Review of Important Article on Animal Agriculture and Climate Change
An Environment Article from

FROM Steve Kaufman, Christian Vegetarian Association
June 2021

It does appear that the people of the world need to make a choice. Which do they value more: meat from murdered animals or the viability of their grandchildren?

Sailesh Rao’s more detailed review of the topic can be found at Animal Agriculture is the Leading Cause of Climate Change (PDF).

animals and humans

Dr. Sailesh Rao has published a remarkable report in Journal of Ecological Society (2020-21, vol. 32-33, pp. 155-167). Rao’s extensive and exhaustive review of the scientific literature on climate science has revealed that animal agriculture contributes at least 87% of annual greenhouse gas emissions and is therefore, by far, the major cause of climate change. Consequently, a global move toward plant-based eating is essential for addressing the growing climate crisis. It is not exaggeration to say that, unless we act now, the killing of nonhumans will almost certainly result in the destruction of human civilization. Cutting out fossil fuels alone will not help. Surprisingly, doing so without addressing animal agriculture will actually increase global warming and augment climate change.

Rao looks at the relationship between greenhouse gas emissions due to animal agriculture and climate change using two criteria. One is to look at the annual amount of greenhouse gas emissions that should be attributed to animal agriculture emitted each year, and then adjusting for their relative greenhouse effects. For example, methane has a much greater greenhouse effect by weight compared to CO2. Complicating these calculations, emitted gasses have different half-lives in the atmosphere. Methane has a half-life of 10-12 years, while CO2 has a half-life of about 100 years (though atmospheric CO2 interacts with CO2 sinks, most notably the ocean, such that 45% of annual global CO2 emissions is added to the atmosphere).

Another, perhaps a more helpful approach is to look at radiative forcing, which is the amount of radiative power in watts per square meter of land that happens because of human-caused (anthropogenic) greenhouse gas emissions. Rao compares annual emissions from the “burning machine” of burning carbon molecules in fossil fuels, biofuels, and plants (including trees) versus the “killing machine” of animal agriculture. Annually, the burning machine contributes 0.027 W/m2 from burning carbon compounds and 0.022 W/m2 from CH4 emissions (if the effect of methane is distributed over a 20-year time-frame). However, there is 0.95 W/m2 from sulfate aerosols released by burning fossils fuels (primarily from coal and oil) that actually block sunlight and cause global cooling. Other gas emissions are relatively inconsequential, so in the short run, the “burning machine” has a net cooling effect. The reason that burning fossil fuels causes global warming is that CO2 stays in the atmosphere for hundreds of years while sulfate aerosols have a half-life of only 3-5 days. Over time, the greenhouse effect of CO2 can exceed the cooling effect of sulfate aerosols as CO2 levels rise. In the short-term, however, reducing the burning machine will tend to enhance global warming.

In contrast, the killing machine contributes 0.009 W/m2 from burning carbon compounds, 0.035 W/m2 from CH4 emissions (if calculated over a 20-year time-frame), 0.060 W/m2 from CO2 released due to land clearing for a total of 0.104 W/m2. The global warming effect of the killing machine of 0.104 W/m2 exceeds that of the burning machine of 0.049 W/m2. However, the IPCC looked at the greenhouse gas effect of methane over 100 years, which was not reasonable given methane’s much shorter half-life. The IPCC used Local Sensitivity Analysis, which focuses on local effects. Instead, Rao used the more appropriate Global Sensitivity Analysis approach, which takes into account the global impact of a given factor. As Rao discusses in his article, the IPCC’s ties with meat and dairy interests likely account for the IPCC’s analyses, which are friendly to animal agriculture industries.

It turns out that most carbon in the atmosphere has resulted from clearing of forests and other land, which has been done primarily for grazing and growing feed for animal agriculture. This has resulted in huge quantities of carbon released from plants and trees and from the soil. If this land were allowed to revert to wild forests and grasslands, a process that would take about 40 years, there would be sufficient CO2 sequestered to reduce CO2 levels to a much safer atmospheric concentration of 350 parts per million from its current level of about 420 ppm, a level that is rising at a rate of about 2.2 ppm per year. As the CO2 concentration rises, the opportunity to restore CO2 levels to 350 ppm by ending animal agriculture and allowing wild plants and trees to grow is lost. Meanwhile, if we ended burning fossil fuels right now but did nothing about animal agriculture, it will be a disaster for two reasons. First, global warming will continue due to persistent CO2 in the atmosphere and ongoing greenhouse gas emissions from animal agriculture (particularly methane). This will be particularly hazardous for humanity and the natural world, because rising global temperatures will induce positive feedback loops, such as albedo effect and release of methane due to melting of permafrost, both of which will likely make global warming accelerate indefinitely. Second, loss of the cooling effect of sulfate aerosols from burning coal and oil will promote global warming.

It is very appropriate to consider the opportunity cost of not reclaiming land being used for animal agriculture in calculations of animal agriculture’s contributions to global warming. It is analogous to “a dollar saved is a dollar earned.” Taking into account the opportunity cost due to animal agriculture’s preventing humanity from sequestering a huge amount of CO2, Rao demonstrates that animal agriculture contributes at least 87% of annual greenhouse gas emissions is at least 87%. While reducing the burning of fossil fuels by driving electric vehicles, using LED light bulbs, and other modifications helps a little bit, the only way to effectively combat climate change is to largely eliminate animal agriculture. Choosing a vegan diet certainly helps, and this is probably much more important than anything else an individual person might do to address global warming. However, for societal change to occur, we will need economic and social policies that incentivize responsible climate behavior.

What about a technological fix? Human ingenuity is impressive, but I don’t think it’s reasonable to expect technology to reverse climate change. Carbon sequestration by burying CO2 in the earth carries a high energy cost, which will tend to increase fossil fuel consumption. Seeding the stratosphere with sulfate aerosols to block sunlight will also reduce the efficiency of plant photosynthesis and reduce crop yields, and it will also reduce the efficiency of solar energy panels. It might also change weather patterns in ways that could be very deleterious for humanity and the natural world.

Many people regard adopting a largely or completely plant-based diet as too great a burden. For example, they say that they “love” meat. While a plant-based, whole food diet provides optimum health for most people, those who want the taste and texture of meat can find them in many plant-based mock meats. Further, lab-grown “cultured meat” could soon be cost-effective compared to flesh from animals. So, it does appear that the people of the world need to make a choice. Which do they value more: meat from murdered animals or the viability of their grandchildren?

Sailesh Rao’s more detailed review of the topic can be found at Animal Agriculture is the Leading Cause of Climate Change (PDF).

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