emits lower levels of these pollutants, some energy experts have proposed greater reliance on that fuel source as a way to slow down global warming and reduce the impacts of energy use on the environment.
But the effects of natural gas on climate change have been difficult to calculate. Recent studies have come to conflicting conclusions about whether a shift to natural gas would significantly slow the rate of climate change, in part because of uncertainty about the extent of methane leaks.
Wigley’s new study attempts to take a more 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.
It continues:
By running a series of computer simulations, Wigley 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 in a hypothetical scenario of zero leaks, which would result in a reduction of warming by 2100 of about 0.2-0.3 degrees F (0.1-0.2 degrees C). But in a high leakage rate scenario of 10 percent, global warming would not be reduced until 2140.
Wigley said:
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.
There’s more coverage of this study from the L.A. Times and the Boulder Daily Camera.
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I have not read the studies to which you have referred in this and earlier posts, but I wonder if these studies account for the significant efficiency advantage that combined cycle natural gas electrical generators have over coal fired generators. This efficiency advantage, of course, is difficult to factor into a study, because there is no way of knowing if US power companies will take advantage of it.
Phillip Schewe, in his book The Grid, does a very good job of summarizing this comparison. Here is a link to my discussion, including an extensive quote from the book, on the Coalition for Reliable Power site – http://forreliablepower.com/1/post/2011/09/another-way-to-look-at-efficiency.html.
Schewe points out that current coal fired power plants only operate at about 30 to 35 percent efficiency. That means up to 70 percent of the coal that is burned in these plants does not produce any electricity. Also, these plants, because they are so big and produce so much pollution, cannot be built near communities and other businesses where this surplus heat could be used.
On the other hand, combined cycle natural gas generators operate at about 55 percent efficiency. These plants can also be scaled down so that they can operate in communities where almost all of their surplus heat can be used in homes and businesses. This raises the efficiency of these plants to about 95 percent, according to Schewe.
While this level of efficiency is not common in the US, where power companies seem to want to replicate much of the coal based infrastructure with their new gas fired plants, it is now required in countries like Germany and Denmark.
I understand that much of the natural gas industry’s greenhouse gas impact comes from direct leakage of methane, which is much more damaging than carbon dioxide emissions from coal burning. On the other hand, leakage can be controlled and would dramatically tip the balance back in favor of gas. If combustion efficiencies in electrical generation are included, it would seem that gas is still the fuel of choice.
It is important to see the conclusions of these studies not as “which is better, coal or gas” but as guides that tell us what we have to do to reduce emissions. Considering that there are lots very practical options to limiting gas emissions and increasing the efficiency of power production, it still seems that gas is the more doable solution.
Bill,
The real question with the series of studies that have come out recently isn’t so much whether coal is better than gas — though I and the rest of the mainstream media have probably framed it that way, and not done a very good job in that regard.
The real question is: Should we be banking on natural gas as a “bridge” fuel from coal to renewable energy, and does doing so really help deal with climate change.
Joe Romm’s take on this latest study was:
“… if we want to avoid catastrophic warming, we need to start getting off of all fossil fuels.”
http://thinkprogress.org/romm/2011/09/09/315845/natural-gas-switching-from-coal-to-gas-increases-warming-for-decades/
Romm continues:
ClimateWire (subs. req’d) quotes Howarth, who is a professor of ecology and environmental biology, that the switch from coal to gas has been “overhyped”:
It’s time to move on truly green energy technologies — solar, wind — and to place a much greater emphasis on energy efficiency.
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 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 in the second half of the century.
Ken.
As you noted, “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.” But the “as soon as possible” is the big question here, isn’t it?
In the best of all possible worlds, we could snap our fingers and it would happen.
Most people in the gas industry do simply see gas replacing coal in the current structure of the US electrical system, and that is clearly not a solution.
The fact is that the entire system needs to be restructured from large scale centralized generation into much more local distributed generation from a wide variety of sources. Natural gas fits into a renewables oriented system because gas is the only fossil fuel that can be used intermittently between the surges of solar and wind generation.
The long term solution to intermittent wind and solar generation is grid scale storage batteries and smaller scale generation units that require smaller storage units. That is still a few decades away.
So this really boils down to what you see as the “transition” that gas represents. That transition must be away from bigness to widely distributed smaller generation units, which gas is also good at, and also away from coal to renewables. The transition must be a transition with a clear end point where gas is no longer needed. That is clearly not the kind of transition that Aubrey McClendon envisions.
It is one thing to agree with Jim Hansen on global warming, and quite another to actually designing a way for the US economy to get from here to there when there is almost no political or business will to do so.
Just saying we have to stop burning fossil fuels doesn’t make it happen. We need clear practical plans, and gas has some attributes that lend it to being part of a practical plan for change. That may not always be true in the future, but it remains an option for the time being.
Thanks, Bill. Just for the record, this is a quote from Romm, not my own writing:
“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.”
Ken.