Over-heaters Anonymous:the Methane Diet

by Stephen Shafer on June 24, 2019

                        flooded streets                    

                                                                                      Why We Must Control  Methane Emissions Now!

Note:  title of this post has been changed to that right above,  because the original title was a weak pun about a serious topic.  I have not changed the permalink,, since that is in  circulation already.  http://www.anchorageromneys.com/2019/06/over-heaters-a…e-methane-diet

Summary:  This picture-essay   explains  why methane  must be considered very differently from  carbon dioxide as a “greenhouse gas” that powers “global warming.”     It  opens with a brief explanation of global warming, then compares how methane and carbon dioxide differently affect  the capacity  of the atmosphere to trap heat over time.  Humanity has a chance to modify over the next ten years  how methane will influence  near-future global  warming.  To change it for the better is possible.   We don’t have that potential with carbon dioxide.  Therefore, we must act on methane immediately.    The best place to start  is by ending the growth of the natural gas supply system in the United States. 

            A windows-up car in winter sun is warm inside.  The sunlight  that went  through the glass has been  repacked  inside to  another form of  energy (infra-red) that can’t get out  through glass as readily  as  the light came in; so, some   stays a while, warming the  inside.   Greenhouses work  this way,  too,  trapping heat. 

            Earth’s  atmosphere acts like  glass  because “greenhouse gases”  in it let through solar energy but  restrict the return to space of  infra-red, heating  the atmosphere.    For thousands of years the atmosphere acted   like a well-run greenhouse, with carbon dioxide ( the main greenhouse gas)  recycled  to earth so it did not build up in the atmosphere.  In the 1800s,  mounting  releases  of greenhouse gases   (mostly carbon dioxide from burning fossil fuels for heat and power)  overloaded the atmosphere’s pre-industrial ability to handle them.   Each year, less incoming energy escaped back into space.  This trend has sped up greatly in the last fifty years.  The needed,   beneficial “greenhouse effect”  that fostered  plant and animal life is  out of control.  This raises the  average  temperature at Earth’s surface.  It   causes “climate change”  featuring  rising sea levels,  warmer and acidifying oceans, deadly heat waves, droughts , mass extinctions, melting glaciers,    record-breaking rains and floods.

            Carbon dioxide from burning coal, oil and natural gas accounts for more than half  of  the  heat now stuck  in the atmosphere.  Any carbon dioxide  beyond what  can be recycled to earth via photosynthesis in plants  or (with ill effects) dissolved  in oceans builds up  in the atmosphere, where it  will last  for  centuries.  Another greenhouse gas, methane,  is scarcer but so much  stronger  per molecule at stopping  outward-bound energy that methane causes almost  a third as much heat-trapping as carbon dioxide.     Methane is short-lived.  It survives  in the atmosphere only about ten years before it’s  broken up   by “scrubber” chemicals.  This gives  humans potential to get  more control on   global over-heating  than we now have,  if and only if we take steps that are big but not impossible.. 

            How methane and carbon dioxide differ as atmospheric heat-trappers is  shown in a series of  eight pictures below.  The first four  represent the atmospheric warming effect of  just methane alone; the next four,  the atmospheric warming effect of  just carbon dioxide alone.  In real life the two gases are combined  in the atmosphere, with their combined warming effect being that of carbon dioxide PLUS that of methane.

            The atmospheric warming effect of  methane alone  in 2019  is represented in figure 1 by two  blankets on the doll. Imagine she’s a real person who’s comfortable under two. 

 two blankets

Fig. 1  Warming effect of methane in 2019.  Two blankets

          If global methane emissions stayed the same per year for the next ten years,   each unit entering  the atmosphere after 2029  would replace one that had been scrubbed out.  This would sustain global heating by methane  at  2019  levels but not make it worse.  The 2029 situation is represented in figure 2 .   The doll still has two blankets.

 

two blankets Fig 2. Warming effect of methane in 2029 if  amount emitted each year since 2019 has not changed

        If  global methane emissions began to go down year by year, there would be cooling in 2029,   because not all the  heat-trapping methane molecules that had been scrubbed out would be replaced by new ones.  The doll in figure 3 is “sleeping cooler”   with now only one  blanket, not  two.

 one blanket

 Fig. 3.  Warming effect of methane 2029 after 10 yrs of emissions going down every year ,  not to zero

            On the other hand –worst case – if methane emissions keep rising worldwide,  methane  will add  to global over-heating at an extreme rate.  You can imagine that  the  doll in Figure 4 below will be very hot  under four blankets.

 4 blankets

 Figure 4 .  Warming effect of  methane in 2029 after ten years of rising emissions.

            Someone  might say “Duh, obviously when emissions are going up the  heating effect is stronger, like more blankets.  Everybody knows that.”  OK,  but what  everybody does  not  know is that  the heat content of the atmosphere will respond quickly to changes in how fast  methane is entering  it,   because methane is short-lived.   It doesn’t work that way with  long-lived carbon dioxide.   The response is delayed, blunted.  With  either  gas, emissions going up year after year  will increase atmospheric heat content (add blankets) and raise the doll’s temperature.  BUT, carbon dioxide’s contribution to  atmospheric heat content,  unlike methane’s, will keep rising for decades  even if emissions are flat, even if they  are falling. 

            Figure 5 represents the warming effect of carbon dioxide in 2019: six blankets

 6 blankets

  Figure 5.  Warming effect of carbon dioxide alone  in 2019 represented by 6 blankets

 

         Figure 6 shows the situation in 2029 assuming that carbon dioxide emissions have been exactly the same amount per year since 2019.  Eight blankets, not six. All the heat-trapping gas emitted in those ten years has been added to what was already there in 2019.

8 blankets

  Fig, 6  Warming effect of carbon dioxide alone in  2029 if emissions each year   are unchanged: 8 blankets

           

            If carbon dioxide emissions got to be  less each year than the year before, the situation in 2029 would look like figure 7.   There are seven  blankets, not six  and not eight.  The total added in ten years is less than what it would have been if the amount each year had stayed the same, but it’s still a big extra load.

 seven blankets

   Figure 7. Warming effect of carbon dioxide in 2029 after 10 years of falling emissions

            If  each year’s emissions of carbon dioxide were higher than those the year before,  the scene in 2029 would be like Figure 8, with nine blankets piled on,

 9 blankets

   Fig. 8  Warming effect of carbon dioxide in 2029 after 10 years of rising emissions: 9 blankets

            The table below  summarizes the eight pictures by counting the number of blankets in each situation. For example, two blankets for methane in 2019 (Figure 1) and seven for carbon dioxide in 2029 after ten years of declining emissions.(Figure 7).    The take-home message is that the future heat trapped (number of blankets) due to carbon dioxide will always be higher than that of today for many decades to come,  no matter whether the amounts released per year stay the same, go up or go down.  Methane is different.  Future heat-trapping  due to methane will not necessarily be higher; it could be the same or even lower if humankind takes ambitious steps. 

 

Methane

Fig no.

Carbon dioxide

Fig no.

2019 “baseline”

2

1

6

5

 2029 emissions same each year

2

2

8

6

2029 emissions falling each year

1

3

7

7

2029 emissions rising each year

4

4

9

8

 

            To put things another way,  humanity can apply the brakes to methane’s role in adding heat to  the atmosphere.  There are no brakes on carbon dioxide that will work anywhere near as soon.

            Even cutting   global methane emissions to zero  (impossible, since  almost half are  from sources outside human influence like wetlands and  lakes) would not halt  the runaway  greenhouse effect we see now.  To turn the corner on over-heating, carbon dioxide emissions must end and  much of  it  now in the atmosphere  must  be moved into soil for good.  The point about methane, however, is that  letting  its yearly emissions grow will add hugely  to global over-heating .  but  holding them steady will not.   Cutting them year after year will actually remove heat. 

            To be clear: neither holding total methane emissions steady over the next few years  nor sharply reducing them will necessarily keep the average temperature on the globe’s surface from hitting  dangerous new heights towards  which it is headed.  The other side of that statement is that letting methane emissions continue to go up in the near future guarantees that the danger point will be reached, and sooner.

            How to get yearly methane emissions down ?  The major sources under human influence are, in order of amount : fossil fuel extraction and distribution; livestock  that release methane in digestion; paddy rice cultivation,  landfills and waste handling; biomass burning.

 pie Howarth jpg

  Figure 9. Global human-influenced methane emissions in million tonnes/yr, by source.  Data:  Howarth, 2019

            The major  source – fossil fuels — is also the only one that on good evidence is getting bigger each year.  This is due  largely  to  leakage of methane from the natural gas withdrawal   and distribution system (natural gas is mostly methane) .   In the USA, natural gas withdrawal rose by 69% between 2006 and 2018, spurred by “fracking.”  The more natural gas is pumped from the earth,  the  more methane leaks   into the atmosphere.  A quick end to  growth  of the natural gas industry  in the  USA could put the world on course to steadily  flat or falling methane emissions, not adding further  to atmospheric heat , maybe even lessening it over time .  Continued expansion of  leaky natural gas systems, in terrible contrast, would cause yet more  heat to be trapped our atmosphere,  already too warm.

            A “quick end” to growth does not mean that everyone who now uses natural gas will have it turned off.   It  does  mean that no new projects to withdraw and use it can be tolerated if we want a decent  chance for a livable world for our children and grandchildren.  In short,

  • No new gas wells, fracked or conventional
  • No new gas pipelines, long or short
  • No new gas-fired power plants
  • No new gas storage facilities
  • No new buildings hooked up to natural gas
  • No exports of liquefied natural gas for  fuel or plastics
  • Start closing  “fracked”  wells
  • Carbon fee (and dividend)  on natural gas (with agricultural exemption)
  • Top priority for renewable energy sources like wind and solar
  • No federal subsidies for natural gas systems

            That’s a tall order, but to get from current rate of growth/yr  in methane emissions to no growth could almost be done by rolling  US natural gas withdrawals back  to where they were around 2006 and  making sure that methane from livestock holds steady. 

 

Further reading

http://www.eeb.cornell.edu/howarth/documents/Howarth_methane-Biogeo-lecture_2019-0301.pdf

https://foodsource.org.uk/building-blocks/agricultural-methane-and-its-role-greenhouse-gas

Stephen Q. Shafer MD MA MPH  Saugerties NY 12477   sqs1@columbia.edu

 Any errors of fact or interpretation are entirely mine as an individual. as are all opinions expressed.  Permission is hereby given to copy or circulate  the above piece in whole or part as long as the permalink is cited.

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