If you haven’t seen them already, you may want to read this post about GWP and this post about GWP* first.
So should we abandon GWP for methane emissions and begin using GWP* instead? That’s what many advocates for beef, dairy, and sheep have been arguing. It’s even found support within some national governments—countries where sheep and cattle are an important part of the economy.
The thing is, switching to GWP* would be a major giveaway to any industry that generates ongoing methane emissions.
Take a look at the visualizer here. Set it to:
- MtCH₄ emissions at start: 1.0
- MtCH₄ emissions at start: 1.0
- Years: 30
The visualizer assumes that the emissions have been ongoing at the “emissions at start” level for a couple of decades prior to year 0—enough time for the CH₄ levels in the atmosphere to have stabilized. And that means that if an operation keeps its CH₄ emissions at the same level into the foreseeable future, it won’t cause the CH₄ concentration in the atmosphere to go up.
Now recall that GWP*-proponents do acknowledge that there are some long-term effects of methane even after it has been removed from the atmosphere. The equation takes account for this phenomenon. Still, it is much smaller than it would be using the conventional GWP definition.
As Professor Frank Mitloehner, a GWP* champion from UC Davis put it, “A constant livestock herd produces a constant amount of methane, but almost an equal amount of methane that’s produced by a constant herd is also naturally destroyed and that means when you have a slight reduction of methane per year and that reduction is 0.3% … then you are not causing additional
warming.’’
But what does that phrase “not causing additional warming” really mean? Let’s think of it another way. Suppose that, once every year, a burglar stole $10,000 from the homes in his neighborhood, and had been doing so for decades. Finally he gets caught. And when he is brought in front of the judge, he argues that he should be let go because even though he just stole $10,000, his action had not increased the overall burglary rate in the city?
Or what if this burglar were to take it to the next level. Suppose that he only stole $5,000 for a few years. Should he then go to the mayor and ask for a reward because he had actually reduced the city’s burglary rate? Sounds crazy, but that is exactly what GWP* would allow. Go to the visualizer and set it to:
- MtCH₄ emissions at start: 1.0
- MtCH₄ emissions at start: 0.5
- Years: 30
See how the blue line in the second graph actually dips into negative territory? If a dairy farm were to cut the size of its herd in half it could claim not just that it had reduced its emissions. It could claim to actually be generating negative emissions, as though it were sucking CH₄ out of the atmosphere.
For a much more detailed look at these issues, take a look at the report Seeing Stars: The New Metric That Could Allow The Meat And Dairy Industry To Avoid Climate Action by the Changing Markets Foundation. On p. 22 they even provide some actual emissions numbers for the meat company Tyson Foods and the dairy company Fonterra, showing how they would benefit from the use of GWP*.
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