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9May 2012

(UPDATED*) AP, lots more: Ancient global warmings had no SUVs, sure. But some episodes had burping, pooting DINOSAURS!

Y'know, don't you, that strain of climate contrarian humor that evokes SUVs so often?  Maybe some scientists or other science-interested person makes note of the greenhouse effect on Venus, or during the Eemian or during the early Earth and dim Sun days. In a blink somebody hoots, hah! Tell it to Al Gore! Did they have SUVs back then or what!? Perhaps a few of them do so while looking proudly at giant Lexus GXs or Lincoln Navigators in the drive. Such things are superb vehicles, of a type that America invented and good for us. If  you have a family and a horse trailer to haul and frequent need to get off the pavement, saddle-up. But they do look sort of stupid picking up one or two kids every day with their big motors idling in the line to get to the pick-up zone and the AC full-on or performing similar routine chores. Fact is, one doesn't see so many of the huge ones anymore. Maybe that's what the post-Cretaceous mammals asked after shaking off the comet dust. You seen any of those big things lately?

This week brought up another global warming gas news event that invites giggles, especially from headline writers. The news, in a letter that researchers in England and Scotland have in this week's Current Biology, a Cell Press publication, has a title that says it all:  Could methane produced by sauropod dinosaurs have helped drive Mesozoic climate warmth? Good question, and that doesn't even count the hadrosaurs (duck bills), ceratopsians, and a bunch of other dinos that ate plants and presumably ate and erupted swampy vapors all their live long days.  The answer to the title is yes, probably.  The authors calculated biomass from published density estimates (an astounding dozen or so long-necked monsters per square km, or around 30 per square mile) times habitat area and so on and so forth, corrected  for guesswork on how their methano-matabolisms compared to modern mammal herbivores, and bingo - about as much gas as from all the modern world's herds of livestock. Maybe more. And cows and things are presumed to drive a minor but not unimportant share of contemporary warming. It's of some interest that their letter closes with a thank you to the late Lynn Margulis "for infecting us with her microbial enthusiasm." That doesn't fit easily in news stories. But farts do.

Stories.

Perhaps I'm wrong, but no reporter appears to have had the gumption to call around and ask just what percentage of global warming today can be put on farm animals, meaning domesticated herbivore methanogenesis.  Is it five percent? What? LATE AMENDMENT: Seth B. saw this post, and answers thus:

Gavin Schmidt at NASA calculated that the  2 ppm of methane from dino farts would have contributed about .4 watts per meter squared (forcing), which means about 0.3 degrees C (.54 degrees F);  and the study authors put current cow farts at 1/5 of dino belchings, so by extrapolation you’re looking at about a tenth of a degree F.

*Backdate UPDATE!  A jolly and longtime science journalist who now handles science news for the University of Utah heard a bell clang in his head when he read this news.  Thus we present:

  • AP (Oct. 23, 1991) Lee Siegel: Dung shows dinosaurs produced Earth-warming gas ; Where one also reads that a skeptic from Penn State figured there's little chance there could have been enough dinosaurs to change things (skeptic, when it comes to greenhouse gases, meant something more legit in those days). The story has most of the elements one sees in the recent news. One notices with disappointment that the new paper at Current Biology does not include in its footnotes a citation of this late 20th century during the Holocene (before proclamation of the Anthropocene in many quarters) research into dinosaur dung and methanogenesis.

Grist for the Mill: Current Biology Letter ; Cell Press Press Release ;

- Charlie Petit

Comments

Thanks Charles. I am hiding behind my caveat on the question, "Perhaps I'm wrong....". Thanks for providing the confirmation that I was indeed pretty much wrong. However, I specifically wondered how much of the temperature rise can be put on this digestion-induced increment of methane. If Borenstein is correct it's about 0.1 F today.

Since you raise the matter, The Wall Street Journal news story noted that:

"Cattle belching and gas account for about 20% of U.S. methane emissions, according to the Environmental Protection Agency."

and

"By their estimate, these dinosaurs generated 520 million tons of methane each year, the same as the total amount produced today from all sources. In comparison, cattle, goats, giraffes and other such grazers that rely on microbes to aid digestion today produce between 50 million and 100 million tons of methane each year."

We also helpfully broke down the gas composition of a human fart, for purposes of comparison.

Regards,

Lee

re: your last question: my story, in the 3rd graf:

"Today cows, goats, sheep, giraffes, and other ruminants contribute to global warming by releasing as much as 50 million to 100 million metric tons of methane per year—a significant chunk of the 500 million to 600 million metric tons emitted annually, mostly due to human activity, according to the World Meteorological Organization."

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