How we measure the effects of methane matters for climate policy

Date:
December 14, 2021
Source:
International Institute for Applied Systems Analysis
Summary:
An international team of researchers explored how focusing either
on the short- or long-term warming effects of methane can affect
climate mitigation policies and dietary transitions in agriculture.



FULL STORY ==========================================================================
How effective is the promotion of low-meat diets at reducing greenhouse
gas emissions compared to carbon pricing when the effectiveness of
mitigation policies is measured against methane's long-term behavior? An international team of researchers explored how focusing either on
the short- or long-term warming effects of methane can affect climate mitigation policies and dietary transitions in agriculture.


========================================================================== Unlike the other main greenhouse gases (GHG) and particularly carbon
dioxide (CO2), methane (CH4) has a short atmospheric life (around
10 years). Its warming effect is significant in the short term but
diminishes in the long term. Depending on the time scale considered,
methane's contribution to agricultural emissions and climate change may
vary substantially. This has important implications in the design of
global climate change mitigation policies for agriculture.

Based on projections from three agricultural economic models, the study
just published in the journal Nature Food shows how different valuations
of methane, reflecting either a short- or long-term focus, may affect
the cost- effectiveness of mitigation policies and the benefits of
low-meat diets.

Conventionally, the climate impact of a certain sector is evaluated
through its annual greenhouse gas emissions, typically using the Global
Warming Potential over a 100 year period metric ? GWP100 ? which estimates
the change in atmospheric energy balance resulting from a particular
type of GHG emission.

However, as GHG emissions are reported as CO2-equivalents (which is a
very stable GHG), GWP100 can fail to capture how the relative impacts
of different gases change over time.

The short-lived character of methane emissions has been arguably
overlooked in most assessments of emission reductions required from the agricultural sector to achieve climate targets. The authors explored
how different valuations of methane affect the ranking of mitigation
policies in agriculture and, consequently, the sector's contribution to
global warming.

"The study highlights the importance of methane abatement options to
slow down the contribution of agriculture to global warming. Given the
short atmospheric lifetime of methane, which not only delivers climate
effects on a relatively short time horizon, but also contributes to
climate change, this makes it an interesting and essential element in agricultural mitigation policy design," explains study coauthor Stefan
Frank, a researcher in the IIASA Integrated Biosphere Futures Research
Group.

The findings indicate that mitigation policies focused on methane's
short-term impact lead to greater emission reductions and the authors
highlight that focusing specifically on the short-term effects of methane
will lead to larger reductions of emissions compared to policies that do
not consider methane's short-liveness. Such stringent mitigation policies
can even result in methane's contribution to climate change dropping below current levels (since the warming effect of methane disappears). In this respect, decreasing methane emissions have the same overall effect as
CO2 uptake or carbon capture and storage technologies.

The authors further highlight that the impact of low animal protein
diets as a mitigation option strongly depends on the context in which
it is occurring. If mitigation policies base themselves on metrics that
reflect methane's long-term behavior (resulting in a lower relative
valuation), methane emission intensity is not as greatly reduced by
technical measures. Then, low meat diets appear as a more effective
option to reduce emissions. If policies are less strict, reductions
in meat consumption and consequently production in developed economies
could therefore become an especially powerful mitigation mechanism.

"The methane specificities -- by which we mean a significant warming
effect and related mitigation potential in the short term and the
"climate neutrality" of a stable level of emissions in the long term
-- deserve distinct treatment in climate mitigation policies. This has
been also recognized in the Global Methane Pledge, announced by the US
and the EU and supported by more than 100 countries, which represents a commitment to reduce particularly global methane emissions by at least
30% from 2020 levels by 2030," says coauthor Petr Havlik, who leads the Integrated Biosphere Futures Research Group at IIASA.

A combination of innovative production-side policy measures worldwide
and dietary changes in countries with high calorie consumption per capita
could achieve the most substantial emission reduction levels, helping to significantly reverse the contribution of agriculture to global warming.

========================================================================== Story Source: Materials provided by International_Institute_for_Applied_Systems_Analysis.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ignacio Pe'rez-Domi'nguez, Agustin del Prado, Klaus Mittenzwei,
Jordan
Hristov, Stefan Frank, Andrzej Tabeau, Peter Witzke, Petr
Havlik, Hans van Meijl, John Lynch, Elke Stehfest, Guillermo
Pardo, Jesus Barreiro- Hurle, Jason F. L. Koopman, Mari'a Jose'
Sanz-Sa'nchez. Short- and long- term warming effects of methane may
affect the cost-effectiveness of mitigation policies and benefits of
low-meat diets. Nature Food, 2021; DOI: 10.1038/s43016-021-00385-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211214104238.htm

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