Climate impacts of fossil fuels in today’s electricity systems

Oil, coal, and gas account for approximately 80% of global primary energy, but only a portion of total airborne CO 2eq (approx. 35% at GWP 20 to 65% at GWP 100 ), even though they account for 95% of total measured CO 2 emissions. The benefits of these energy sources, as well as their related costs, are not all incorporated in current energy policy discussions. Global greenhouse gas policies must include documented changes in measured airborne CO 2eq to avoid spending large amounts of public funds on ineffective or sub-optimal policies. The authors examined airborne CO 2 , which is less than half of emitted CO 2 , as well as reported CH 4 emissions and the global warming potential of CH 4 as published by the IPCC for coal and natural gas. The surprising conclusion is that surfaced-mined coal appears ‘better for the climate’ than the average natural gas, and all coal appears beneficial over LNG. Therefore, current CO 2 -only reduction policies and CO 2 taxes are leading to unintended consequences and the switch from coal to natural gas, especially LNG, will not have the desired impact of reducing predicted future global warming; in fact, quite the contrary. A large portion of anthropogenic global warming is attributed by the IPCC and IEA to CH 4 , but it must be noted that CH 4 emissions from natural sources and from agriculture account for approximately 40% and 25% of annual global CH 4 emissions respectively. Energy accounts for about 20% of documented CH 4 emissions. CO 2 contributes only approximately 35% of annual airborne anthropogenic GHG emissions after accounting for CH 4 , over a 20-year horizon. At a 100-year horizon, the contribution of CO 2 increases to approximately 60%. Energy policies that do not consider all GHG emissions along the entire value chain will lead to undesired economic and environmental distortions. All carbon taxation and CO 2 pricing schemes are incorrect and need to be revised. At IPCC’s GWP 20 an approximately 2% 1 higher loss of CH 4 across the value chain prior to combustion of natural gas versus coal will lead to ‘climate parity’ of coal with natural gas. According to public data, natural gas value chains have high CH 4 and undocumented CO 2 losses. On a global average, using only IEA-documented CH 4 data, natural gas emits approximately 15% more CO 2eq than surface-mined coal, over a 20-year horizon. This difference will increase as the use of shale gas and LNG expands. Investors should support all energy systems in a manner that avoids an energy crisis, including intermittent renewable energy systems where they make sense. If CO 2 emissions need to be reduced, one of the most effective ways would be to install ultra-supercritical power plants with CCUS technology. However, the undisputed benefits of increased CO 2 concentrations in the atmosphere because of its promotion of photosynthesis and plant growth effects (fertilization) need to be considered in energy policy decisions as well. The authors suggest that future research and development should concentrate on reducing net emissions from fossil fuel power plants and providing cost-effective and reliable new conventional power generation capacity, utilizing clean coal and clean natural gas technology.


Introduction
In 2019, fossil fuels -in order of importance oil, coal, and gas -made up approximately 80% of global primary energy (PE) production totalling approximately 170 000 TWh or 600 EJ. Despite the covid pandemic and significant wind and solar capacity additions, the percentage did not change much in 2021. This proportion has also been largely constant since the 1970s, when energy consumption was less than half what it is today. The same three fossil fuels made up over 60% of global gross electricity production, totalling approximately 27,000 TWh in 2020 2 . It is important to note that global electricity production makes up about 40% of PE, with transportation, heating, and industry accounting for the remaining approximately 60% (see also Figure 1).
Renewables in the form of wind and solar -while not the subject of this paper -accounted for approximately 3% of global PE and 8% of global gross electricity production in 2019, and this was largely unchanged in 2020 and 2021 (refer to , for more details on solar energy). For comparison, coal and gas combined accounted for approximately 50% of global PE and 60% of global gross electricity production.
The UN projects that global population will rise from the current 8 billion to 10 billion in the next 30 years (Roser, Ritchie, and Ortiz-Ospina, 2013), and may peak around 11-12 billion by the end of the century. Despite continued improvements in energy efficiencies, rising living standards in developing nations are forecast to increase global average annual per capita energy consumption from 21,000 kWh to 25 000 kWh by 2050 BP, 2020). As a result, global PE consumption could rise by as much as 40% to 60% by 2050 (a 25% population increase and a 20% PE/capita increase translates to 50% PE demand increase). Energy demand growth is fuelled by developing nations in Asia, Africa, and South America. Developed nations are expected to consume less energy in the decades to come, owing to population stagnation or decrease, and increases in energy efficiency.
However, it should be noted that recent models by McKinsey (McKinsey Energy Insights, 2019 estimate that global PE demand will only increase by 14% by 2050, while the International Energy Agency's (IEA's) 2021 Net-Zero Pathway (IEA, 2021) models a reduction by approximately 10% by 2030 to reach 'net zero' CO 2 emissions (not CH 4 emissions) by 2050, although this is questioned by the authors. The same reports estimate that global power generation will almost double from 2020 to 2050 (McKinsey Energy Insights. 2019), also driven by the projected electrification of transportation. The Institute for Energy Economics in Japan (IEEJ) predicts global PE demand to increase by 30% by 2050, while the American Energy Information Agency (EIA) predicts a 50% increase (IEEJ, 2019;EOA, 1019EOA, , 2021 in line with the authors' analysis. It is prudent to assume that wind and solar alone will not be able to generate enough energy to match the expected demand increase to 2050. This is confirmed by the IEEJ's October 2020 report (IEEJ, 2019;EIA. 2019 forecasting an absolute increase in fossil fuels' share in PE in its reference case by 2050. In July 2021, the IEA (2021) confirmed that '…[renewables] are expected to be able to serve only around half of the projected growth in global [electricity] demand in 2021 and 2022'. Over 60% of global electricity growth during 2021 was fuelled by coal and natural gas (NG), and only 30% from renewables. For PE growth, the renewable share will be only a fraction, about 20%, as about 2/5th of PE is for electricity. Schernikau, Smith, and Falcon (2022) provide more details on the global energy landscape, including a discussion on the pros and cons of using PE with increased penetration of renewable energy.
Even if wind and solar were to fulfill all future increases in PE demand, it becomes clear that for the next 30 years and beyond we will continue to depend on conventional energy resources for a large portion, if not the vast majority, of our global energy needs. Therefore, given the relevance of coal and natural gas to the future energy scene, this paper examines the global warming impact of such fossil fuels.

Which fossil fuel is 'best for the climate'?
Coal and natural gas are the main fuels for electricity generation, while oil is the main fuel for transportation. Nuclear's share reaches about 10-11% for electricity and 5-6% for PE (see Figures  1 and 2). Nuclear energy is not discussed further in this paper despite its many benefits and challenges. Given the importance of coal and NG, especially for electricity but also for energy as a whole (approx. 60% of electricity and 50% of PE), the authors review the impact of both coal and NG on global warming, relying on reported data by the IPCC, the IEA, and Our World in Data.

Introducing greenhouse gases and global warming potential
It is undisputed that (1) the average global temperature has increased since the 1800s -the end of the Little Ice Age, and that (2) humans have contributed to global warming in the past and will continue to do so. It is also undisputed that (3) CO 2 is a greenhouse gas (GHG) and that increasing airborne CO 2 levels contribute to global temperature change, in concert with other climate forcings.   In addition, it is undisputed -though less well knownthat the global warming impact of CO 2 or any GHG declines logarithmically, thus each additional ton of CO 2 airborne has less capacity to increase temperatures (Wijngaarden and Happer, 2020). CO 2 is active in the wavelength band from about 12-18 μm, which has been essentially saturated. This works in such a way that additional CO 2 molecules can only slightly widen the wavelength band in which the molecule can impact outgoing thermal radiation. In the absence of GHGs, the Earth's surface temperature would be on average about -18°C; but with GHGs the surface reaches a temperate and livable 15°C. The 33K difference is ascribed to the so-called 'greenhouse effect' of the atmosphere (World Meteorological Organization, 2021).
The IPCC in its 5th Assessment Report AR5 gives the global warming potential (GWP) of several of GHGs over both a 20and a 100-year horizon. These GWPs are little changed in AR6, published in August 2021. The IPCC (2014a) defines GWP as 'An index measuring the radiative forcing following an emission of a unit mass of a given substance, accumulated over a chosen time horizon, relative to that of the reference substance, carbon dioxide (CO 2 )'. There remains scientific uncertainty and debate about the global warming potential, but for the sake of this paper the authors choose to use the official reported IPCC data 3 (Cain, 2018;Derwent, 2020;ClimateAnalytics. 2017;Lynch et al., 2020). For instance, the IPCC notes the large uncertainties in the GWP of CH 4 -between about 32% and 40% (see IPCC, 2021, Table 7.SM8) The definition of GWP is given in many sources, but explained well by . Equation [1] shows that the GWP of a particular molecule j is the ratio to CO 2 , denoted by i in the equation, integrated over time following an initial pulse of gas at t = 0. This metric implies that a gas which decays quickly will have a greater initial GWP than a gas which decays more slowly. Kleinberg's academic paper places the GWP in the correct physics perspective while pointing out its shortcomings. [1] Considering the urgency of addressing global warming as well as the declared climate crisis by the UN, governments, and institutions, the authors use the IPCC's 20-year GWP 20 metric for CH 4 of 84× and illustrate the implication on energy policy if one were to accept the IPCC's GWP. For comparison, IPCC's 100-year GWP 100 metric for CH 4 is 28×. The reader can adjust from GWP 20 to GWP 100 by dividing or multiplying any relevant CH 4 number by 3 = 84 / 28. The GWP index is not radiative forcing but is a 'metric' intended to indicate how much 'worse' or 'better' a greenhouse gas is compared to CO 2 (GWP of 1) and its impact on global warming (IPCC. 2014). The following six main GHGs and their respective GWPs are mentioned by the IPCC (2014b, 2014c): ➤ Water vapour (H2O): The most important and most abundant GHG, but not further detailed by the IPCC. The authors are concerned that the greenhouse effect of water is not included in the IPCC analysis, apparently due to its complicated variability and energy transport effects.

The misconception of reported global CO 2 emissions and error in carbon taxing
A recent survey identified over 1,200 different climate laws and policies (Grant et al., 2020). The vast majority of reports on global CO 2 emissions as well as most proposed climate policies, laws, and regulations, and global carbon-tax discussions centre on measured-human-energy CO 2 emissions. This is despite recent efforts by the IEA and other institutions to understand other GHGs better, primarily the shorter-lived GHG CH 4 . The National Oceanic and Atmospheric Administration (Tans, 2021;Dlugokencky, 2021) notes that atmospheric concentrations of CH 4 increased from about 1630 ppb (parts per billion mole-fraction CH 4 ) in 1984 to 1880 ppb in 2021, an increase of 15% or 0,4% per annum. During the same time, the atmospheric concentration of CO 2 increased from approximately 345 ppm to 415 ppm, a 20% or 0.5% annual increase (Tans, 2021;Dlugokencky, 2021). The IEA found that in June 2021, 73% of the world's countries had announced net-zero pledges for CO 2 , but only 28% had policies to reduce CH 4 , with no zero-CH 4 pledge. Governmental discussions on the 'social cost of carbon' (SCC) or any CO 2 tax have led to significantly distorted policies as they entirely ignore natural CO 2 uptake and other GHG emissions. GHG emission measurements should at least include CO 2 eq emissions from all sources, including but not limited to CH 4 emissions from livestock agriculture, energy production, or natural causes (see Table I). GHG emissions from changes in land use, nitrous oxides (N 2 O), or fluorinated gases (F-gases), which together may add another 5-10% of total anthropogenic GHGs (Olivier and Peters, 2020), are not discussed in this paper.
The omission to include at least CH 4 emissions may be driven primarily by the simplicity of measuring or easily calculating human-energy CO 2 emissions. The chemistry and physics are simple for CO 2 , assuming a certain efficiency of a given power plant as well as measuring the tons of fossil fuel combusted. From this data, one can relatively easily estimate CO 2 emissions from such a plant. For instance, 1 t of carbon equals 3,67 t of CO 2 , purely based on the molecular mass. Thus, the complete combustion of coal with a 50% carbon content (as-received basis) will simply result in 50% of 3,67 t, or 1,8 t, of CO 2 per ton of coal burnt. These CO 2 emissions are detailed by country, by application, by fuel source, by income, even by activity type, and in many other ways in quite an elaborate process at a global scale. For example, recently, credit cards have become available that can manage and limit your spending based on the 'CO 2 footprint' of your purchases'.
One misguided result of limiting efforts on measured-humanenergy CO 2 emissions is the widely accepted government policy of switching from coal to NG (in most cases to LNG) to slow or MARCH 2022

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The Journal of the Southern African Institute of Mining and Metallurgy limit global warming. Consequently, many international banks, institutions, and conglomerates, e.g., the Tesla gas-fired power plant in its new Berlin Gigafactory (Randall, 2020) or the EU's plan to label natural gas as green (Abnett and Jessop, 2022), are withdrawing from coal but are actively supporting NG as a 'bridge fuel'. Another recent example, the world's leading coalto-liquids company Sasol in South Africa was applauded for its announcement in August 2021 to develop NG. Global LNG export terminal capacity is also expected to more than double from 440 Mt in 2020 to over 1,000 Mt in 2030.
Most scientific studies, government reports, or any carbon tax for that matter, consider solely CO 2 emissions from combustion when recommending NG or LNG as a bridge fuel towards a netzero future (see Figure 4). This is indisputably wrong and leads to distorted policies, as will be explained in the following pages. A wider selection of additional studies, reports, and press releases on CH 4 emissions is given in the Appendix.

Reported CO 2 and CH 4 emissions
For the purpose of this paper, the authors rely on reported CO 2 and CH 4 emissions from the IEA and Our World in Data, which in turn rely on the Global Carbon Project, the Carbon Dioxide Information Analysis Centre (CDIAC), and Saunois et al. (2020). The IEA notes, however, that estimates of CH 4 emissions are subject to a high degree of uncertainty. Top-down estimates used by the IEA are lower than bottom-up estimates, and estimates have been increasing steadily. The IEA's reported CH 4 emissions data is summarized in Table I. In addition, the authors rely on the IPCC's confirmation that about half of the CO 2 emitted to the atmosphere disappears annually into global ecological and physical sinks, i.e., taken up by plants through photosynthesis, fertilization, and by oceans. In fact, IPCC AR6 (IPCC, 2021) states with high confidence that 54% of CO 2 is removed and 46% remains airborne in the atmosphere. During the period 2010-2019, 31% of the emitted CO 2 was taken up by ecosystems (e.g., plants) and 23% by the oceans.
Several other studies (e.g. Knorr, 2009) also confirm that less than half of CO 2 emissions remain airborne. Logically, only airborne CO 2 can contribute to the greenhouse effect. This 'natural CO 2 uptake' is highly relevant when comparing CO 2 to other GHG emissions that do not contribute to plant growth.
Thus, governments and institutions should switch from 'measured-human-energy CO 2 emissions' toward the more correct metric that the authors call 'changes in airborne CO 2 eq '. Figure 2 and the following section illustrate this process.
Documented CO 2 and CH 4 emissions are detailed in Table I and Figure 3. Because IPCC's 20-year global warming potential (GWP 20 ) for CH 4 is 84 times higher than that for CO 2 , the calculations are straightforward and as follows Roser, 2020a, 2020b): from natural sources. ➤ As a result, global changes in airborne CO 2 eq from anthropogenic sources of CO 2 and CH 4 at GWP 20 are approximately 47 Gt (17 Gt from CO 2 and 30 Gt from CH 4 ). Fossil fuels accounted for approximately 60% of total anthropogenic CO 2 eq . Coal itself contributed just over 20%, oil just below 20% and NG 15%. For comparison, at GWP 100 fossil fuels accounted for approximately 75% of total anthropogenic CO 2 eq . ➤ Total measured-human-energy airborne CO 2 accounted for approximately 35% of the total changes in airborne anthropogenic CO 2 eq from both CH 4 and CO 2 at GWP 20 . When considering CH 4 's 100-year global warming potential GWP 100 this increases to 65%.

Air pollution from coal versus gas
Coal production, transportation, and combustion adversely affect the environment in many ways, including but not limited to particulate emissions and air pollutant emissions. However, air pollution from combustion of coal is reduced to a bare minimum in modern coal-fired power plants utilizing clean coal technology where the newest filter and waste product management systems are employed. For example, the United Arab Emirates commissioned one of the world's most advanced and newest 2,4 GW ultra-supercritical (USC) coal-fired power plants in 2021  The 10-15% concentrated CO 2 stream from coal plants could, in principle and if required, be captured and utilized, or stored . Carbon capture utilization and storage (CCUS) at fossil power plants would be more effective than any direct air capture (DAC) from the 0,04% CO 2 content of the atmosphere or reducing CO 2 through other means. Qvist et al. (2020) present a case study for Poland.
Coal mine methane (CMM) leakages are associated primarily with underground coal mining. This is the CH 4 which is released during exploitation of coal seams and is vented to the atmosphere. Coalbed methane (CBM) can be extracted for commercial utilization from unmined coal seams. This extraction is usually done either by drilling vertically into the seam (SIS methane drainage) or drilling directionally along the seam (UIS methane drainage) (Zheng et al., 2019). CBM projects that utilize the CH 4 are supported under the Kyoto Protocol and investors can claim CO 2 credits, either using them to offset their own emissions or by selling them on the open market.
Underground coal mines, once production is halted and the mine is abandoned, may continue to leak CH 4 . This leakage is referred to as abandoned mine methane (AMM) (Kholod et al., 2020). CH 4 migrates into the abandoned mine from connected coal deposits. If not prevented by an adequate sealing, the liberated gas will migrate to the surface and escape to the atmosphere through natural and mining-related fractures and other conduits. On average, the CH 4 content per ton of coal mined increases with increasing depth.
It is important to note that surface coal mines rarely emit CH 4 . Even if the coal seams had collected, emitted, or stored CH 4 during burial, when the pressure is reduced or at shallower depths, the gas escapes. As a result, CH 4 from coal seams closer to the surface was vented over the past millions of years. Hence, irrespective of coal quality, coal seams closer to surface and mined by opencast methods will not normally emit CH 4 (Lloyd and Cook, 2005;Cook, 2013).
Much effort and investment are required to further reduce the negative environmental impact of coal production, processing, transportation, and combustion; although the technology mostly exists today. Generally, the combustion of coal causes more air pollution than NG, due to the emission of particulate matter, SO x , and NO x . Coal ash may be useful for certain industrial processes such as cement manufacturing, but is often of significant environmental liability. Also, the production and transportation of coal usually effects the environment more than NG does (other than CH 4 ). Any unutilized leaked or 'fugitive' CH 4 from coal mining can be considered a component of air pollution and contributes to the GWP of CH 4 .
Pollution from natural gas other than CH 4 also includes SO x and NO x . Unconventional gas production generally affects the environment more than conventional gas, e.g., from chemicals used during fracking and/or drilling. Furthermore, it is understood that CH 4 does not only have climate impacts but also affects air quality because it is an ingredient in the formation of groundlevel ozone, a dangerous air pollutant that can cause respiratory and cardiovascular diseases. Other toxic gases and hazardous air pollutants are also emitted along with CH 4 ; these can lead to long-term health effects or even death (CATF, 2021). CO 2 , on the other hand, does not affect human health unless average ambient concentrations continuously reach levels 10 to 100 times higher than current atmospheric concentrations of about 420 ppm, at which may then cause drowsiness, tiredness, and headaches. Humans exhale about 40 000 ppm (4%) of CO 2 . CO 2 concentrations in buildings vary from 400 to 2 000 ppm (author's own measurements).

Surface-mined coal versus natural gas
With the introduction of a new metric, anthropogenic 'changes in airborne CO 2 eq ' using IPCC's GWP metric and IEA data, it is necessary to summarize and re-assess discussions on energy policy. Both coal and NG have benefits and issues. When choosing coal versus NG, all economic and environmental benefits and problems should be compared appropriately based on available data. NG is an important and favourable energy resource and is much needed for a stable and affordable energy system, as are coal, nuclear, hydro, and other resources.
Applying changes in airborne CO 2 eq , the authors calculated the following GHG impacts, with and without CH 4 emissions, using the IPCC's GWP 20 and IEA primary energy data (see Tables I and  II): ➤ Pure combustion with zero energy-related fugitive CH 4 emissions: 0,09 Mt CO 2 per TWh for NG versus 0,15 Mt CO 2 per TWh for coal. NG emits about 40% less CO 2 than coal. This is the typical global ratio. ➤ With fugitive energy-related CH 4 emissions: 0,18 Mt CO 2 eq per TWh for NG versus 0,23 Mt CO 2 eq per TWh for coal. NG emits about 20% less CO 2 eq than coal. This is the actual global ratio based on known data. ➤ NG versus surface-mined coal: 0,18 Mt CO 2 eq per TWh for NG versus 0,15 Mt CO 2 eq per TWh for surface-mined coal. NG emits about 15% more CO 2 eq than surface-mined coal. Based on the calculations above and the fact that surface coal mines rarely emit CH 4 , it can be demonstrated that at GWP 20 , on a global average, surface-mined coal emits about 15% less CO 2 eq than NG. This figure increases as the use of shale gas and LNG expands. For completeness, at a 100-year horizon, at GWP 100 surface-mined coal still emits about 25% more CO 2 eq than average NG when comparing primary energy supply. However, for LNG the situation does not look as favourable even at GWP 100 where coal is on par with NG at approximately 5% additional CH 4 loss prior to LNG combustion (see Table I and calculations in Ritchie and Roser, 2020a). It must be noted that if one were to use electricity production, rather than primary energy, as the basis for comparison, the ratios further improve in favour of coal since gas causes higher CH 4 emissions for less electricity produced. However, it is difficult to detail the non-electricity energy contributions of gas and coal, and therefore the authors chose to use PE only, which is also more conservative and relevant to this analysis.
In addition to CH 4 , CO 2 is also emitted during NG (and especially LNG) production and processing. These CO 2 emissions are currently not considered in the life-cycle analysis of the gas chain; neither are they included in the reported global CO 2 emission data nor in the analysis herein. The Institute for Energy Economics and Financial Analysis (IEEFA, 2020) presented a detailed analysis of the Australian LNG industry and associated CO 2 emissions with the subtitle 'Increased Emissions The Journal of the Southern African Institute of Mining and Metallurgy VOLUME 122 MARCH 2022

[from LNG] Have Offset Any Gains From Renewables' Rise in
Electricity Generation'. The IEFFA reports that new Australian LNG projects emit on average 0,7 t CO 2 per ton LNG during production only. For example, according to the report, the Darwin LNG Barossa field may even emit 2,4 to 3,6 t CO 2 per ton LNG, thus 'the total project could become a CO 2 venting factory with an LNG by-product'. Another documented example is the CO 2 emissions of the Western Australian Gorgon LNG project. The Conservation Council of Western Australia (2019) documented in 2019 that Western Australian LNG operations emit on average approximately 0,6t CO 2 per ton LNG produced. The CO 2 streams stem from the raw feed gas extracted from the oceans that is vented to the atmosphere. This stream of CO 2 was planned to be captured but this was not fully implemented by 2021 (Milne, 2019;Morton, 2021) (see also Figure 4). We reiterate, the analysed CO 2 eq figures in this paper do not consider any CO 2 emissions associated with LNG production, processing, or transportation and thus underestimate the total CO 2 eq emissions of natural gas.

Total global natural gas versus coal
It is important to keep in mind that fugitive CH 4 must include all CH 4 sources and not only those from energy. Sources of CH 4 must include agriculture, wetlands, waste disposal, thawing permafrost, and others as documented by the IEA (see Figure 3). Natural CH 4 emissions amount to about 40%, and agriculture to about 25%, of total annual fugitive CH 4 (see Table I). The GWP then dictates the global warming potential of CH 4 from all sources other than from energy. These non-energy CH 4 emissions dominate CO 2 eq emissions from all coal. The competition is not even a close race, and little can be done to alter this ratio since wetlands and agricultural sources are inviolate in the global ecology and in the sustenance of human populations. Ocko et al. (2021) conclude that CH 4 accounts for 'at least a quarter of today's gross warming' and also detail estimates of natural CH 4 sinks. The IEA (2021) stated in 2021 that 'Methane has contributed around 30% of the global rise in temperature today'. In addition, using the GWP 20 metric it can now be demonstrated that marginally, NG emits more CO 2 eq than the average coal as soon as more than about 2% 1 of CH 4 is lost prior to gas combustion compared to coal along the value chain of production, processing, and transportation of pipeline natural gas (PNG) or LNG. For comparison, using GWP 100 coal reaches climate parity with NG at about 5% additional CH 4 loss prior combustion 4 . This figure is principally confirmed by Ladage et al. (2021), who estimate a break-even CH 4 leakage rate of 2,7% for the USA and 4,1% for Germany. However, Ladage et al. do not consider the natural CO 2 uptake as confirmed by the IPCC, and thus overestimate the break-even CH 4 leakage rate by about 50%. The exact relationship of natural gas or LNG to coal depends on the origin of the gas, the distance and efficiency of the gas logistics, as well as the technology used for refining, liquefaction, transportation, and regasification (Figure 4 and Appendix). It is relatively certain and the authors' understanding, though unproven due to lack of data, that the global LNG supply chain on average results in CH 4 leakages greater than 5% (see Appendix).

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The Journal of the Southern African Institute of Mining and Metallurgy only. Based on annual global CH 4 emissions of approximately 590 Mt and total anthropogenic emissions of about 360 Mt, anthropogenic CO 2 eq emissions from CH 4 are about four times higher than CO 2 emissions from coal alone, at GWP 20 (see Table I). LNG and shale gas production, processing, and/or transportation increase fugitive CH 4 emissions per unit of energy produced and make the situation even less favourable for gas.
This conclusion is a surprise and one that was not anticipated by the authors. When we factored in the GWP 20 value from the IPCC AR5 and AR6 reports, the GWP for CH 4 -from all sources -dominates the equation. CH 4 , until combusted, is a far more potent greenhouse gas (for caluclations see footnote 4 on page 139) than CO 2 , and it lacks the beneficial role of CO 2 in photosynthesis which compensates at least part of other possible effects of CO 2 on the climate.
As discussed earlier, both CO 2 and CH 4 are GHGs that contribute to global warming. For this reason, both the costs and the benefits of CO 2 and CH 4 should be considered in any cost and benefit analysis of each hydrocarbon (coal, natural gas, and oil) compared to renewable sources of power. Readers are invited to consider the general practice in Western Europe to couple intermittent wind or solar with natural gas (see new gas firedpower plants in Germany or the EU's plan to put gas on the 'green' list (Abnett and Jessop, 2022;Independent, 2021).
Disregarding any benefits from CO 2 , Nobel Prize winner Professor William Nordhaus (2018) calculated a GDP cost of 2,8% in 2100 from global warming, assuming his optimal scenario with 4,1°C warming. For comparison, the UN announced (UNFCC, 2021) that their current climate trajectory is in line with about 2,7°C warming from pre-industrial times (1850-1900) until the end of century, of which 1,1°C to 1,2°C has already occurred.
Based on his work, Nordhaus earned the Nobel Prize for 'Climate Economics' in 2018. He estimates the GDP cost of global warming under different scenarios using his DICE model (the merits of using the GDP metric will not be elaborated in this paper). Suffice to say that Nordhaus makes the following important statements confirming that reduced use of fossil fuels will lead to reduced growth and therefore wealth: ➤ '… the revised DICE model shows more rapid growth of output in the baseline or "no-[climate]-policy" path compared to earlier DICE versions and most other models.
➤ '… the international target for climate change with a limit of 2°C appears to be infeasible with reasonably accessible technologies even with very ambitious abatement strategies. This is so because of the inertia of the climate system, of rapid projected economic growth in the near term, and of revisions in several elements of the model. ➤ 'A target of 2,5°C is technically feasible but would require extreme and virtually universal global policy measures in the near future.' Professor Nordhaus' optimal DICE scenario corresponds to a peak in CO 2 emissions (not airborne CO 2 eq ) around 2050 at approximately 40 Gt and a global warming of 4,1°C using the implausible IPCC RCP8,5 climate scenario. For comparison, it is predicted that covid-19 will cause up to a 10% drop in GDP by 2050; in line with the 10% drop in GDP after 3 years during the Great Depression (IEEJ , 2020). Lomborg (2020) and Kahn et al. (2021) principally confirm Nordhaus' calculations.
The potential effects of climate changes may be considerable and should not be discounted. However, the benefits of increased CO 2 concentrations in the atmosphere because of their undisputed fertilization effects on plants are confirmed by numerous peer-reviewed studies, a selection of which is listed by Idso (2021). In addition to adjusting for CO 2 fertilization, the modelled economic impact of global warming -to be fair and complete -should be compared to the costs and impacts of prematurely forcing energy systems away from conventional fuels prior to having a truly sustainable energy solution.
Carbon, oxygen, hydrogen, and nitrogen are the four most important elements for life. CO 2 is a key building block for all life on Earth as all plant life depends on CO 2 , water, and solar radiation for photosynthesis. In fact, atmospheric CO 2 is the sole source of carbon contained in plants, and therefore in human and animal bodies.
The CO 2 concentration in the atmosphere increased by a little more than 0,01% or 100 ppm (by over 30%) in the past 100 years, apparently due mainly to combustion of carbon-rich oil, coal, and NG. The release of this additional CO 2 has contributed to warming and to noticeable greening of our planet. NASA and the World Economic Forum confirm that elevated CO 2 , slight warming, and precipitation increases contribute to the overall net greening of the Earth over the past decades (NASA Earth Observatory. 2019, Dunne, 2019). The increase in the Leaf Area Index (LIA) and Vegetation Index due to CO 2 fertilization has been confirmed by several researchers, e.g., Zaichun et al. (2016) and Wang et al. (2020). This greening is crucial in providing sufficient food to the growing population and its benefits have not been properly calculated. Zhu et al. (2016) point out that vegetation increased by about 14% from 1981 to 2014, about 70% of which is due to CO 2 fertilization. The growth equals an area twice as large as the USA. Deforestation counteracts CO 2 fertilization and needs to be further reduced; however, at a global scale, more biomass is added than is lost by deforestation.
Atmospheric CH 4 , in contrast, has no benefit to the environment but only costs. CH 4 needs to be captured to have value for energy generation. CH 4 that ends up in the atmosphere, according to the IPCC, is a far more potent GHG causing global warming (see footnote 4 , p.139). Additionally, it is understood that CH 4 does not only have climate impacts but also affects air quality because it is an ingredient in the formation of ground-level ozone, a dangerous air pollutant.
In summary, higher CO 2 emissions such as those from fossil fuel combustion are more beneficial for plant life relative to lower CO 2 emissions (the emphasis is on plant life). Higher CH 4 emissions have no benefit to the environment, are a potential health hazard, and have a larger GHG effect. These undisputed facts also need to be considered in energy policy.

Conclusions
This paper has sought to raise awareness that oil, coal, and natural gas account for approximately 80% of global PE and 95% of measured-human-energy CO 2 emissions, but a smaller portion of total anthropogenic airborne CO 2 eq (about 55% at GWP 20 to 70% at GWP 100 ). The benefits of these energy sources as well as their related costs are not all incorporated in current energy policy discussions. Anthropogenic CO 2 emissions account only for about 35% of total anthropogenic airborne CO 2 eq at GWP 20 (60% at GWP 100 ) after accounting for CH 4 .
It is evident that global GHG policies at least need to include documented changes in anthropogenic measured airborne CO 2 eq to avoid spending large amounts of public funds on ineffective or sub-optimal policies. Nowadays many governments, most global funds, international banks, conglomerates, and insurers have publicly announced they will abandon coal but will continue to support LNG and PNG projects, which are required to power human life.
The authors recommend that energy policies be reviewed taking all available information into account. Policies that focus only on combustion but leave out the true and full life-cycle emissions of all types from mining, processing, transportation, and utilization will lead to environmental surprises and potentially very large economic costs. The authors strongly support the fact that energy from all sources, including natural gas, oil, coal, nuclear, and renewables, is required to eradicate poverty. Increased wealth translates to increased resilience against illness and natural disasters.
Applying the IPCC's 20-year global warming potential GWP 20 , measured CH 4 emissions significantly outstrip global anthropogenic airborne energy-related CO 2 , or coal's total CO 2 eq emissions (see Tables I and II). Moreover, the dominant CH 4 emissions are not from human energy-related sources, which contribute only about 20%, but they arise from natural wetlands, agriculture, and waste handling. Elimination of those CH 4 sources would mean eliminating biologically productive areas, food resources, and the waste products of billions of people (Figure 3).
Using UN-funded IPCC and IEA data sources, it can be calculated that at GWP 20 , on a global average, surface-mined coal emits about 15% less CO 2 eq than natural gas. This figure increases as the use of shale gas and LNG expands. At a 100-year horizon (GWP 100 ) surface-mined coal still emits 25% more CO 2 eq than average NG. However, for LNG the situation does not look as favourable, even at GWP 100 where coal is on a par with NG at 5% additional CH 4 loss prior to combustion. Additional CO 2 releases from NG or LNG production are not measured nor accounted for. These observations make the case that investors should not favour NG over coal for electricity production but should support all energy systems in a manner that avoids an energy crisis, including variable renewable energy systems where they make sense. If CO 2 emissions need to be reduced, one of the most effective ways would be to install CCUS technology  However, the benefits of CO 2 through fertilization need to be fairly considered and evaluated.
The authors suggest that future research and development should concentrate on reducing net emissions of fossil fuel power plants and providing cost-effective and reliable conventional new power generation projects. This should be dedicated to ultra-supercritical (USC) power plants for increased efficiency, whether fossil fuel-fired or biomass-fired. The introduction of USC technologies is already growing in China and other countries and should be introduced -possibly at no cost to accelerate their deployment -to all developing countries, such as Bangladesh, Pakistan, Vietnam, Indonesia, South Africa, Kenya, Nigeria, and countries in South America. China, instead of forswearing support for coal-fired plants outside its borders, could then justify support for construction of efficient USC plants worldwide. Such advanced high-efficiency and low-emission (HELE) plants could replace less efficient existing power plants or even provide new facilities, all of which would support increasing economic activity, reduce emissions, and improve the quality of life for the growing population.
USC technology would have an immediate positive effect on nature  at a lower cost than installing grid-scale intermittent renewable energy systems with the required backup or storage. Fossil fuels, including natural gas and coal, require investment, not divestment, in the interest of our planet's health and to eradicate (energy) poverty.

Acknowledgement
The authors declare that they did not receive any financial or other support from any company or organization for this paper. A number of international studies and press releases, mostly funded by environmental organizations and even the gas industry itself, confirm that for 'the climate', LNG and shale gas are at best on a par with coal or will emit higher relevant GHG emissions.

Key abbreviations
In the past few years there has been a shift to more focus on methane, as illustrated by IEAs Methane Tracker and various reports Roser, 2020a, 2020b;IEA, 2021;Saunois et al. 2020;. The studies do not typically consider the points made above, namely (1) the higher GWP 20 for methane compared with coal or (2) the natural CO 2 uptake of about 50%. The authors do not disagree with these studies on the comparisons made for gas versus coal, but their calculation shows the situation to be less favourable for natural gas than suggested, due to the fugitive methane from other identified sources. This conclusion is equally valid for GWP 100 and even for fugitive methane arising from methane produced for combustion alone.
The following references provide support for the authors' views, namely, that natural gas in various forms is likely to generate higher emissions than coal. ➤ Bloomberg (2021), Sarah Smith, programme director for super pollutants at Clean Air Task Force, 'World leaders are starting to recognize that curbing methane is the only clear strategy to cut warming over the next two decades'. ➤ CNN (2021), after the release of the IPPC AR6 Report: '… for the first time, the UN climate change report emphasized the need to control a more insidious culprit: methane, an invisible, odor-less gas with more than 80 times more warming power in the near-term than carbon dioxide'. ➤ Clean Energy Wire (2021) Additional resources in English and German are referenced below.
Howarth (2019) points out that 'While methane emissions are often referred to as "leaks", some of the emissions include purposeful venting, including the release of gas during the flowback period immediately following hydraulic fracturing, the rapid release of gas from blowdowns during emergencies but also for routine maintenance on pipelines and compressor stations, and the steadier but more subtle release of gas from storage tanks and compressor stations to safely maintain pressures'. Alvarez, R.A. et al. 2018. Assessment of methane emissions from the U.S. oil and gas supply chain. https://www.science.org/doi/10.1126/science.aar7204 CCWA. 2019. About LNG in Australia: "Gas is not 'cleaner' than coal". p. 43. https://apo.org.au/sites/default/files/resource-files/2019-11/apo-nid266691.pdf