Nonetheless, a recent report from the National Research Council (which advises the government on matters of science), titled “Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements,” lent some credence to Mithloehner’s concerns about uncertainty in the IPCC’s estimate of total global emissions:
In many developed countries, uncertainties are reported to be less than 5 percent for national CO2 emissions from fossil-fuel use, which is the dominant source. With the exception of a few minor sources in the industrial sector, uncertainties are much higher for other greenhouse gases and sources and vary greatly by country. Uncertainties for the net CO2 emissions from agriculture, forestry, and other land uses and for emissions of CH4, N2O, PFCs, HFCs, CFCs, and SF6 from all sectors can be less than 25 percent in some countries and greater than 100 percent in others.
Stephen Pacala, an ecologist at Princeton University who chaired the committee that published the report on verifying emissions, couldn’t be reached to comment on the merits of Mitloehner’s and Gerber’s arguments.
[Update, 3/30: Reached today, Pacala said that we know, unequivocally, how much greenhouse gas is in, and is being added to, the atmosphere each year.
“If you use as the measure the atmospheric totals, or increase in atmospheric totals, then we know exactly what they are to within a couple percent for all these gases,” he said.
Some uncertainty comes into play when talking about the amount of certain gases that comes from anthropogenic versus natural sources, however. Take nitrous oxide. Scientists know exactly how much is in the atmosphere and that the amount is increasing steadily. “But we cannot attribute that global increase accurately to different sources, nor can we disaggregate that N2O geographically,” Pacala said. The situation is similar for methane and the so-called F-gases (HFCs, PFCs, etc.). Carbon dioxide, on the other hand, is very well understood and scientists have a firm handle and how much is being added to the atmosphere from various sources.
Because carbon dioxide accounts for slightly over three-quarters of the IPCC’s estimate of total global greenhouse-gas emissions (based on a 100-year global warming potential), that estimate is fairly reliable. Nonetheless, Pacala said, it might be better to base the relative contribution of industries like livestock on total carbon-dioxide emissions alone.
“If you really want to do people a service, you just take as a denominator something that is indisputably known, like fossil CO2 emissions,” he said. “And you say, okay, we’re going to evaluate everything relative to that. Then the uncertainty is in the thing you’re talking about – not in something else.”]
Given the availability of such information and perspective, it is unfortunate that reporters did not do more to analyze the dispute over the 18 percent figure. On the other hand, the conflict narrative isn’t ideal either, and there might be a richer story to be found in places where Mitloehner and Gerber see eye-to-eye.
For all his skepticism, Mitloehner concedes that, globally, the 18 percent may or may not be that far off. But, applied regionally, it is certainly a misleading number, he argues, and that is his main beef (pun intended) with the figure.
“In Paraguay, the contribution of livestock may be as high as 50 percent because they are clear-cutting a lot of forest, and that basically takes a unit of [greenhouse-gas] sequestration away and puts cattle, which is an emissions source, there instead. In the U.S. the contribution from livestock is only around 3 percent of the total,” Mitloehner said. “So, I don’t think that the 18 percent number is all that meaningful because it doesn’t apply regionally. It does not apply to Ethiopia, it does not apply to Paraguay, and it does not apply to the United States. Yet it’s being used in these countries [to influence policy and consumer choices].”
This is a helpful contribution. But I'm still left wondering why Dr Mitloehner is so preoccupied with the FAO's reference to the GHG emission the IPCC attributes to transport. The FAO report only mentions the comparison with transport twice from what I can see - in the summary and conclusions and only to try to put its livestock life-cycle estimate into some perspective - ie the perspective of global inventory estimates. The fact that the IPCC transport emission estimate is not a 'life-cycle' emission is irrelevant. The idea that you have to apply life-cycle assessment approach to all sectors to know what the 100% is in relation to the FAO livestock emission number seems to be rooted in misunderstanding of both the FAO livestock emission estimate and global emission estimates. Pierre Gerber from the FAO is absolutely right - totalling sector life-cycle data would lead to more than 100%. The idea too that deforestation emissions should be attributed only to the regions in which deforestation is occuring side-steps the reality of globalised food markets. Consumers of livestock products in all developed economies are 'tele-connected' to resource use across the world through markets. For example, an indirect but potent connection between demand for beef on global markets and deforestation in the Amazon is cogently reported in the literature even though little beef is exported from these regions. Unless the USA is an economic island, the same is true of US consumers, even if they don't eat beef (see the 'How Low can we go report:
http://www.murphy-bokern.com/publishedreports.html
Overall, the FAO report has stood up well to this hostile scrutiny. It aligns with more detailed and regional assessments done for the UK. To undermine it by focusing on minor aspects on the margins of the research it reports borders on mischieve.
#1 Posted by Donal Murphy-Bokern, CJR on Mon 29 Mar 2010 at 07:28 PM
Dr. Mitloehner is correct in that, because regualtory agencies are "number hungry" (i.e., they will use emission numbers in formulating environmental regulations that may or may not be accurate for a particular region) an industry - agricultural industries specifically - may be over regulated due to insufficient scientific evidence. In California, agriculture was exempt from air quality regulations until fairly recently. When brought under the regualtory umprella, the dairy industry was being regulated using a 1938 emissions study that grossly overestimated emissions from dairy animals. It was several years before new scientific data could ascertain a proper emission factor for dairies. A lazy media once again doesn't do its proper job of vetting statements and sensationalizes a story when there was no need to. The least the media should have done was contact Dr. Mitloehner to determine "where's the beef?"
#2 Posted by Ron Harben, CJR on Mon 29 Mar 2010 at 08:30 PM
The sad thing is that it's not even the beef! It's the industrial process used to create cheap beef. If instead of plowing under the prairies and using petro intensive agriculture to raise cheap subsized corn to feed cows we used intensive rotational grazing we'd likely turn beef production into a carbon negative process.
#3 Posted by Adam, CJR on Wed 31 Mar 2010 at 02:30 PM
Is livestock more than 51% of global warming?
The paper by Dr Murphy-Bokern "How Low Can We Go" examines the large impact of livestock production on the climate. Conclusion: Reducing meat consumption is good for the climate.
It was bizarre to see a piece in The Times, (Feb 12th) reporting this study which starts "Becoming a vegetarian can do more harm to the environment than continuing to eat red meat, according to a study of the impacts of meat substitutes such as tofu." This nonsense was repeated in the media across the world.
Much of livestock's impact on climate is via the methane generated. "How Low Can We Go" and "Livestock's long shadow" rate methane as 25 times Carbon Dioxide. This is the Global Warming Potential (GWP) for methane measured over 100 years. In contrast, the GWP for methane measured over 20 years is 72 times carbon dioxide.
Some scientists now believe that global warming should be slowed quickly because we need time to develop strategies for the longer term. So why not rate methane at 72 times carbon dioxide?
The biggest obstacle is not understanding the science of climate change, it is overcoming the mis-information and media nonsense such as The Times piece.
A recent paper by World Bank environmental advisors for the World Watch Institute, "Livestock and climate change" criticised "Livestock's long shadow" claiming 51% of global greenhouse emissions are caused by livestock. They used the the twenty year measure for methane (72).
No report in The Times.
P.S. A recent paper by Schindell et al. uprates methane to 105 times carbon dioxide when measured over 20 years ("Improved Attribution of Climate Forcing to Emissions", Science 30 October 2009).
So does livestock exceed even 51%?
#4 Posted by Geoff Beacon, CJR on Fri 2 Apr 2010 at 07:02 AM