Daniel Lemire's blog

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Science and Technology links (October 20th, 2018)

6 thoughts on “Science and Technology links (October 20th, 2018)”

  1. Thomas Friedel says:

    There was a recent story about a study that suggested that eating meat has a very big impact. So it very much contradicts the study you posted. I wonder which one I should trust more.

    1. Is there really a contradiction?

      That is, does the research you link to says that stopping the use of animals in US farming would reduce greenhouse gas emissions by a lot more than 2% in that country?

  2. Thomas Friedel says:

    “For the United States, where per capita meat consumption is three times the global average, dietary change has the potential for a far greater effect on food’s different emissions, reducing them by 61-73%. See supplementary text for diet compositions and sensitivity analyses and fig. S14 for alternative scenarios. ” [2]

    In the study by White & Hall they mention “decreased agricultural US GHGs (28%)”. So if this is wrong and it’s actually 61-73%, it would mean the total US GHGs would be reduced by 5.5-6.6 percentage units instead of 2.6.

    1. it would mean the total US GHGs would be reduced by 5.5-6.6 percentage units instead of 2.6.

      Ok. So stopping the use of animals in farming for the US would, one conjectures, reduce greenhouse gas emissions by about 6 percent.

      What are the emissions due to agriculture as a whole? Maybe the EPA is a trusted source on this?

      In 2008, emission sources accounted for in the Agriculture chapter were responsible for 6.1 percent of total U.S. greenhouse gas emissions. Source: https://www.epa.gov/sites/production/files/2015-12/documents/us-ghg-inventory-2010_executivesummary.pdf

      Right. So agriculture as whole is responsible for 6.1 percent of all US greenhouse gas emissions.

      So, no, I don’t think it is credible that we could see a drop of 5.5 to 6.6 as you suggest. That’s if you stop all agriculture, entirely.

      You have to watch the math also, because if, say, animals are responsible for, say 3.5% of greenhouse gas in the US, if you stopped it, it would not lead to a 3.5% reduction. Because, obviously, if you stop eating meat, you are going to eat more of something else. I think that the 2.6% is quite credible. You can argue on details… maybe it is 2.8% or 2.5%… But it is not 6%, 10% or 30%…

  3. Thomas Friedel says:

    From the White & Hall Paper:
    “Assuming agricultural emissions account for 9% of total US emissions (47), and assuming that emission estimates here are representative of national emissions, eliminating animal agriculture would decrease total US emissions by an estimated 2.6 percentage units.”
    They also use the EPA as a source for that number. In a more recent report (yours used a number for 2008) you find 8.6% for CO2. I guess other greenhouse gases have been reduced since 2008?

    So yes it can be reduced by about 6% if we assume 9% for total agriculture emissions.
    This argument, that you would eat something else instead is correct and has been carefully considered in the study by Poore. If you look at the supplementary materials you will find a table where they looked at different diet scenarios.
    I wonder what the upper and lower bounds for those estimates actually look like. There’s a lot of assumptions stacked on assumptions, numbers from different sources combined etc. And different people get wildly different results.

    Now should we be concerned about 6%? I think so. It’s a big chunk of agriculture. Transport is also about 9% and if we could reduce that by 2/3 it would be considered a big achievement.

    1. If you believe that 70-80% or so of CO2 emissions due to agriculture are due to farm animals, then I would agree that a reduction of 6% of the total CO2 emissions could be in the realm of possibilities… but that’s an extraordinary claim.

      But let us suppose we believe this extraordinary claim.

      Note that the whole plan implies all of the US population goes vegan. Even if you believe in the 6% figure, it relies on an extraordinary social transformation the like of which we have never seen.

      As for the diet prescriptions, as explained by White and Hall, you cannot merely count proteins and calories. That’s obviously wrong. Maintaining a healthy diet made of tofu and soy milk is possible, but it is tricky, especially at the kind of scales we are talking about.

      But let us assume that the US undergoes this transformation… everyone in the US forgoes meat, milk, cheese, and fish tomorrow. We somehow manage to make it so people don’t get sick in the process. Done deal. But then, are we assuming that the money that people do not spend on meat is spent on carbon-neutral activities? This is very likely wrong.

      Transport is also about 9%

      Let us eyeball it, will we? (EPA numbers, again.)

      Transportation, electricity and industry are much bigger contributors than agriculture:

      Agriculture is closer to residential and commercial.

      I want to stress again that I think that there are good arguments for going meatless. I just don’t think that climate change passes the common sense test as a justification for becoming vegan.