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FIGURE 1: ATMOSPHERIC METHANE CONCENTRATION 1983-2014

FIGURE 2: ANNUAL INCREASE IN METHANE CONCENTRATION

FIGURE 3: ANNUAL COAL PRODUCTION

FIGURE 4: ANNUAL NATURAL GAS PRODUCTION

FIGURE 5: ANNUAL OIL PRODUCTION

FIGURE 6: ANNUAL HYDRO-POWER GENERATION

FIGURE 7: ANNUAL INDEX OF ENTERIC FERMENTATION ACTIVITY

FIGURE 8: ANNUAL METHANE EMISSIONS FROM RICE CULTIVATION

FIGURE 9: MULTI-COLLINEARITY

FIGURE 10: DETRENDED CORRELATION: COAL AND NATURAL GAS

FIGURE 11: DETRENDED CORRELATION: OIL AND HYDROPOWER

FIGURE 12: DETRENDED CORRELATION: ENTERIC FERMENTATION & RICE

FIGURE 13: DETRENDED CORRELATION AT DIFFERENT METHANE LIFETIMES

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1. The so called greenhouse effect of atmospheric carbon dioxide is based on the theory that solar irradiance reaches the surface of the earth relatively unhindered but the longer wavelength radiation by the warmed surface does not escape to outer space unhindered but is absorbed by carbon dioxide and re-radiated such that much of it is returned to the surface causing the surface temperature to be higher than it would have been without this absorption effect (Anderson, 2016) (Arrhenius, 1896) (Callendar, 1938) (Tyndall, 1861). The modern version of the theory of anthropogenic global warming (AGW) holds that atmospheric CO2 is “the control knob” that determines surface temperature at an annual time scale such that there is a direct logarithmic relationship between atmospheric CO2 and surface temperature that can be expressed in the form of an Equilibrium Climate Sensitivity or ECS to compute the rise in temperature expected for a doubling of atmospheric CO2 concentration (Charney, 1979) (Hansen-Lacis, 1984) (IPCC, 2013) (Lacis, 2010) (Manabe, 1975).
2. It has been speculated since the 1930s that man’s use of fossil fuels in the industrial economy has introduced an extraneous and unnatural source of carbon dioxide that acts as a perturbation of the current account of the carbon cycle that sustains life and the climate system on the surface of the earth (Callendar, 1938) (Revelle, 1957). When consistent, accurate, and continual measurements of atmospheric CO2 uncontaminated by local conditions became available at the remote Mauna Loa station, the observed persistent and sustained increase in atmospheric CO2 year after year was interpreted as an alarming and unprecedented trend caused by man’s use of fossil fuels (Revelle, 1983) (Keeling, 1977) (Hansen, 1981) (Hansen, 1988).
3. A compound feedback relationship between atmospheric CO2 and temperature was solved with computer climate models and it is claimed that the overall ocean-atmosphere climatology is driven completely by the greenhouse effect of CO2 on surface temperature to the point that atmospheric CO2 acts as the control knob that determines surface temperature (Lacis, Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature, 2010). The greater greenhouse effect of water vapor depends directly on the amount of warming created by CO2 which does not condense out and is therefore “long lived” in the atmosphere (Lacis, 1974) (Lacis, The role of long lived greenhouse gases, 2013) (IPCC, 2014).
4. The “human cause” argument in global warming (Anthropogenic Global Warming or AGW) is that in the industrial economy, considered to have started in the nineteenth century, humans were bringing up fossil fuels from under the ground, where they had been sequestered from the carbon cycle for millions of years, and injecting that carbon into the current account of the carbon cycle. This injection of carbon is therefore an artificial and unnatural perturbation of the carbon cycle and therefore of the climate system by way of the GHG effect of atmospheric CO2. However, this narrow definition later became extended to all human activity to include land use, agriculture, deforestation, and other activities such that the initial argument about the perturbation of the current account of the carbon cycle with external carbon no longer applied so that any carbon emission that can be ascribed to humans were considered “external”. Here we argue that this extension of a theory about the impact of the “industrial economy” on climate to all human activities, even those that predate the Industrial Revolution, is arbitrary and capricious and that the perturbation of the current account of the carbon cycle by “external carbon” can only be assessed in terms of non-surface phenomena that are peculiar to the industrial economy.
5. Two non-industrial human activities identified as additional causes of global warming are rice farming and enteric fermentation of farm animals because these activities are known to be sources of methane emissions. Methane (CH4) is considered to be a powerful greenhouse gas more potent than CO2. It has been suggested that the rate of global warming can be moderated by restricting human activities known to be sources of methane emission. A significant body of research exists on the subject of human-induced CH4 emissions from land use changes, rice farming, and cattle ranching (Conrad, 1996) (Johnson K. , 1995) (Sass, 1991) (Lamb, 1994) as well as emissions from the extraction and transportation of hydrocarbons (Harrison, 1996) (EPA, 2015) (Warmuzinski, 2008) (Allen, 2013) (Howarth, 2011). Recently, the generation of hydroelectric power, ordinarily thought to be a green energy source, has been found to be a source of anthropogenic methane because its production involves converting flowing river water into still water in reservoirs that retain the vast quantities of vegetation that were flooded when the reservoir was formed. Such bog-like conditions are known to favor methane emissions and these emissions have been documented (Fearnside, 2015) (Giles, 2006) (Magill, 2014) (Santos, 2006) (Delsontro, 2010). However, the IPCC does not yet recognize hydropower production as a source of anthropogenic methane. The IPCC identifies large flows of methane from natural sources (IPCC, 2007) (IPCC, 2014) that include mud volcanoes (Etiope, 2005), geothermal vents (Etiope G. , 2007), marine and terrestrial hydrocarbon seepage (Cline, 1977) (Geyer, 1973) (NASA/Goddard Space Flight Center, 2000) (Kvenvolden, 2003), termites (Sanderson, 1996), incomplete combustion in peat bog fires and coal seam fires (Stracher, 2004) (Kuenzer, 2007), and the wetlands of the northern hemisphere (Christensen, 2003) (Aselmann, 1989) (Ortiz-Llorente, 2012) (Bousquet, 2006). That natural sources of geological carbon are not trivial can be seen in the Pliocene-Eocene Thermal Maximum  (PETM) event when a global and catastrophic devastation is thought to have been caused by natural geological sources of methane [LINK] . A source of bias in the environmental sciences is the tendency to assume a human cause for all observed trends. 
6. Although it is common to ascribe changes in atmospheric methane to human causes under study (Smith 2010), these natural flows make that attribution problematic. An added complexity in the study of atmospheric methane is that methane is unstable in the presence of oxygen and spontaneously oxidizes to carbon dioxide and water releasing the heat of reaction into the atmosphere. Methane emissions into the atmosphere thus deplete naturally with a half life of ≈5 to 6 years. In that sense methane is not a “long-lived” greenhouse gas.
7. Care must be taken in the attribution of observed changes in atmospheric methane so that the attribution is supported by responsiveness at an annual time scale. Direct measurements of atmospheric CH4 are available from the NOAA Mauna Loa (MLO) measuring station from 1983 denominated as parts per billion by volume on a dry basis (PPBV) (NOAA, 2015). Monthly mean values of “flask” measurements of CH4 are downloaded and converted into annual means as the average of the monthly values for all 12 months of each calendar year. Annual changes in atmospheric methane are computed from 1984 to 2013 by subtracting the previous year’s annual mean adjusted for oxidation decay from the annual mean value of the current year. For the base case, we assume that each year 1/12th of the atmospheric methane decays by oxidation. Two alternate cases are also studied – one at a higher decay rate of 1/9th per year and one at a lower decay rate of 1/15th per year. These decay rates are based on a mean lifetime of methane in the atmosphere of 12±3 years. These differences give us 30 years of changes in mean annual atmospheric CH4. This time series is the object of our study and the dependent variable in our detrended correlation model.
8. Methane measurements have been made at MLO using the “in-situ” method since 1988 (NOAA, 2015). These values are somewhat different. The flask measurements are used in this study because they offer a longer time series and a larger sample size. In the common period 1988-2014, the two series do not differ in a way that would affect our analysis. A comprehensive dataset of global greenhouse gas emissions from agricultural activities is available from the FAOSTAT data services of the Food and Agriculture Organization of the United Nations (FAO, 2015). The data are reported as “CO2-equivalent” emissions in Gigagrams per year. These figures are used only as a proxy for year to year changes in the size of agricultural activities and processes that are known to be sources of methane emission. Agricultural activities included in this study are enteric fermentation and rice cultivation.
9. Figure 1 shows the atmospheric CH4 data used in this study. These data are used to compute annual change in atmospheric CH4 net of oxidation decay shown in the left panel of Figure 2.  The changes are computed as δCH4 = CH4i – CH4i-1 * (λ-1)/λ where λ is the mean lifetime of methane in the atmosphere and i is the year for which the change is computed. The difference δCH4 represents the additional methane that was added to the atmosphere from surface sources during the year. In the base  case presented here, the value of λ is set to λ=12 years. Possible values of λ at either end of the range  are also included in this study with λ=9 years and λ=15 years.
10. The values of δCH4 are detrended by subtracting the trend line from the observed values. The detrended series is shown in the right panel of Figure 2. These values are the object of our study. They represent the year to year changes in atmospheric CH4 net of long term trends. We proceed now to investigate whether these changes correlate with indexes of six human activities that have been identified as anthropogenic sources of atmospheric methane. The observed data and their detrended values for coal production, natural gas production, oil production, hydropower generation, enteric fermentation, and rice cultivation are presented graphically in Figure 3 to Figure 8. An important feature of the six detrended series presented here is that, with the exception of oil production, the explanatory variables are correlated with each other to a degree that makes it difficult to test their individual effects in the same model (Draper&Smith, 1998). The correlation coefficients among the six anthropogenic emission factors are tabulated in Figure 9. The multi-collinearity among the anthropogenic emission rates may imply that methane emissions attributed to these anthropogenic sources may derive from a common natural source source and that their attribution is arbitrary and capricious.
11. In detrended correlation analysis, we look at the correlation of each of the detrended sources of emission individually with the detrended δCh4 series. The six correlations are shown graphically in Figure 10 to Figure 12. The correlations shown in these figures are based on a mean methane lifetime in the atmosphere of λ= 12 years and the assumption that 1/12th of the atmospheric methane is removed by oxidation each year. Figure 13 shows the correlations at two additional decay rates with λ=9 and λ=15. We note in Figure 13 that higher values of λ and the corresponding lower rates of decay of atmospheric methane yield higher correlations. All eighteen values of detrended correlations are tabulated in Figure 13. The correlations for enteric fermentation and coal production are higher than the correlations for the other emission factors but in all eighteen hypothesis tests the p-value > α and we fail to reject the null H0: ρ≤0. The data do not provide evidence that any of the six sources of anthropogenic methane emission are correlated with changes in atmospheric methane at an annual time scale net of long term trends. The data do not provide evidence that changes in atmospheric methane concentration can be explained in terms of the six anthropogenic causes investigated. Rather their multi-collinearity suggests that changes in methane derive from a common source possibly the geological sources listed by the IPCC and arbitrarily ascribed to human activities.
12. Using a conversion rate of 2.78 megatons per ppbv of methane in the atmosphere we estimate that annual changes in atmospheric methane in the sample period corresponded with 320-360 MTY for a lifetime of λ=15 years, 400-440 MTY for λ=12 years, and 540-585 MTY for λ=9 years. The IPCC estimates natural flows as 254-502 MTY and anthropogenic flows as 278-239 MTY. The detrended correlation of annual changes in atmospheric methane with anthropogenic sources were highest at λ=15 years when they are least needed and lowest at λ=9 years when they are most needed to achieve a methane balance. The apparent paradox provides further support for the non-significance and spuriousness of the observed sample correlations. The role of anthropogenic sources in observed changes in atmospheric methane will likely not be understood until we have gained a far better precision in the measurement of natural flows (Bousquet, 2006) (Talbot, 2014).
13. We conclude from these findings that anthropogenic activities do not contribute to the observed rise in atmospheric methane in a measurable way and that therefore proposed climate action initiatives of eating less meat, the banning of fracking for natural gas production, and proposed changes in rice cultivation are unnecessary because there is no evidence that these initiatives will change the rate of increase in atmospheric methane. It  is far more likely that the observed rising trend in atmospheric methane is natural and geological in origin with no scope for human intervention for its attenuation. 

BIBLIOGRAPHY

CATTLE, MEAT EATING, METHANE, AND CLIMATE CHANGE

1. 1991: Fung, Inez, et al. “Three‐dimensional model synthesis of the global methane cycle.” Journal of Geophysical Research: Atmospheres 96.D7 (1991): 13033-13065. The geographic and seasonal emission distributions of the major sources and sinks of atmospheric methane were compiled using methane flux measurements and energy and agricultural statistics in conjunction with global digital data bases of land surface characteristics and anthropogenic activities. Chemical destruction of methane in the atmosphere was calculated using three‐dimensional OH fields every 5 days taken from Spivakovsky et al. (1990a, b). The signatures of each of the sources and sinks in the atmosphere were simulated using a global three‐dimensional tracer transport model. Candidate methane budget scenarios were constructed according to mass balance of methane and its carbon isotopes. The verisimilitude of the scenarios was tested by their ability to reproduce the meridional gradient and seasonal variations of methane observed in the atmosphere. Constraints imposed by all the atmospheric observations are satisfied simultaneously by several budget scenarios. A preferred budget comprises annual destruction rates of 450 Tg by OH oxidation and 10 Tg by soil absorption and annual emissions of 80 Tg from fossil sources, 80 Tg from domestic animals, and 35 Tg from wetlands and tundra poleward of 50°N. Emissions from landfills, tropical swamps, rice fields, biomass burning, and termites total 295 Tg; however, the individual contributions of these terms cannot be determined uniquely because of the lack of measurements of direct fluxes and of atmospheric methane variations in regions where these sources are concentrated.
   
2. 1997: Hein, Ralf, Paul J. Crutzen, and Martin Heimann. “An inverse modeling approach to investigate the global atmospheric methane cycle.” Global Biogeochemical Cycles 11.1 (1997): 43-76. Estimates of the global magnitude of atmospheric methane sources are currently mainly based on direct flux measurements in source regions. Their extrapolation to the entire globe often involves large uncertainties. In this paper, we present an inverse modeling approach which can be used to deduce information on methane sources and sinks from the temporal and spatial variations of atmospheric methane mixing ratios. Our approach is based on a three‐dimensional atmospheric transport model which, combined with a tropospheric background chemistry module, is also employed to calculate the global distribution of OH radicals which provide the main sink for atmospheric methane. The global mean concentration of OH radicals is validated with methyl chloroform (CH₃CCl₃) observations. The inverse modeling method optimizes the agreement between model‐calculated and observed methane mixing ratios by adjusting the magnitudes of the various methane sources and sinks. The adjustment is constrained by specified a priori estimates and uncertainties of the source and sink magnitudes. We also include data on the ¹³C/¹²C isotope ratio of atmospheric methane and its sources in the model. Focusing on the 1980s, two scenarios of global methane sources are constructed which reproduce the main features seen in the National Oceanic and Atmospheric Administration’s Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL) methane observations. Differences between these two scenarios may probably be attributed to underestimated a priori uncertainties of wetland emissions. Applying the inverse model, the average uncertainty of methane source magnitudes could be reduced by at least one third. We also examined the decrease in the atmospheric methane growth rate during the early 1990s but could not associate it with changes in specific sources.   [FULL TEXT PDF]
3. 1998: Dlugokencky, E. J., et al. “Continuing decline in the growth rate of the atmospheric methane burden.” Nature 393.6684 (1998): 447. The global atmospheric methane burden has more than doubled since pre-industrial times¹,², and this increase is responsible for about 20% of the estimated change in direct radiative forcing due to anthropogenic greenhouse-gas emissions. Research into future climate change and the development of remedial environmental policies therefore require a reliable assessment of the long-term growth rate in the atmospheric methane load. Measurements have revealed that although the global atmospheric methane burden continues to increase² with significant interannual variability³,⁴, the overall rate of increase has slowed²,⁵. Here we present an analysis of methane measurements from a global air sampling network that suggests that, assuming constant OH concentration, global annual methane emissions have remained nearly constant during the period 1984–96, and that the decreasing growth rate in atmospheric methane reflects the approach to a steady state on a timescale comparable to methane’s atmospheric lifetime. If the global methane sources and OH concentration continue to remain constant, we expect average methane mixing ratios to increase slowly from today’s 1,730 nmol mol⁻¹ to ∼1,800 nmol mol⁻¹, with little change in the contribution of methane to the greenhouse effect.
4. 1998: Etheridge, David M., et al. “Atmospheric methane between 1000 AD and present: Evidence of anthropogenic emissions and climatic variability.” Journal of Geophysical Research: Atmospheres 103.D13 (1998): 15979-15993. Atmospheric methane mixing ratios from 1000 A.D. to present are measured in three Antarctic ice cores, two Greenland ice cores, the Antarctic firn layer, and archived air from Tasmania, Australia. The record is unified by using the same measurement procedure and calibration scale for all samples and by ensuring high age resolution and accuracy of the ice core and firn air. In this way, methane mixing ratios, growth rates, and interpolar differences are accurately determined. From 1000 to 1800 A.D. the global mean methane mixing ratio averaged 695 ppb and varied about 40 ppb, contemporaneous with climatic variations. Interpolar (N‐S) differences varied between 24 and 58 ppb. The industrial period is marked by high methane growth rates from 1945 to 1990, peaking at about 17 ppb yr⁻¹ in 1981 and decreasing significantly since. We calculate an average total methane source of 250 Tg yr⁻¹ for 1000–1800 A.D., reaching near stabilization at about 560 Tg yr⁻¹ in the 1980s and 1990s. The isotopic ratio, δ¹³CH₄, measured in the archived air and firn air, increased since 1978 but the rate of increase slowed in the mid‐1980s. The combined CH₄ and δ¹³CH₄ trends support the stabilization of the total CH₄ source.  [FULL TEXT PDF]
5. 1998: Lelieveld, J. O. S., Paul J. Crutzen, and Frank J. Dentener. “Changing concentration, lifetime and climate forcing of atmospheric methane.” Tellus B 50.2 (1998): 128-150. Previous studies on ice core analyses and recent in situ measurements have shown that CH₄ has increased from about 0.75–1.73 μmol/mol during the past 150 years. Here, we review sources and sink estimates and we present global 3D model calculations, showing that the main features of the global CH₄ distribution are well represented. The model has been used to derive the total CH₄ emission source, being about 600 Tg yr^‐1. Based on published results of isotope measurements the total contribution of fossil fuel related CH₄ emissions has been estimated to be about 110 Tg yr^‐1. However, the individual coal, natural gas and oil associated CH₄ emissions can not be accurately quantified. In particular natural gas and oil associated emissions remain speculative. Since the total anthropogenic CH₄ source is about 410 Tg yr^‐1 (∼70% of the total source) and the mean recent atmospheric CH₄ increase is ∼20 Tg yr^‐1 an anthropogenic source reduction of 5% could stabilize the atmospheric CH₄ level. We have calculated the indirect chemical effects of increasing CH₄ on climate forcing on the basis of global 3D chemistry‐transport and radiative transfer calculations. These indicate an enhancement of the direct radiative effect by about 30%, in agreement with previous work. The contribution of CH₄ (direct and indirect effects) to climate forcing during the past 150 years is 0.57W m⁻² (direct 0.44W m⁻², indirect 0.13 W m⁻²). This is about 35% of the climate forcing by CO₂ (1.6W m⁻²) and about 22% of the forcing by all long‐lived greenhouse gases (2.6 W m⁻²). Scenario calculations (IPCC‐IS92a) indicate that the CH₄ lifetime in the atmosphere increased by about 25–30%during the past 150 years to a current value of 7.9 years. Future lifetime changes are expected to be much smaller, about 6%, mostly due to the expected increase of tropospheric O₃ (→OH) in the tropics. The global mean concentration of CH₄ may increase to about 2.55 μmol/mol, its lifetime is expected to increase to 8.4 years in the year 2050. Further, we have calculated a CH₄ global warming potential (GWP) of 21 (kgCH₄/kgCO₂) over a time horizon of 100 years, in agreement with IPCC (1996). Scenario calculations indicate that the importance of the climate forcing by CH₄ (including indirect effects) relative to that of CO₂ will decrease in future; currently this is about 35%, while this is expected to decrease to about 15% in the year 2050. [FULL TEXT PDF]  
   
6. 1999: Houweling, Sander, et al. “Inverse modeling of methane sources and sinks using the adjoint of a global transport model.” Journal of Geophysical Research: Atmospheres104.D21 (1999): 26137-26160. An inverse modeling method is presented to evaluate the sources and sinks of atmospheric methane. An adjoint version of a global transport model has been used to estimate these fluxes at a relatively high spatial and temporal resolution. Measurements from 34 monitoring stations and 11 locations along two ship cruises by the National Oceanographic and Atmospheric Administration have been used as input. Recent estimates of methane sources, including a number of minor ones, have been used as a priori constraints. For the target period 1993–1995 our inversion reduces the a priori assumed global methane emissions of 528 to 505 Tg(CH₄) yr⁻¹ a posteriori. Further, the relative contribution of the Northern Hemispheric sources decreases from 77% a priori to 67% a posteriori. In addition to making the emission estimate more consistent with the measurements, the inversion helps to reduce the uncertainties in the sources. Uncertainty reductions vary from 75% on the global scale to ∼1% on the grid‐scale (8° × 10°), indicating that the grid scale variability is not resolved by the measurements. Large scale features such as the inter-hemispheric methane concentration gradient are relatively well resolved and therefore impose strong constraints on the estimated fluxes. The capability of the model to reproduce this gradient is critically dependent on the accuracy at which the inter-hemispheric tracer exchange and the large‐scale hydroxyl radical distribution are represented. As a consequence, the inversion‐derived emission estimates are sensitive to errors in the transport model and the calculated hydroxyl radical distribution. In fact, a considerable contribution of these model errors cannot be ignored. This underscores that source quantification by inverse modeling is limited by the extent to which the rate of interhemispheric transport and the hydroxyl radical distribution can be validated. We show that the use of temporal and spatial correlations of emissions may significantly improve our results; however, at present the experimental support for such correlations is lacking. Our results further indicate that uncertainty reductions reported in previous inverse studies of methane have been overestimated.  [FULL TEXT PDF] 
7. 2003: Dlugokencky, E. J., et al. “Atmospheric methane levels off: Temporary pause or a new steady‐state?.” Geophysical Research Letters 30.19 (2003).  The globally‐averaged atmospheric methane abundance determined from an extensive network of surface air sampling sites was constant at ∼1751 ppb from 1999 through 2002. Assuming that the methane lifetime has been constant, this implies that during this 4‐year period the global methane budget has been at steady state. We also observed a significant decrease in the difference between northern and southern polar zonal annual averages of CH₄ from 1991 to 1992. Using a 3‐D transport model, we show that this change is consistent with a decrease in CH₄ emissions of ∼10 Tg CH₄ from north of 50°N in the early‐1990s. This decrease in emissions may have accelerated the global methane budget towards steady state. Based on current knowledge of the global methane budget and how it has changed with time, it is not possible to tell if the atmospheric methane burden has peaked, or if we are only observing a persistent, but temporary pause in its increase.  [FULL TEXT]
8. 2010: Smith, Pete, David Reay, and Andre Van Amstel, eds. Methane and climate change. Routledge, 2010.  It is necessary to minimize our environmental impacts and carbon footprint through reducing waste, recycling and offsetting our methane emissions. During the 1990s and the first few years of the 21st century the growth rate of CH4 concentrations in the atmosphere slowed to almost zero, but during 2007 and 2008 concentrations increased once again. Recent studies have attributed to enhanced emissions of CH4 in the Arctic as a result of high temperatures in 2007, and to greater rainfall in the tropics in 2008. The former response represents a snapshot of a potentially very large positive climate change feedback, with the higher temperatures projected at high latitudes for the 21st century increasing CH4 emissions from wetlands, permafrost and CH4 hydrates. It is to this and the myriad of other natural and anthropogenic determinants of CH4 flux to the atmosphere that this book is directed. [FULL TEXT PDF]
9. 2010: Popp, Alexander, Hermann Lotze-Campen, and Benjamin Bodirsky. “Food consumption, diet shifts and associated non-CO2 greenhouse gases from agricultural production.” Global Environmental Change 20.3 (2010): 451-462. Today, the agricultural sector accounts for approximately 15% of total global anthropogenic emissions, mainly methane and nitrous oxide. Projecting the future development of agricultural non-CO₂ greenhouse gas (GHG) emissions is important to assess their impacts on the climate system but poses many problems as future demand of agricultural products is highly uncertain. We developed a global land use model (MAgPIE) that is suited to assess future anthropogenic agricultural non-CO₂ GHG emissions from various agricultural activities by combining socio-economic information on population, income, food demand, and production costs with spatially explicit environmental data on potential crop yields. In this article we describe how agricultural non-CO₂ GHG emissions are implemented within MAgPIE and compare our simulation results with other studies. Furthermore, we apply the model up to 2055 to assess the impact of future changes in food consumption and diet shifts, but also of technological mitigation options on agricultural non-CO₂ GHG emissions. As a result, we found that global agricultural non-CO₂ emissions increase significantly until 2055 if food energy consumption and diet preferences remain constant at the level of 1995. Non-CO₂ GHG emissions will rise even more if increasing food energy consumption and changing dietary preferences towards higher value foods, like meat and milk, with increasing income are taken into account. In contrast, under a scenario of reduced meat consumption, non-CO₂GHG emissions would decrease even compared to 1995. Technological mitigation options in the agricultural sector have also the capability of decreasing non-CO₂ GHG emissions significantly. However, these technological mitigation options are not as effective as changes in food consumption. Highest reduction potentials will be achieved by a combination of both approaches.  [FULL TEXT PDF]
10. 2011: Wirsenius, Stefan, Fredrik Hedenus, and Kristina Mohlin. “Greenhouse gas taxes on animal food products: rationale, tax scheme and climate mitigation effects.” Climatic change108.1-2 (2011): 159-184. Agriculture is responsible for 25–30% of global anthropogenic greenhouse gas (GHG) emissions but has thus far been largely exempted from climate policies. Because of high monitoring costs and comparatively low technical potential for emission reductions in the agricultural sector, output taxes on emission-intensive agricultural goods may be an efficient policy instrument to deal with agricultural GHG emissions. In this study we assess the emission mitigation potential of GHG weighted consumption taxes on animal food products in the EU. We also estimate the decrease in agricultural land area through the related changes in food production and the additional mitigation potential in devoting this land to bioenergy production. Estimates are based on a model of food consumption and the related land use and GHG emissions in the EU. Results indicate that agricultural emissions in the EU27 can be reduced by approximately 32 million tons of CO₂-eq with a GHG weighted tax on animal food products corresponding to €60 per ton CO₂-eq. The effect of the tax is estimated to be six times higher if lignocellulosic crops are grown on the land made available and used to substitute for coal in power generation. Most of the effect of a GHG weighted tax on animal food can be captured by taxing the consumption of ruminant meat alone.
11. 2013: Ripple, William J., et al. “Ruminants, climate change and climate policy.” Nature Climate Change 4.1 (2013): 2. Greenhouse gas emissions from ruminant meat production are significant. Reductions in global ruminant numbers could make a substantial contribution to climate change mitigation goals and yield important social and environmental co-benefits.International climate negotiators can take steps to reduce greenhouse gas emissions from livestock as well as from the burning of fossil fuels. So far, global climate policy instruments have mainly focused on engineering improved industrial processes, energy efficiency and investments in alternative energy generation technologies, because sustainability has been predominantly interpreted as technological progress rather than changed patterns of human behaviour. Continued growth of ruminant meat consumption will represent a major obstacle for reaching ambitious climate change targets. The substantial environmental and climate costs of increased meat consumption have been recognized by the United Nations Food and Agriculture Organization. However, mitigation of greenhouse gas emissions from ruminants has not received adequate attention in negotiations under the United Nations Framework Convention on Climate Change. Meeting documents show that activities to reduce emissions from ruminants and agriculture in general, and in negotiations on land use, land-use change and forestry and reducing emission from deforestation and forest degradation have been disproportionately slow. The land-use accounting under the Kyoto Protocol provides insufficient coverage of land-based emissions considering their large contributions to greenhouse gas fluxes. The Kyoto Protocol also only covers industrialized countries, so it misses some of the largest emerging ruminant producers. Further, under Articles 3.3 and 3.4 of the Kyoto Protocol, emission reduction commitments for cropland and grazing land management are optional in many situations. The above-presented evidence calls for a more comprehensive approach to accounting in the Agriculture, Forestry and Other Land Use sector, following the lead of those countries requesting mandatory accounting for land-based emissions, including cropland and grazing land sectors. Progress would be facilitated if emissions resulting from ruminant livestock production are placed on the agenda of forthcoming global climate meetings such as the annual sessions of the Conference of the Parties. Current national policies on mitigating climate change could also be revised to curtail emissions from ruminant livestock in both developed and developing countries. Because the Earth’s climate may be near tipping points to major change, the need to act is increasingly pressing. Lowering peak climate forcing quickly with ruminant and CH4 reductions would lessen the likelihood of irreversibly crossing such tipping points into a new climatic state. Reducing the numbers of ruminants will be a difficult and complex task, both politically and socially. However, decreasing ruminants should be considered alongside our grand challenge of significantly reducing the world’s reliance on fossil fuel combustion. Only with the recognition of the urgency of this issue and the political will to commit resources to comprehensively mitigate both CO2 and non-CO2 greenhouse gas emissions will meaningful progress be made on climate change. For an effective and rapid response, we need to increase awareness among the public and policymakers that what we choose to eat has important consequences for climate change.   [FULL TEXT PDF]
12. 2013: Edjabou, Louise Dyhr, and Sinne Smed. “The effect of using consumption taxes on foods to promote climate friendly diets–The case of Denmark.” Food policy 39 (2013): 84-96. Agriculture is responsible for 17–35% of global anthropogenic greenhouse gas emissions with livestock production contributing by approximately 18–22% of global emissions. Due to high monitoring costs and low technical potential for emission reductions, a tax on consumption may be a more efficient policy instrument to decrease emissions from agriculture than a tax based directly on emissions from production. In this study, we look at the effect of internalising the social costs of greenhouse gas emissions through a tax based on CO₂equivalents for 23 different foods. Furthermore, we compare the loss in consumer surplus and the changed dietary composition for different taxation scenarios. In the most efficient scenario, we find a decrease in the carbon footprint from foods for an average household of 2.3–8.8% at a cost of 0.15–1.73 DKK per kg CO₂ equivalent whereas the most effective scenario led to a decrease in the carbon footprint of 10.4–19.4%, but at a cost of 3.53–6.90 DKK per kg CO₂ equivalent. The derived consequences for health show that scenarios where consumers are not compensated for the increase in taxation level lead to a decrease in the total daily amount of kJ consumed, whereas scenarios where the consumers are compensated lead to an increase. Most scenarios lead to a decrease in the consumption of saturated fat. Compensated scenarios leads to an increase in the consumption of added sugar, whereas uncompensated scenarios lead to almost no change or a decrease. Generally, the results show a low cost potential for using consumption taxes to promote climate friendly diets. HIGHLIGHTS: Effect of a consumption tax based on CO₂ equivalents for 23 different foods. Calculated changes in consumption based on systems of demand elasticities, The most efficient scenario decreases CO₂ emission with 2.3–8.8% at a cost of 0.15–1.73 DKK/kilo, Health effects in terms of changes in the intake of calories, saturated fat and sugar. CONCLUSION: Taxes are a low cost way of promoting climate friendly diets without large adverse health effects. [FULL TEXT PDF]
13. 2014: Hedenus, Fredrik, Stefan Wirsenius, and Daniel JA Johansson. “The importance of reduced meat and dairy consumption for meeting stringent climate change targets.” Climatic change 124.1-2 (2014): 79-91. For agriculture, there are three major options for mitigating greenhouse gas (GHG) emissions: 1) productivity improvements, particularly in the livestock sector; 2) dedicated technical mitigation measures; and 3) human dietary changes. The aim of the paper is to estimate long-term agricultural GHG emissions, under different mitigation scenarios, and to relate them to the emissions space compatible with the 2 °C temperature target. Our estimates include emissions up to 2070 from agricultural soils, manure management, enteric fermentation and paddy rice fields, and are based on IPCC Tier 2 methodology. We find that baseline agricultural CO₂-equivalent emissions (using Global Warming Potentials with a 100 year time horizon) will be approximately 13 Gton CO₂eq/year in 2070, compared to 7.1 Gton CO₂eq/year 2000. However, if faster growth in livestock productivity is combined with dedicated technical mitigation measures, emissions may be kept to 7.7 Gton CO₂eq/year in 2070. If structural changes in human diets are included, emissions may be reduced further, to 3–5 Gton CO₂eq/year in 2070. The total annual emissions for meeting the 2 °C target with a chance above 50 % is in the order of 13 Gton CO₂eq/year or less in 2070, for all sectors combined. We conclude that reduced ruminant meat and dairy consumption will be indispensable for reaching the 2 °C target with a high probability, unless unprecedented advances in technology take place.
14. 2014: Caulton, Dana R., et al. “Toward a better understanding and quantification of methane emissions from shale gas development.” Proceedings of the National Academy of Sciences (2014): 201316546. The identification and quantification of methane emissions from natural gas production has become increasingly important owing to the increase in the natural gas component of the energy sector. An instrumented aircraft platform was used to identify large sources of methane and quantify emission rates in southwestern PA in June 2012. A large regional flux, 2.0–14 g CH₄ s⁻¹ km⁻², was quantified for a ∼2,800-km² area, which did not differ statistically from a bottom-up inventory, 2.3–4.6 g CH₄ s⁻¹ km⁻². Large emissions averaging 34 g CH₄/s per well were observed from seven well pads determined to be in the drilling phase, 2 to 3 orders of magnitude greater than US Environmental Protection Agency estimates for this operational phase. The emissions from these well pads, representing ∼1% of the total number of wells, account for 4–30% of the observed regional flux. More work is needed to determine all of the sources of methane emissions from natural gas production, to ascertain why these emissions occur and to evaluate their climate and atmospheric chemistry impacts.
15. 2014: Bajželj, Bojana, et al. “Importance of food-demand management for climate mitigation.” Nature Climate Change4.10 (2014): 924. Recent studies show that current trends in yield improvement will not be sufficient to meet projected global food demand in 2050, and suggest that a further expansion of agricultural area will be required. However, agriculture is the main driver of losses of biodiversity and a major contributor to climate change and pollution, and so further expansion is undesirable. The usual proposed alternative—intensification with increased resource use—also has negative effects. It is therefore imperative to find ways to achieve global food security without expanding crop or pastureland and without increasing greenhouse gas emissions. Some authors have emphasized a role for sustainable intensification in closing global ‘yield gaps’ between the currently realized and potentially achievable yields. However, in this paper we use a transparent, data-driven model, to show that even if yield gaps are closed, the projected demand will drive further agricultural expansion. There are, however, options for reduction on the demand side that are rarely considered. In the second part of this paper we quantify the potential for demand-side mitigation options, and show that improved diets and decreases in food waste are essential to deliver emissions reductions, and to provide global food security in 2050. [FULL TEXT PDF]
16. 2014: Westhoek, Henk, et al. “Food choices, health and environment: effects of cutting Europe’s meat and dairy intake.” Global Environmental Change 26 (2014): 196-205. Western diets are characterised by a high intake of meat, dairy products and eggs, causing an intake of saturated fat and red meat in quantities that exceed dietary recommendations. The associated livestock production requires large areas of land and lead to high nitrogen and greenhouse gas emission levels. Although several studies have examined the potential impact of dietary changes on greenhouse gas emissions and land use, those on health, the agricultural system and other environmental aspects (such as nitrogen emissions) have only been studied to a limited extent. By using biophysical models and methods, we examined the large-scale consequences in the European Union of replacing 25–50% of animal-derived foods with plant-based foods on a dietary energy basis, assuming corresponding changes in production. We tested the effects of these alternative diets and found that halving the consumption of meat, dairy products and eggs in the European Union would achieve a 40% reduction in nitrogen emissions, 25–40% reduction in greenhouse gas emissions and 23% per capita less use of cropland for food production. In addition, the dietary changes would also lower health risks. The European Union would become a net exporter of cereals, while the use of soymeal would be reduced by 75%. The nitrogen use efficiency (NUE) of the food system would increase from the current 18% to between 41% and 47%, depending on choices made regarding land use. As agriculture is the major source of nitrogen pollution, this is expected to result in a significant improvement in both air and water quality in the EU. The resulting 40% reduction in the intake of saturated fat would lead to a reduction in cardiovascular mortality. These diet-led changes in food production patterns would have a large economic impact on livestock farmers and associated supply-chain actors, such as the feed industry and meat-processing sector.
17. 2014: Scarborough, Peter, et al. “Dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK.” Climatic change 125.2 (2014): 179-192. The production of animal-based foods is associated with higher greenhouse gas (GHG) emissions than plant-based foods. The objective of this study was to estimate the difference in dietary GHG emissions between self-selected meat-eaters, fish-eaters, vegetarians and vegans in the UK. Subjects were participants in the EPIC-Oxford cohort study. The diets of 2,041 vegans, 15,751 vegetarians, 8,123 fish-eaters and 29,589 meat-eaters aged 20–79 were assessed using a validated food frequency questionnaire. Comparable GHG emissions parameters were developed for the underlying food codes using a dataset of GHG emissions for 94 food commodities in the UK, with a weighting for the global warming potential of each component gas. The average GHG emissions associated with a standard 2,000 kcal diet were estimated for all subjects. ANOVA was used to estimate average dietary GHG emissions by diet group adjusted for sex and age. The age-and-sex-adjusted mean (95 % confidence interval) GHG emissions in kilograms of carbon dioxide equivalents per day (kgCO₂e/day) were 7.19 (7.16, 7.22) for high meat-eaters ( > = 100 g/d), 5.63 (5.61, 5.65) for medium meat-eaters (50-99 g/d), 4.67 (4.65, 4.70) for low meat-eaters ( < 50 g/d), 3.91 (3.88, 3.94) for fish-eaters, 3.81 (3.79, 3.83) for vegetarians and 2.89 (2.83, 2.94) for vegans. In conclusion, dietary GHG emissions in self-selected meat-eaters are approximately twice as high as those in vegans. It is likely that reductions in meat consumption would lead to reductions in dietary GHG emissions.
18. 2016: Bryngelsson, David, et al. “How can the EU climate targets be met? A combined analysis of technological and demand-side changes in food and agriculture.” Food Policy 59 (2016): 152-164. To meet the 2 °C climate target, deep cuts in greenhouse gas (GHG) emissions will be required for carbon dioxide from fossil fuels but, most likely, also for methane and nitrous oxide from agriculture and other sources. However, relatively little is known about the GHG mitigation potential in agriculture, in particular with respect to the combined effects of technological advancements and dietary changes. Here, we estimate the extent to which changes in technology and demand can reduce Swedish food-related GHG emissions necessary for meeting EU climate targets. This analysis is based on a detailed representation of the food and agriculture system, using 30 different food items. We find that food-related methane and nitrous oxide emissions can be reduced enough to meet the EU 2050 climate targets. Technologically, agriculture can improve in productivity and through implementation of specific mitigation measures. Under optimistic assumptions, these developments could cut current food-related methane and nitrous oxide emissions by nearly 50%. However, also dietary changes will almost certainly be necessary. Large reductions, by 50% or more, in ruminant meat (beef and mutton) consumption are, most likely, unavoidable if the EU targets are to be met. In contrast, continued high per-capita consumption of pork and poultry meat or dairy products might be accommodated within the climate targets. High dairy consumption, however, is only compatible with the targets if there are substantial advances in technology. Reducing food waste plays a minor role for meeting the climate targets, lowering emissions only by an additional 1–3%. [FULL TEXT]
19. 2016: Springmann, Marco, et al. “Analysis and valuation of the health and climate change cobenefits of dietary change.” Proceedings of the National Academy of Sciences 113.15 (2016): 4146-4151. What we eat greatly influences our personal health and the environment we all share. Recent analyses have highlighted the likely dual health and environmental benefits of reducing the fraction of animal-sourced foods in our diets. Here, we couple for the first time, to our knowledge, a region-specific global health model based on dietary and weight-related risk factors with emissions accounting and economic valuation modules to quantify the linked health and environmental consequences of dietary changes. We find that the impacts of dietary changes toward less meat and more plant-based diets vary greatly among regions. The largest absolute environmental and health benefits result from diet shifts in developing countries whereas Western high-income and middle-income countries gain most in per capita terms. Transitioning toward more plant-based diets that are in line with standard dietary guidelines could reduce global mortality by 6–10% and food-related greenhouse gas emissions by 29–70% compared with a reference scenario in 2050. We find that the monetized value of the improvements in health would be comparable with, or exceed, the value of the environmental benefits although the exact valuation method used considerably affects the estimated amounts. Overall, we estimate the economic benefits of improving diets to be 1–31 trillion US dollars, which is equivalent to 0.4–13% of global gross domestic product (GDP) in 2050. However, significant changes in the global food system would be necessary for regional diets to match the dietary patterns studied here.  The food system is responsible for more than a quarter of all greenhouse gas emissions while unhealthy diets and high body weight are among the greatest contributors to premature mortality. Our study provides a comparative analysis of the health and climate change benefits of global dietary changes for all major world regions. We project that health and climate change benefits will both be greater the lower the fraction of animal-sourced foods in our diets. Three quarters of all benefits occur in developing countries although the per capita impacts of dietary change would be greatest in developed countries. The monetized value of health improvements could be comparable with, and possibly larger than, the environmental benefits of the avoided damages from climate change. [FULL TEXT]
20. 2018: Tweet thread by Frederic Leroy @fleroy1974 on Twitter : https://twitter.com/fleroy1974/status/1074111080052482053

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