A BRIDGE FUEL TO NOWHERE
A stunning new study by the National Center for Atmospheric Research (NCAR) concludes:
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….
Coal, natural gas, and climate: Shifting from coal to natural gas would have limited impacts on climate, new research indicates. If methane leaks from natural gas operations could be kept to 2.5% or less, the increase in global temperatures would be reduced by about 0.1 degree Celsius by 2100. Note this is a figure of temperature change relative to baseline warming of roughly 3°C (5.4°F) in 2100. Click to Enlarge.
The fact that natural gas is 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. That study — which had both coal and oil consumption peaking in 2020 — made abundantly clear that if we want to avoid catastrophic warming, we need to start getting off of all fossil fuels.
But what NCAR’s new study adds is more detailed modeling of all contributors to climate change from fossil fuel combustion — positive and negative. The study is here [they just eliminated the subscription requirement], the news release is here. It’s by senior research associate Tom Wigley, one of the country’s leading experts on climate modeling.
“Relying more on natural gas would reduce emissions of carbon dioxide, but it would do little to help solve the climate problem,” says Wigley, who is also an adjunct professor at the University of Adelaide in Australia. “It would be many decades before it would slow down global warming at all, and even then it would just be making a difference around the edges.”
Wigley’s analysis is the first to include all of the relevant climate factors:
We consider a scenario where a fraction of coal usage is replaced by natural gas (i.e., methane, CH4) over a given time period, and where a percentage of the gas production is assumed to leak into the atmosphere. The additional CH4 from leakage adds to the radiative forcing of the climate system, offsetting the reduction in CO2 forcing that accompanies the transition from coal to gas. We also consider the effects of methane leakage from coal mining; changes in radiative forcing due to changes in the emissions of sulfur dioxide and carbonaceous aerosols; and differences in the efficiency of electricity production between coal- and gas-fired power generation. On balance, these factors more than offset the reduction in warming due to reduced CO2 emissions.
In the main scenario in the paper, natural gas use soars and coal use drops from 2010 to 2050 before rising again slowly. In the “Supplementary Material,” Wigley runs a sensitivity analysis where natural gas actually replaces coal entirely by 2050. The results are virtually identical — there’s extra warming through 2050 and by 2100 the total reduction in warming is slightly under 0.1°C.
Wigley’s warming in 2100 is “only” 3°C (though it just keeps warming and hits 4°C a few decades later). Other models show 2100 warming closer to 4°C or 5°C (see M.I.T. doubles its 2095 warming projection to 10°F — with 866 ppm and Arctic warming of 20°F). Either way, the switch to gas accomplishes little or nothing.
A key finding of the NCAR study is:
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. This is in accord with Hayhoe et al. (2002) and with the less well established claims of Howarth et al. (2011) who base their analysis on Global Warming Potentials rather than direct modeling of the climate….
The most important result, however, in accord with the above authors, is that, unless leakage rates for new methane can be kept below 2%, substituting gas for coal is not an effective means for reducing the magnitude of future climate change.
What is the leakage rate for methane? Well, as I’ve written, we don’t know exactly because the gas companies won’t release all of their data. We do know that total life-cycle leakage and fugitive emissions from extraction, production, transport, and consumption is higher for shale gas than conventional gas.
The controversial — but peer-reviewed — paper by Cornell’s Robert Howarth, which I wrote about here, seeks to quantify the impact of the leakage from the best available data. It concluded:
Natural gas is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life-time of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured — as methane escapes from flow-back return fluids — and during drill out following the fracturing. Methane is a powerful greenhouse gas, with a global warming potential that is far greater than that of carbon dioxide, particularly over the time horizon of the first few decades following emission.
I wrote about the “response” by the National Energy Technology Laboratory, the DOE’s premier fossil fuel lab, here. NETL throws dozens of numbers at the reader — and averages in shale gas with conventional gas — to obfuscate the issue. But even NETL concedes that fugitive emissions comprise 1.7% of all natural gas extracted — and point source losses (vented or flared) comprised 2.4% of gas extracted. Shale gas, in their analysis, appears to have 30% higher global warming potential for extraction and delivery, so clearly total losses are higher — much higher than 2%.
I would note that legitimate claims are being made now that the lifetimes of many new shale gas wells have been overstated considerably — see “Analysis: U.S. Shale Gas Industry Reserves Are Over Stated at Least 100 Percent.” If so, this would again suggest that total life-cycle emissions relative to total production may be higher than people have suspected for unconventional gas.
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.
Can’t argue with that.
Reid Detchon, executive director of the Energy Future Coalition is quoted saying:
Certainly the carbon benefit was a major consideration in wanting to consider a switch from coal to gas. The Wigley analysis makes it clear that simply switching from coal to gas is not going to get the job done.”
Detchon calls for developing carbon capture mechanisms for natural gas, which should be a priority for the industry, but don’t hold your breath.
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.
Since this is an NCAR study, let me end by pointing out that last year NCAR published a complete literature review of “Drought under global warming” (see here). That study makes clear that Dust-Bowlification may be the impact of human-caused climate change that hits the most people by mid-century, as the figure below suggests (click to enlarge, “a reading of -4 or below is considered extreme drought”):
The PDSI [Palmer Drought Severity Index] in the Great Plains during the Dust Bowl apparently spiked very briefly to -6, but otherwise rarely exceeded -3 for the decade (see here).
The large-scale pattern shown in Figure 11 [of which the figure above is part] appears to be a robust response to increased GHGs. This is very alarming because if the drying is anything resembling Figure 11, a very large population will be severely affected in the coming decades over the whole United States, southern Europe, Southeast Asia, Brazil, Chile, Australia, and most of Africa.
The National Center for Atmospheric Research notes “By the end of the century, many populated areas, including parts of the United States, could face readings in the range of -8 to -10, and much of the Mediterranean could fall to -15 to -20. Such readings would be almost unprecedented.”
Texas is currently at a PDSI of -7.75, close to its record of -7.8 in September 1956 — see Hell and High Water Stoke Texas Blaze: “No One on the Face of This Earth has Ever Fought Fires in These Extreme Conditions”
For the record, the NCAR study merely models the IPCC’s “moderate” A1B scenario — atmospheric concentrations of CO2 around 520 ppm in 2050 and 700 in 2100, which looks close to what Wigley modeled. If this is the Golden Age of Gas, then it must be describing the color of the dust.