Could A Rapid Move Away From Coal Speed Up Climate Change?

A significant amount of the reduction in coal burning in such countries as the United States and United Kingdom has been achieved through the replacement of coal with natural gas. The resulting reductions in carbon dioxide emissions have been hailed as a success in the efforts to keep within the 20C global temperature limit.

There are a number of problems with such celebrations

  • Natural Gas predominantly consists of methane, which is an extremely potent greenhouse gas. It has been calculated that if only 3% of the methane escapes between the well site and final consumption the reduction in CO2 emissions with respect to coal is negated. Many studies show much higher than a 3% rate of such fugitive emissions.
  • Coal combustion emits sulphur dioxide particles that produce a global dimming effect, offsetting some of the warming from the CO2. As these particles only stay in the atmosphere for a short time, their levels fall rapidly with a reduction in coal burning.

In the past few years, the radiative forcing effect of methane has been revised upwards. On a 100-year basis: from 21 times that of CO2 to 34 times[1] and recently possibly higher. Over a 20-year basis: from 56 to 86 to 105 times that of CO2 and also possibly higher[2].

Atmospheric concentrations of methane have been rising rather than falling as assumed by the above numbers; i.e. decaying methane (methane stays in the atmosphere for only about 12 years) has been more than replaced by new emissions. Given this, it could be argued that an instantaneous radiative forcing number, that may be even higher still, is the most appropriate. I have not been able to find a source for what that number would be.

With respect to the 20C target, which could be broken within two decades, the available 20-year global warming potential number is more meaningful. When taking this into account, together with the reductions in SO2 aerosols, the amount of fugitive methane emissions to make natural gas worse than coal will be much less than 3%.

Any move from coal to natural gas will exacerbate global warming. Any move to reduce SO2 emissions through such things as SO2-scrubbers on coal plants, more use of low sulphur coal, and low sulphur ship bunker fuel will also exacerbate global warming. Even a move from coal to renewables will exacerbate warming in the short-term as the level of atmospheric SO2 aerosols is reduced.

Given how close we are to a level of warming that will produce dangerous, or even catastrophic climate change, any short term exacerbation may be extremely counter-productive for the survival of complex human civilization. If we significantly reduce coal usage, we may need to replace the SO2 aerosols to keep the climate within a safe space.

References

[1] Joe Romm (2015), How The EPA And New York Times Are Getting Methane All Wrong, Think Progress. Accessible at https://thinkprogress.org/how-the-epa-and-new-york-times-are-getting-methane-all-wrong-eba3397ce9e5/

[2] M. Etminan et. al. (2017), Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing, Geophysical Research Letters. Accessible at http://onlinelibrary.wiley.com/store/10.1002/2016GL071930/asset/grl55302.pdf?v=1&t=j6v3qwcd&s=b2e5f3a17d9581165ba22d6b723ba5b4e904d573

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3 Responses to Could A Rapid Move Away From Coal Speed Up Climate Change?

  1. Robert,

    Excellent article.

    Methane as usable, even as a bridge fuel is still prominently mentioned in the US. This is part of the Hydra-Headed Meta-Delusion under which our culture is operating.

    Wonderful that you are still trying to inform and have not drifted into total despair.

    Thank you,

    Michael

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  2. Joe says:

    I'm very surprised at the argument here. Short term dimming has always been a side effect of coal burning, but most of the danger to our climate comes from higher equilibrium temperatures after an increase in CO2. The sharp jump in temperature due to a clearer atmosphere (about 0.5 C) was always going to come sometime, sooner if we stop using coal sooner and later if we stop using coal later. That jump is already baked in.

    Are you suggesting that we should keep burning coal to avoid clear skies and somehow reduce other fossil fuels, especially gas, very rapidly to to make up for the CO2 from coal? That coal should be the last fossil fuel to be abandoned, despite its carbon content? You suggest that we can produce substitute aerosols as part of a climate engineering scheme and we should keep burning coal until that technology is in place. What such scheme is nearly ready to go?

    I just find it hard to justify weighing the short term benefit of coal aerosols over the long term damage of the extra CO2 from coal, especially since it is very unlikely that we can ever replace the function of those aerosols by other means. I also think you are overly concerned with the short term effects of methane. Atmospheric methane concentrations have gone up 0.15 ppm over the last 30 years. Even at 80 times CO2 warming potential, that is equal to an increase of 12 ppm CO2. During the same 30 years CO2 has gone up about 60 ppm, five times as much. About 10 percent of human methane emissions comes from coal mining, so coal has its own methane problem too.

    We should be thinking of the next few centuries, not the next few decades. All sources of CO2 should go to zero ASAP (including methane), especially since no one really knows when natural positive feedbacks might take over.

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    • rboyd says:

      Taking into account the fugitive methane and SO2, fracked natural gas has a higher warming than coal over 100 years (and even greater over 20 years). So replacing coal with fracked gas does nothing for climate change, and actually increases the level of warming (even using the GWP100 for methane).

      As you say, the focus should be on replacing fossil fuels not replacing one with the other. I am concerned that we have a number of factors driving a near-term acceleration in climate change which we do not need to add to given how close we are to possible feedbacks.

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