Except that the catch with agricultural methane growth rates is that demand for beef in nations such as China is increasing rapidly, which could quite likely spark a growth in Australia’s cattle industry to meet the export demand.

It produces methane, Australia’s largest but also most under-appreciated contribution to climate change over the next few decades.

As long as Australia’s grass-fed beef cattle production does not increase, then neither should the amount of methane in the atmosphere that is attributable to it. This is because the amount of methane should be in steady state because its half-life in the atmosphere is about 8 years. In that case the greenhouse effect from this methane is not changing (while our CO2 is still accumulating).

This doesn’t mean that the methane up there is insignificant, just that as long as its rate of generation is constant and has been constant for a while, then the amount in the atmosphere from Australian grass-fed beef cattle is also constant.

I haven’t got the figures off-hand but I would guess that it’s possible that methane already emitted by Australia is currently producing more greenhouse forcing than is produced by the carbon dioxide already emitted by Australia. The difference is that the rate of growth of greenhouse forcing by CO2 is much greater than the rate of growth of greenhouse forcing by CH4.

Of course, the logical conclusion from all this is that we should stop the growth of greenhouse forcing by CO2 (and reduce it) and bring down the relatively steady level of greenhouse forcing by CH4. e.g. halving the rate of generation of CH4 by Australian grass-fed beef cattle would, after a few half-lifetimes, bring down the level of CH4 in the atmosphere attributable to it by close to half.

Because it tastes good? Is that all there is?

However, belching from farm animals happens 24/7 and maybe systems to capture at least some of this may be worthwhile trying out, especially where those animals may by farming practices be sequestered beneath architecture for some of their lives. I used the example of dairy cattle which spend around 4 hours a day near the milking shed. If this was extended to say 8 hours, then this would represent a 30% capture of their emissions and at 200 litres a day for a cow that is no small amount.

In europe, where they bring their stock indoors for the winter so that they don’t freeze to death, they are held indoors for several months at a time. Theoretically the housing for these could be altered in a way to capture the CH4 if it is possible.

Other farmed animals including pigs spend all of their days indoors and it may be feasable to redesign their enclosures to capture the methane they give off. Chickens also spend their entire lives in batteries but I am not sure they emit methane as they are not ruminant animals.

All I am suggesting is that by engineering enclosures around existing farm practices may make a difference. Covering and capturing the methane emitted above manure disposal sites eg on Dairy farms may be the simplest and cost-effective method of converting this emission into something usable and saleable. If you throw in some additional heat from a renewable source you would increase the yield of this scheme even if you don’t go in for the highly engineered solutions they have in California.

@24 thank you but if we can’t calculate WV’s forcing, how do we know the change in total forcings ?

Barry didn’t say you can’t calculate the forcing for water vapour, he just said you couldn’t do it in the same way you would for long-lived greenhouse gases.

Why don’t you read the latest IPCC report? There are, literally, hundreds of references to water vapour in it. It’s obviously a significant and complex issue that many scientists have spent years studying.

It seems to me that the important point is that water vapour is primarily not a forcing but part of a very complex system of feedback effects. One message of the IPCC report is that the big task of climate scientists is to continue to narrow down the confidence interval around the estimates of how much those feedback efects will magnify the temperature change caused by the inital forcing.

These definitions from the IPCC report might be helpful:

Climate feedback – An interaction mechanism between processes in
the climate system is called a climate feedback when the result of
an initial process triggers changes in a second process that in turn
influences the initial one. A positive feedback intensifies the original
process, and a negative feedback reduces it.

External forcing – External forcing refers to a forcing agent outside
the climate system causing a change in the climate system. Volcanic
eruptions, solar variations and anthropogenic changes in the
composition of the atmosphere and land use change are external
forcings.

The problem with the structure is that grass-fed cows should naturally spend most of their time in pasture, so you’d only capture a small percentage of the CH4 that way. Of course, every bit helps, but I really have my doubts [and I grew up on a farm that had cows].

Breeding for lower CH4 seems at least a possibilty: domestic animals area usually pretty far away from their distant ancestors, and nobody has been trying to breed lower-CH4 ruminants until just recently.

Here in California, the UC Davis folks do a lot of work on ag + climate change, or as they say, sustainable farm-to-fork

(BTW, do satellites have the accuracy to detect the total forcing over the past 25 years and do you know this accuracy ?).

@24 thank you but if we can’t calculate WV’s forcing, how do we know the change in total forcings ?
Do we assume WV’s forcing is constant, increasing or decreasing over the past 100 years ?

For the full Hansen detail see.

http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_2.pdf

Rajendra Pauchauri, Head of IPCC is giving a guest lecture on
“The impact of meat production and consumption on climate change”
in London on 8th of September.