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First the link to this week's complete list as HTML and as PDF.
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I’m not sure what Gibson et al. study Nigra believes to have read. Yes, the number 20 % does crop up in one of the diagrams without any pertinent data been shown or given and without the derivation explained. The average blood lead load from private wells is 17.5 µg/l versus 15.9 µg/l from the public water supply. This difference of 10.0 % is one of the smallest among all the possible influences considered. As nearly all the confounders point in the same direction, adjusting for them can only lower not raise that raw base value.
Apart from that these tiny differences, all below the 20 µg/l mark, are meaningless anyway. What matters are critical values above 50 or 90 µg/l. These too occur but no data for them are given at all, much less presented in a diagram. If Gibson et al. have shown anything, it is that lead can be a problem but water source is an irrelevant parameter for trying to cure it.
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Malhotra et al.'s experimental results look sound. What is a bit puzzling is their conclusion (absent from their headline, seemingly added to the abstract as an afterthought, but prominently stated in reviews and summaries). It is unclear how more plant growth, more biomass generation and more carbon dioxide uptake translate into less carbon storage. The only hint they give for this assumed connection is a bit of hand waving in their penultimate paragraph. I'm no biologist, perhaps I'm missing the obvious here, but I don't see this claim substantiated.
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Models are not data. Treating model results as data leads to false conclusions. I have stated this simple fact many times and Smith et al. and Voosen provide another example for it being true.
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