Animal Ag Is The Leading Cause Of Climate Change, Finds Study

Advances in accounting of greenhouse gas emissions shifts the bulk of responsibility for the climate crisis away from fossil fuels onto animal agriculture, according to a new analysis.

Burning fossil fuels for energy is widely accepted as the leading cause of global warming. But in a peer-reviewed paper published in Environmental Research Letters, Gerard Wedderburn-Bisshop argues that animal agriculture is actually the primary driver of climate change, responsible for 53 percent of global average temperature rise between 1750 and 2020. That equates to 0.64ºC of warming. In contrast, he claims that fossil fuels are responsible for 19 percent of warming, equating to 0.21°C.

Wedderburn-Bisshop, a former Australian government environmental scientist who is now Executive Director of World Preservation Foundation, contends that the way emissions of greenhouse gases (GHGs) are calculated, devised in the 1990s, are out of date. Applying advances in understanding of emissions gives a more accurate picture of global warming’s causes, he argues. This method reveals land use change, driven mainly by animal agriculture, to be a far bigger contributor of emissions than previously thought.

Consistent accounting

forest and river — shaiith – stock.adobe.com Growing vegetation draws down carbon

There are three advances in climate science that Wedderburn-Bisshop applies to arrive at his conclusion. First is the use of consistent carbon accounting. His paper explains that emissions accounting rules of the Intergovernmental Panel on Climate Change (IPCC) have meant that full emissions are counted for fossil fuels and all other sources, with the exception of deforestation.

When vegetation and trees regrow, they draw down carbon. This has led to emissions from human activities causing deforestation being counted partially as net emissions rather than gross emissions. Meanwhile, gross emissions are counted for burning fossil fuels. But all emissions, no matter the source, get drawn down by growing vegetation, which means they should be counted the same way, and that deforestation-causing sectors shouldn’t be credited with the free work nature is doing to absorb their emissions, says the study.

Consistent use of gross emissions accounting across sectors reveals animal agriculture, the biggest cause of land use change and deforestation, to be responsible for 19 percent more carbon than fossil fuels since 1750, according to the paper. Another paper published by Wedderburn-Bisshop in October 2024 covers this topic in more depth.

Effective Radiative Forcing and inclusive accounting

How to account for the warming potentials of different greenhouse gases, particularly carbon dioxide and methane, has been the subject of much debate. Global Warming Potential over a 100 year period (GWP100) has been the IPCC standard metric, but recently there have been efforts, pushed particularly by high-methane emitting sectors like animal agriculture, to use others such as GWP*, which accounts for the shorter lifespan of methane compared to CO2.

Instead of GWP, Wedderburn-Bisshop argues that Effective Radiative Forcing (ERF) should be used. “ERFs are the best science available on warming caused by each gas. They are calculated in very complex atmospheric and spatial models, and are fitted to observations, so they are the most accurate metric we have,” he said. Using ERF to measure the climate impact of different gases reveals that methane’s impact, understood cumulatively, has been vastly underestimated.

The third advance that changes understanding of the main sources of climate change is for all emissions, both warming and cooling, to be counted. While animal agriculture emits mostly warming gases, fossil fuels emit gases that have both warming and cooling effects. The cooling gases have masked the warming impact of CO2 emissions from fossil fuels. This inclusive accounting reveals that while fossil fuel warming accounts for 0.79°C, there is 0.59°C cooling from co-emissions. By contrast, agriculture as a whole has caused 0.86°C warming but only 0.13°C cooling.

Policy implications

“Ignoring cooling from fossil fuel burning strongly distorts the true picture of what human activities have caused global warming,” Wedderburn-Bisshop told Plant Based News. “If we account for cooling, we have a far greater understanding of what is actually happening, so we are in a far better position to develop a more effective policy response.”

Applying inclusive and consistent accounting along with ERF would mean a shift in climate policy. “Normalizing and adopting gross deforestation emissions accounting would support policies aimed at reducing deforestation and preserving forests,” writes Wedderburn-Bisshop. “Knowing that clearing and re-clearing re-release an increasing proportion of fossil carbon informs policy that destruction of forest of any age could be seen in the same way as burning coal.”

However, the break down of cooling aerosols will result in future warming from fossil fuels. For this reason, Wedderburn-Bisshop stresses the necessity of an urgent shift away from fossil fuels.

Choices to be made

Wedderburn-Bisshop’s approach disputes the long-held view that fossil fuels are the leading cause of climate change. According to the IPCC, anthropogenic carbon dioxide has contributed the most to global warming, followed by methane. The official figure from the United Nations states that animal agriculture is responsible for 14.5 percent of emissions, which is a figure still supported by many climate scientists. Another study published in 2021 put the “minimum figure” at 16.5 percent.

However, Wedderburn-Bisshop’s paper is part of an ongoing debate about how best to measure emissions and their warming impacts. The IPCC has discussed the choices that need to be made when it comes to which emissions metrics to use. In 2018, it wrote: “Some of the choices involved in metrics are scientific (e.g., type of model, and how processes are included or parameterized in the models). Choices of time frames and climate impact are policy-related and cannot be based on science alone, but can be used to analyse different approaches and policy choices.”