I don’t have much comment on this, as the press worldwide has pretty much said it all. I await the coming comparisons between, ahem, human emissions, and dinosaur emissions.
It’s another modeling extrapolation. From the article:
Scientists believe that, just as in cows, methane-producing bacteria aided the digestion of sauropods by fermenting their plant food.
”A simple mathematical model suggests that the microbes living in sauropod dinosaurs may have produced enough methane to have an important effect on the Mesozoic climate,” said study leader Dr Dave Wilkinson, from Liverpool John Moores University.
”Indeed, our calculations suggest that these dinosaurs could have produced more methane than all modern sources – both natural and man-made – put together.”
Something smells alright – the stench of extrapolation is overpowering.
It says the paper was published in Current Biology, but I can’t find it. Anyone know where to get a copy?
UPDATE: The BBC http://www.bbc.co.uk/nature/17953792
British scientists have calculated the methane output of sauropods, including the species known as Brontosaurus.
By scaling up the digestive wind of cows, they estimate that the population of dinosaurs – as a whole – produced 520 million tonnes of gas annually. They suggest the gas could have been a key factor in the warm climate 150 million years ago.
“520 million tonnes”, that’s all? That seems in error. They obviously mean 520 teragrams. (/sarc from the paper – they quote teragrams, which sounds much bigger for MSM scare stories, but I guess they needed some unit people could get their nose around)
Here’s figure 1 from the paper:
The paper itself is a marvel of weak extrapolation:
Link to excerpt of curent “Current Biology” issue, showing the full article:
Could methane produced by sauropod dinosaurs
have helped drive Mesozoic climate warmth?
David M. Wilkinson1,*, Euan G. Nisbet2, and Graeme D. Ruxton3
Mesozoic sauropods, like many modern herbivores, are likely to have
hosted microbial methanogenic symbionts for the fermentative
digestion of their plant food . Today methane from livestock is a
significant component of the global methane budget . Sauropod
methane emission would probably also have been considerable. Here,
we use a simple quantitative approach to estimate the magnitude of such
methane production and show that the production of the ‘greenhouse’
gas methane by sauropods could have been an important factor in warm
Mesozoic climates. Sauropod dinosaurs include the largest terrestrial animals known
and exhibit a distinctive body shape, featuring a small head at the end
of a very long neck. Their diversity and geographic range suggest that
sauropods may have been keystone species in many ecosystems during
the Jurassic and Cretaceous . Based in part on data from the
Late Jurassic Morrison Formation (Western USA), Farlow et al. 
estimated population densities for sauropods ranging from a few
large adult animals to a few tens of individuals per km2. Specifically,
they estimate that if dinosaurs had an endothermic, mammalian-style
metabolism, then the total abundance of these megaherbivores would
have been 11–15 animals/km2 with a total biomass density of around
42,000 kg/km2. It is, however, very unlikely that large-bodied sauropods
had metabolisms as high as predicted by the assumption of mammalian
metabolism . If instead a reptilian metabolism in assumed, then Farlow
et al.  calculate a predicted biomass density of 377,000 kg/km2.
Per Caddyshack, I think we have a new exclamation, “Oh, dinosaur farts!”
Best not to say it during a
thunderstorm climate disruption.