5. Anthropogenic methane sources, emissions and future projections
5.5 Use of anthropogenic methane emission scenarios in climate models
Chapter 8 presents the results of two climate modeling experiments to assess the effects on surface air temperature of the maximum technically feasible implementation of existing methane control technology, either globally or in the eight Arctic nations only. For these exercises, the GAINS scenario ECLIPSE v4a (ECLIPSE 2012) was used. The scenario ECLIPSE v5 (ECLIPSE 2014) only became available in April 2014, which was too late for it to be included in the climate modelling experiments for the present assessment. For comparison, the results of both scenarios are displayed in Fig. 5.9. The ECLIPSE (2012) scenario combines a global energy scenario to 2030 from IEA World Energy Outlook 2011 (IEA 2011a) with a global energy scenario to 2050 from the POLES model (Russ et al. 2009). The ECLIPSE (2014) scenario uses a consistent energy scenario to 2050 from IEA
Energy Strategies Perspectives 2012 (IEA 2012) and attributes shares of gas produced to conventional or unconventional gas using country-specific trends from the IEA (2011b).
Global methane emissions increase more rapidly in the ECLIPSE (2014) scenario than the ECLIPSE (2012) scenario due to a stronger increase in global gas consumption (partly driven by increased extraction of shale gas in the USA and Canada), and the introduction in the GAINS model of higher emission factors for unconventional than for conventional gas extraction. The MFR scenarios (ECLIPSE 2012, 2014) assume uptake of technical control options, which almost exclusively address methane emissions, without affecting emissions of other species contributing to radiative forcing. The only option included which affects emissions of other species, is a ban on the burning of agricultural waste residuals. This source contributes, however, to less than 1% of global methane emissions in the CLE scenarios (ECLIPSE 2012, 2014).
5.6
Conclusions
5.6.1
Key findings
This chapter reviews recent global assessments of anthropogenic methane emissions, their expected future development and estimated reduction potentials. Because methane is a gas which mixes rapidly in the global atmosphere, it is of interest to review emissions at the global scale as well as for the area covered by the eight Arctic nations. The following key findings have been identified:
• Bottom-up emission inventories agree fairly well in terms of the overall magnitude of global anthropogenic methane emissions in recent years, that is, about 300 Tg CH4 in 2000 and between 320 and 346 Tg CH4 in 2005. However, the relative contributions from the different source sectors differ markedly between inventories, which can be taken as an indication of high uncertainty within existing emission inventories despite the relatively close agreement between them in terms of total emissions.
• Without further implementation of control policies addressing methane than currently adopted, global anthropogenic methane emissions are estimated to increase to between 400 and 500 Tg CH4 in 2030 and between 430 and 680 Tg CH4 in 2050. Primary drivers for the expected emission increase are increased coal production in China and extended shale gas extraction in the USA and Canada, activities which are known to release fugitive methane emissions.
• With maximum technically feasible implementation of existing control technology, the estimated reduction potential for global anthropogenic methane emissions amounts to about 200 Tg CH4 in 2030, which is almost 50% below baseline emissions. The control technologies assessed to have the greatest reduction potentials are extended recovery of associated gas from oil production, control of fugitive leakages from gas production, transmission and distribution, extended separation, recycling and treatment of biodegradable waste instead of landfill disposal, extended pre-mining degasification of coal mines, and the implementation of ventilation air oxidizers on shafts from underground coal mines.
Fig. 5.9 Scenarios for global anthropogenic methane emissions from the GAINS model (ECLIPSE 2012, 2014). The three ECLIPSE (2012) scenarios were used in the model experiments presented in Ch. 8.
MFR (ECLIPSE, 2014) MFR (ECLIPSE, 2012)
MFR in Arctic 8 only ‘MFR-AC8’
(ECLIPSE, 2014)
MFR in Arctic 8 only ‘MFR-AC8’
(ECLIPSE, 2012) CLE (ECLIPSE, 2014)
CLE (ECLIPSE, 2012) Tg CH4
0 100 200 300 400 500 600
2050 2040
2030 2020
2010 2000
• External factors, in particular the development of the future price of gas, could have significant effects on the future cost of reducing methane emissions and on the need for further policies to stimulate such reductions. The reason is that many measures to reduce methane emissions involve gas recovery or reduced gas leakage, which means potential opportunities to utilize the recovered gas as a source of energy.
• With current policies addressing methane emissions, the eight Arctic nations are estimated to contribute about a fifth of global anthropogenic methane emissions.
• As a single world region, the eight Arctic nations emit more anthropogenic methane and have a larger technical abatement potential than any other major world region (e.g.
Latin America, Middle East, Africa or China).
• The maximum technically feasible reduction of anthropogenic methane in Arctic nations in 2030 is estimated at 63% below baseline emissions or about a quarter of the entire global reduction potential. Within this reduction potential, measures related to fugitive methane emissions from shale gas extraction in the USA and Canada, reduced venting of associated gas from oil production in Russia, and reduced leakage from gas pipelines and distribution networks in all three countries, have the greatest potential to contribute to reduced methane emissions in Arctic nations.
5.6.2
Recommendations
As a major contributor to global anthropogenic methane emissions and with a considerable potential to reduce methane emissions by employing existing technology, the eight Arctic nations are in a good position to contribute significantly to emission reductions in global methane emissions. For the same reason, the Arctic nations could also make important contributions towards reducing uncertainty in emission estimates and abatement potentials by supporting improvements in existing methane measurement networks.
• Increase the number and type of systematic on-site measurements and make results publically available to help reduce the large uncertainty in global methane emission estimates. This would be particularly important for the potentially substantial fugitive methane emissions from oil and gas systems for which very few direct measurements exist that are source attributed and representative for different types of hydrocarbons in different world regions.
• Support a continuous dialogue between developers of top-down and bottom-up emission estimates in order to resolve the current unexplained divergence in global methane estimates. Currently, the observed year-to-year variation in methane concentration in the atmosphere over the past few decades cannot be explained by global anthropogenic (and natural) emission inventories. This is a problem because historical emission inventories are the basis for future projections.
Acknowledgments
The authors are grateful for valuable comments and suggestions from Reino Abrahamsson (Swedish Environmental Protection Agency), Dominique Blain (Environment Canada), Jordan Guthrie (Environment Canada), Jennifer Kerr (Environment Canada), Andrei Kiselev (Main Geophysical Observatory, Russia), Paal Kolka Jonsson (The Environment Agency of Iceland) and Christoph Wöll (The Environment Agency of Iceland).