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its assessment of unconventional resources. Unlike previous energy systems projections, which have mostly focused on either specific topics or single objectives, the GEA report at- tempts to consider the technological feasibility and economic implications of meeting a range of sustainability goals (Riahi et al. 2012). The GEA assessment of different pathways sug- gests that it is technically possible to achieve improved en- ergy access, air quality, and energy security simultaneously, while avoiding dangerous climate change. Within each of the groups analysed, one pathway was se- lected as “illustrative” in order to represent alternative ways to move the energy system toward sustainability. Figure 1.5 shows the primary energy mix and carbon dioxide emis- sions historically, as well as an illustrative GEA pathway under the assumption of intermediate energy demand. The modelling results show a significant increase in natural gas consumption after 2020, with the share of gas in the primary energy mix reaching almost 50 per cent by 2050. The largest part of gas extraction shown in the figure re- sults from the development of unconventional resources. Figure 1.5 also illustrates the desired carbon dioxide emis- sions curve, peaking at 10 GtC in 2020 and declining rap- idly thereafter. To achieve this pathway, the rapid and simultaneous growth of many advanced technologies is required. A potentially important technology is carbon capture and storage. In- deed, the sustainability target of limiting global tempera- ture change to less than 2°C over preindustrial levels may

only be achievable with very substantive global efforts to ad- vance these technologies. In this pathway, the most attrac- tive option for generating electricity after 2020 is natural gas combined with carbon capture and storage. This option provides cleaner fuel supply chains, lower upstream green- house gas emissions, higher conversion efficiencies, and significantly lower capital intensity. Figure 1.4 also shows the historic H/C ratio and projects the ratio as far as 2050, based on the same GEA scenario as Figure 1.5. The expansion of natural gas use envisaged by this scenario (3 per cent annually) results in continuous improve- ment of the H/C ratio after 2015. We have chosen 2050 as a reasonable time horizon for discussing the implications of commercial gas hydrate production. As described in Chap- ter 3, it is generally accepted that technical barriers to gas hydrate extraction can be overcome before or by that date, and that national governments will be in a position to choose whether and how to exploit the resources at their disposal. Even as the commercial feasibility of gas hydrate extraction is demonstrated, technology alone will not determine the energy future. Economic, social, and environmental consid- erations, among others, will weigh in the decision. Recent decisions by Germany and Japan to move away from nuclear power as an energy source (see IEA 2011a) are examples. The time horizon of 2050 also provides enough time to consider alternative future pathways for the external factors that could have a major impact on how the gas hydrate option is utilized over the long term.

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