Month: August 2019
New Improved Methane Methodology.
A solution to the misrepresentations of CO2-equivalent emissions of short-lived climate pollutants under ambitious mitigation
https://www.nature.com/articles/s41612-018-0026-8
In June 2018 new research was published by International Panel on Climate Change (IPCC) scientists from Oxford Martin School, Oxford University. The research improves upon the methodology currently defining the global warming potential of different greenhouse gases.
The researchers said, “Current climate change policy suggests a ‘one-size-fits-all’ approach to dealing with emissions, but there are two distinct types of emissions. We must treat these two groups differently.” (Professor Dave Frame)
“Long-lived pollutants, like carbon dioxide, persist in the atmosphere, building up over centuries. The CO2 created by burning coal in the 18th Century is still affecting the climate today.” On the other hand, “Short-lived pollutants, like methane, disappear within a few years. Their effect on the climate is important, but very different from that of CO2.” (Dr Michelle Cain)
While cumulative carbon dioxide (CO2) emissions dominate anthropogenic warming over centuries, temperatures over the coming decades are also strongly affected by short-lived climate pollutants (SLCPs), complicating the estimation of cumulative emission budgets for ambitious mitigation goals. Using conventional Global Warming Potentials (GWPs) to convert SLCPs to “CO2-equivalent” emissions misrepresents their impact on global temperature. Here we show that peak warming under a range of mitigation scenarios is determined by a linear combination of cumulative CO2 emissions to the time of peak warming and non-CO2 radiative forcing immediately prior to that time. This may be understood by expressing aggregate non-CO2 forcing as cumulative CO2 forcing-equivalent (CO2-fe) emissions. We show further that contributions to CO2-fe emissions are well approximated by a new usage of GWP, denoted GWP*, which relates cumulative CO2 emissions to date with the current rate of emission of SLCPs. GWP* accurately indicates the impact of emissions of both long-lived and short-lived pollutants on radiative forcing and temperatures over a wide range of timescales, including under ambitious mitigation when conventional GWPs fail. Measured by GWP*, implementing the Paris Agreement would reduce the expected rate of warming in 2030 by 28% relative to a No Policy scenario. Expressing mitigation efforts in terms of their impact on future cumulative emissions aggregated using GWP* would relate them directly to contributions to future warming, better informing both burden-sharing discussions and long-term policies and measures in pursuit of ambitious global temperature goals.
Livestock: On our plates or eating at our table? A new analysis of the feed/food debate.
https://www.sciencedirect.com/science/article/abs/pii/S2211912416300013
86% of the global livestock feed intake in dry matter consists of feed materials that are not currently edible for humans
Contrary to commonly cited figures, 1 kg of meat requires 2.8 kg of human-edible feed for ruminants and 3.2 for monogastrics
Livestock consume one third of global cereal production and uses about 40% of global arable land
Livestock use 2 billion ha of grasslands, of which about 700 million could be used as cropland
Modest improvements in feed conversion ratios can prevent further expansion of arable land dedicated to feed production.
Livestock contribute to food security by supplying essential macro- and micro-nutrients, providing manure and draught power, and generating income. But they also consume food edible by humans and graze on pastures that could be used for crop production.
Livestock, especially ruminants, are often seen as poor converters of feed into food products. This paper analyses global livestock feed rations and feed conversion ratios, with specific insight on the diversity in production systems and feed materials.
Results estimate that livestock consume 6 billion tonnes of feed (dry matter) annually – including one third of global cereal production – of which 86% is made of materials that are currently not eaten by humans. In addition, soybean cakes, which production can be considered as main driver or land-use, represent 4% of the global livestock feed intake.
Producing 1 kg of boneless meat requires an average of 2.8 kg human-edible feed in ruminant systems and 3.2 kg in monogastric systems. While livestock is estimated to use 2.5 billion ha of land, modest improvements in feed use efficiency can reduce further expansion.