May 3·edited May 3Liked by Janette Barnard

Great piece Janette. I have also been advocating for GWP*, but recently have been exposed to a broader perspective on this topic.

There is a great article titled "GWP∗ is a model, not a metric" by Malte Meinshausen and Zebedee Nicholls. Where they argue (quite effectively) that GWP* is not well suited as an emission metric. I quote "Notably, for a stakeholder with high historical CH4 emissions, and somewhat lower current CH4 emissions, the waning temperature effect of the past will dominate the additional warming from current emissions. As a result, they are considered net negative in the GWP∗-framework. Yet current emissions still warm the planet compared to what would have happened without those emissions. Metrics should reflect this marginal/additional warming. Instead, GWP∗ folds the waning effect of past emissions into metric-style assessment of the impact of future emissions. While GWP∗ is well-suited to assessing the temperature effect of time-series of emissions (hence is an excellent model), it is ill-suited as an emission metric to approximate the marginal climate effect of GHG emissions from a particular year or, say, a 5 year long commitment period."

On the surface, GWP* seems like a "no-brainer", but when one starts to dig a bit deeper, there are some serious holes in the calculation. Some have attempted to address these issues Smith et al (2021) or Allen et al (2018) methods - but the problems with the model mostly still exist.

I should state, I work in the beef industry and certainly see and advocate for the scientific community (and consumer perception for that matter) to shift from the reductionist, unicentric focus on carbon, to a more holistic, systems-based, multi-metric view of beef production globally. We very much have a first-world view of the problem, and worse, 'solution' to GHG emissions in livestock production.

Another great article that expands on this is titled "Carbon myopia: The urgent need for integrated social, economic and environmental action in the livestock sector" (I won't list all 11 researchers responsible for this publication). I quote " Globally, livestock production systems exist for several reasons, many of which are critical to livelihoods. In many areas, livestock are needed to satisfy a variety of human needs. In addition to production of meat, milk, eggs, wool, hides and skin, livestock provide draught power and nutrient cycling, supporting the environmental sustainability of production Steinfeld et al., 2003). Ruminant livestock utilize non-arable land, converting fibrous and cellulosic materials into edible human protein. In many low and middle income countries (LMIC), livestock constitute the main (if not only) household capital reserve, serving as a strategic financial reserve that reduces risk and adds financial stability to the farming system (Steinfeld et al., 2003)."

It is human nature to look for a simple solution to a smoking gun. However, I feel we need to broaden our perspective on the social, economic and environmental impact of livestock production - globally (not just from our western societal view), and be open to how best to calculate its environmental impact. Rushing to GWP* on the surface appears to be a simple solution, but we need to accept it also has its issues. On the other side, viewing livestock production from only an environmental lens is dismissing the economic, and perhaps most importantly, societal impact to people and their families - especially those in LMIC.

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This was GREAT

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Fascinating! We've been measuring methane wrong.

If reducing methane emissions from cows could actually have a net cooling effect on the atmosphere long term, there should be greater incentives for doing so.

But ironically, couldn't using GWP* as a new metric actually do the opposite? By lessening the component of methane in the GWP* metric, it could reduce the incentives to lessen emissions. What's the solution?

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Have started following your blog recently, and really enjoying it. Thanks for your insights. However, I'm not sure that the basis of this post is correct. The GWP metric DOES account for how quickly gases leave the atmosphere. The base definition of GWP in several places confirms this:

- The FAO report you link to: "For short-lived greenhouse gases, such as CH4, GWP values vary significantly depending on the time horizon used. With increasing time-horizons, the relative valuation of short-lived vs long-lived gases declines, as there is an extended period over which the long-lived gas continues to exert a radiative forcing effect on the climate while the short-lived gas is no longer in the atmosphere and can no longer exert a direct radiative effect"

- The wiki entry for GWP: "GWP is 1 for CO2. For other gases it depends on the how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered."

- The EPA definition: "CH4 emitted today lasts about a decade on average, which is much less time than CO2. But CH4 also absorbs much more energy than CO2. The net effect of the shorter lifetime and higher energy absorption is reflected in the GWP."

I'm just starting to understand the difference between GWP 20/100 vs GWP*, but it is almost certainly not that one takes into account how long gases last in the atmosphere, while the other doesn't. Rather, it seems to be that the GWP values jump around for methane and nitrous oxide depending on whether you use a 20 or 100 year horizon (GWP20, GWP100, etc), and GWP* proposes an improvement by using a different unit of measure (the equivalence in terms of global mean surface temperature increase) over GWP20/100 (equivalence in terms of how much thermal radiation is absorbed over a given time).

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I enjoyed this. But I'm not convinced that implication #3 is really so 'crystal clear'. The problem I see is that there aren't two bath tubs, there's just one planet - with lots of taps running. If you can turn one of those taps down a bit wouldn't you want to do that?

I support the move to GWP*, but I don't think that gets anyone off the hook for enacting further efficiency gains (reductions in GHG per unit of output being, as you say, the best measure). Beyond the ethical and equity considerations, our consumers are already demanding it and there's some pretty sensible technologies and practices that can move us there - at least here in New Zealand there are, and we can relatively easily roll them out across our 450 cow herds (a bit harder in India with it's 3 cow herds).

Framing GWP* as some sort of excuse to not act is just wrong. My feelings are probably similar on the 'buffalo of the Great Plains' argument - you might not be ignoring the past, but you're romanticizing it to justify the status quo.

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I appreciated your 90m bison comment fyi.

I dont get how "the good old days before oil" were so good when we had massive river drinking, prairie tilling (imagine what a area looked like with a herd of 100k animals on it in spring), belching, open air composting, and river pooping animals un regulated! Seems to me they would be considered horrific by todays level.

We shall see if the decision is accepted. A lot of the climate change b/c man crew is a bit more religious than scientific often.

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