Thread: Why are most carbon footprint estimates for livestock products so massive? In short: because they are based on a faulty methane calculation. EAT Lancet, Starbucks, Impossible Burger etc are drastically overestimating GHG from livestock and here is why. /1 
Traditionally, the IPCC’s AR5 estimated that the global warming caused by 1 ton of livestock methane would be 28 times that of a ton of carbon dioxide. New research destroys that estimate. /2
Traditional greenhouse gas accounting ignores the impact of changing methane emission rates while grossly exaggerating the impact of steady methane emissions (like from constant cattle herds in most developed countries). /3
Climate policy has traditionally treated every tonne of methane as supposedly “equivalent” to 28 tonnes of carbon dioxide… It isn’t. /4
To find the carbon dioxide emissions that would actually have a similar impact on global temperature as methane, you need to multiply those methane emissions by 7 (not 28), and add the rate of change of methane emissions (measured in tons of methane/year), multiplied by 2100. /5
If there is no “rate of change” (i.e. the quantity of emissions by weight is constant over time) then there is a one-off impact of only 7 times the equivalent weight of CO2 (count only once – there is no accumulation as is the case for CO2 and other long-lived gases). /6
“That this formula is vastly more accurate than the traditional accounting rule is indisputable.” /7
“Even more strikingly, if an individual [cattle or sheep] herd’s methane emissions are falling by one third of one percent per year (that’s 7/2100, so the two terms cancel out) …then that herd is no longer adding to global warming.”
Professor Myles Allen (Oxford University), co-author of IPCC SR1.5.
nature.com/articles/s4161…
newsroom.co.nz/@ideasroom/201…
nature.com/articles/s4161…
newsroom.co.nz/@ideasroom/201…
