Fig 1.
Historical annual global emissions from fossil CO2 use excluding carbonation (Fossil CO2) and from land use change (LUC CO2) (Gt CO2 per year) and global CH4 emissions from livestock (Mt CH4 per year).
Note that CO2 and CH4 results are expressed in different units and each refers to the left and right y axes, respectively. Data source: CO2: Friedlingstein et al. (2021) and CH4: Reisinger and Clark (2018) (1750–2009) and EDGAR database (2010–2019).
Fig 2.
Methane emissions from global cattle (aggregating dairy and beef cattle and buffalo) (a), dairy cattle (b), beef cattle (c) and buffalo (d) for both enteric and manure sources. Results are expressed as Mt CH4 per year. Data source: FAOSTAT.
Table 1.
Overview of the set-up of the different scenarios for testing the framework to estimate the impact of GHG emissions on global temperature change.
Fig 3.
Historical warming impact of global fossil CO2 emissions excluding carbonation (Fossil CO2), global land use change (LUC CO2) emissions and livestock CH4 as estimated by multiplying aggregated CO2 emissions and CO2-we (using GWP*) (for CH4 sources) emissions by the TCRE value: (a) 0.45°K/Tg CO2 and (b) 0.40°K/Tg CO2. For livestock, there are 3 different assumptions of CH4 emission rates from global livestock in the period between 1750–1860: # and solid orange line: 0 CH4/yr emissions, $ and yellow line: Sustained increased emissions from 11.5 to 22.3 kt CH4/yr and & and dotted orange line: 22.3 kt CH4/yr during 1750–1860.
Table 2.
Additional temperature from fossil CO2 emissions excluding carbonation, land use change (LUC) CO2 and livestock CH4 for different periods (1770–1970; 1970–1990; 1990–2019) and % of this temperature within each period that can be attributed to each sector.
Fig 4.
Additional warming associated with methane emissions from different sources (enteric and manure) of global cattle systems (dairy, beef and buffalo) until 2019 and since 1981(a) and 1990 (b). Additional warming is calculated by multiplying cumulative CO2-we (using GWP*) emissions with the TCRE value (0.45°K/Tg CO2-we).
Fig 5.
Averaged annual additional warming (as calculated by dividing the additional warming within the analysed period by the number of years in such period) associated with global fossil fuel CO2, land use change CO2 and global cattle CH4 for periods with different reference years (1981, 1990, 2000, 2005 and 2010) until 2019.
Fig 6.
Cumulative emissions (a) and average annual emissions (as calculated by dividing the cumulative emissions within the analysed period by the number of years in such period) (b) as expressed using GWP* (CO2-we) and conventional GWP100 (CO2-e) coming from methane emissions from global cattle systems for different reference years (1981, 1990, 2000, 2005 and 2010) until 2019. (white: CO2-we and grey: CO2-e). Note that axes from Fig 6A and 6B have different magnitudes.
Fig 7.
Warming impact of global fossil CO2 emissions (a), global land use change (LUC) emissions (b) and livestock CH4 (c) as estimated by multiplying aggregated CO2 emissions and CO2-we (using GWP* for CH4) emissions by the TCRE value (0.45°K/Tg CO2) since 1770 and considering 3 different future pathways of emissions (2020–2100) (unchanged, reducing 1% per annum, constant over time and reducing emissions gradually until reaching 0 emissions (net-0 CO2 or CO2-e using GWP100 for livestock CH4) in 2100: Reducing fossil CO2: 0.44 Gt CO2/yr; LUC CO2: 0.04 Gt CO2/yr and livestock CH4: 1.5 Mt CH4/yr). Note that axes for global fossil CO2 is x5 times larger than that for LUC CO2 and livestock CH4.
Fig 8.
Historical (1990–2019: solid line) and future (2020–2050: dotted line) pathways for global cattle CH4 emissions leading to an stabilisation or no additional warming of their impact on global temperature (both historical and future expressed as CH4: green line or CO2-we using GWP*: orange line) (a) and its corresponding impact on additional temperature caused (blue line, historical: solid line, future: dotted line) as estimated by multiplying aggregated CO2-we (using GWP*) emissions by the TCRE value (0.45°K/Tg CO2) (b).
Fig 9.
Historical (1990–2019: solid line) and 3 future (2020–2050: dotted line) reduction pathways for global cattle CH4 emissions, all leading to a stabilisation of their impact on global temperature (a). These emissions are expressed as CO2-we (warming-eq emissions) using GWP* (b) and its corresponding impact on additional temperature caused is estimated by multiplying aggregated CO2-we (using GWP*) emissions by the TCRE value (0.45°K/Tg CO2) (c). The three future pathways correspond to a ‘fast’ first CH4 reductions (dotted green line), ‘sustained’ reductions at 0.32% decrease per year (constant over time) (dotted orange line) and ‘delayed’ introduction of CH4 reductions (dotted black line).