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Bjorn Lomborg @BjornLomborg
, 24 tweets, 7 min read Read on Twitter
I’ve been criticized for cherry-picking. Really?
I show going vegetarian cuts 1-9% of emissions, use central 4.3%. Half lost in rebound, so ~2% actual reduction
My critics say 1-9% should be 1.5-9%. They cherry-pick 9%, round up to 10%, ignore rebound and claim 10%
In a new oped I show how going vegetarian won’t cut your greenhouse emissions much: not the often-promised 50% but more likely ~2%…
I use a meta-study (not cherry-picking lowest or highest number): going vegetarian most likely reduces emissions 540kgCO₂e, 4.3% of per cap industrial emissions of 12,440kgCO₂e (20-35% of *diet emissions*)…
Moreover, bc vegetarian diet cheaper, changing leaves you more money to spend on other stuff, increasing your other emissions. This is “rebound.”
One Swedish study finds this most likely to halve benefit to 2.1% rather than 4.15% (192kgCO₂e rebound)…
Now, two researchers criticize my findings as “cherry-picking” to “trivialize the impact of vegetarianism” and demonstrating that “climate defeatism is the new climate denial”…
They correctly point out that only two studies of the 7 studies in the meta-review include emissions from deforestation
They then take one of these studies to show that going vegetarian cuts 10% in personal emissions
But wait a minute:
of course, all studies should take all issues into account (they never do)
That’s why you use a meta-study (all papers leave out something, but taking them together eliminates cherry-picking)
Why do they only focus on deforestation (or more correctly so-called dLUC)? How big is it? They don’t tell you. But one of the papers they like and cite, does:
It is 52kgCO₂e or 0.42% of impact of going vegetarian…
Here is distribution from meta-study, based on table A1
Wide variation from lowest to highest estimate, which is why meta-study is needed to say something reasonably correct about impact of going vegetarian (the best estimate from meta-study is 540kgCO₂e)
My critics have chosen just the two red studies, which just happen to be two of the highest estimates with the ostensible reason that the others have left out 52kg CO₂e
Looks like cherry-picking
But how do they get 10% rather than 4.3% from the metastudy?
They disregard the lower of their two cherry-picked studies (Meier, 4.05%) and round up [!!] the highest (Hoolohan, 9.00%)
Definitely cherry-picking
But what about rebound? Going vegetarian frees up resources you then spend on other products, increasing your emissions.
This is well-described in literature, and can often lead to much lower emission reductions (or even increases) e.g.…
My critics simply ignore rebound and talk about other stuff:
1) How is it relevant Swedish paper relies on data from 2006? Ironically, both their favorite papers rely heavily on data from 2006: Hoolohan’s LCA estimates are from 2006 and 2008, Meier estimates food intake for 2006
2) Correct Swedish study not include deforestation, but irrelevant: I don’t use the study’s estimate of going vegetarian (though it falls right in the middle of meta-study’s interval at 389kgCO₂e)
I use Swedish study for rebound. Deforestation has *nothing* to do with rebound
3) They cite Swedish study’s very honest description of limitations to estimates of CO₂e reduction from going vegetarian“ (similar arguments would apply to all the studies in metastudy)
But again, this has *nothing* to do with rebound
Indeed, the Swedish study explicitly shows how *any* realistic modeling of rebound means a diminishment of the reduction from going vegetarian. My critics simply chose to ignore this
Ironically, my critics’ favorite article, Hoolohan, explicitly backs up the rebound point: Instead of the Swedish finding that going vegetarian reduces costs by 1.89%, Hoolohan finds it reduces costs by 3%, allowing for 3% other purchases
The rebound effect of 3% more spending on everything else is estimated by assuming proportional spending on all other products (Swedish article shows this is likely a slight underestimate), approximately 373kgCO₂e (=3%*12440)
So their own, favorite article indicates a *higher* rebound effect than what I show
But despite a lot of verbiage, they simply ignore the rebound effect
tl;dr: Going vegetarian cuts your greenhouse emissions ~2%
Critics cherry-pick studies and ignore economics, hence exaggerate impact of going vegetarian about 5x
Addendum: This discussion question of likely size of impact – unlikely 2.1% exactly correct answer. But based on best estimate from meta-study along with best estimate for rebound
Picking the absolutely highest number and ignoring rebound is extremely likely to be exaggerated
Publisher @ConversationUK wants to be “a place for intelligent discussion.” Surprisingly, they never approached me before distributing this questionable analysis
(OBS: it is only direct land use change (dLUC) that is left out in other papers,
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