Regional variation in the effectiveness of methane-based and land-based climate mitigation options
Regional variation in the effectiveness of methane-based and land-based climate mitigation options
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DOI：
10.5194/esd-2020-24
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发表时间：
2020-06
影响因子：
7.3
通讯作者：
G. Hayman;E. Comyn‐Platt;C. Huntingford;A. Harper;Tom Powell;P. Cox;William J. Collins;C. Webber;J. Lowe;S. Sitch;J. House;J. Doelman;D. V. van Vuuren;S. Chadburn;E. Burke;N. Gedney
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文献类型：
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作者：
G. Hayman;E. Comyn‐Platt;C. Huntingford;A. Harper;Tom Powell;P. Cox;William J. Collins;C. Webber;J. Lowe;S. Sitch;J. House;J. Doelman;D. V. van Vuuren;S. Chadburn;E. Burke;N. Gedney
摘要。按照《巴黎协定》的规定，要避免全球变暖超过1.5或2°C的情景，可能需要通过造林-再造林（AR）和具有碳捕获和储存的生物质能（BECCS）等方法，在减少人为温室气体排放的同时，增加负排放。我们使用JULES陆地表面模型与倒置的IMOGEN气候模拟器相结合，来研究达到《巴黎协定》规定的1.5°C或2°C升温目标的缓解情景。具体而言，在IMOGEN-JULES框架内，我们将重点关注并描述陆基（BECCS和/或AR）和人为甲烷（CH4）排放减缓的全球和区域有效性，分别并结合人为化石燃料二氧化碳（CO2）排放预算（AFFEBs）到2100年。我们使用来自IMAGE综合评估模型的一致数据和社会经济假设来评估第二条共享社会经济路径（SSP2）。该分析包括湿地和永久冻土融化产生的甲烷和碳-气候反馈的影响，我们之前已经表明，这是对AFFEBs的重大限制。在全球范围内，人为甲烷排放的减缓对人为化石燃料排放预算有很大影响，可能抵消（即允许额外）188-212亿吨碳的二氧化碳排放。这是因为(a)甲烷的直接和间接辐射强迫减少，以应对排放量的降低，从而减少大气中甲烷的浓度，以及(b)碳循环变化导致陆地和海洋通过以二氧化碳为基础的施肥增加吸收。减少甲烷在任何地方都是有益的，特别是对印度、美国和中国等主要的甲烷排放地区。陆基缓解有可能在全球抵消51-100亿吨C，这一大范围反映了与BECCS相关的假设和不确定性。减少甲烷和实施BECCS的范围适用于1.5°C和2°C的升温目标。也就是说，无论最终社会的目标是稳定的变暖水平中的哪一个，甲烷和陆基情景的减缓潜力是相似的。此外，有效性和首选土地管理策略（即AR或BECCS）都具有很强的区域依赖性。进一步的分析表明，广泛的BECCS可能对若干地区的水安全产生不利影响。虽然首要要求仍然是减少化石燃料排放，但我们的研究结果强调了减少甲烷排放的潜力，使巴黎气候目标更容易实现。
Abstract. Scenarios avoiding global warming greater than 1.5 or 2 ∘C, as stipulated in the Paris Agreement, may require the combined mitigation of anthropogenic greenhouse gas emissions alongside enhancing negative emissions through approaches such as afforestation–reforestation (AR) and biomass energy with carbon capture and storage (BECCS). We use the JULES land surface model coupled to an inverted form of the IMOGEN climate emulator to investigate mitigation scenarios that achieve the 1.5 or 2 ∘C warming targets of the Paris Agreement. Specifically, within this IMOGEN-JULES framework, we focus on and characterise the global and regional effectiveness of land-based (BECCS and/or AR) and anthropogenic methane (CH4) emission mitigation, separately and in combination, on the anthropogenic fossil fuel carbon dioxide (CO2) emission budgets (AFFEBs) to 2100. We use consistent data and socio-economic assumptions from the IMAGE integrated assessment model for the second Shared Socioeconomic Pathway (SSP2). The analysis includes the effects of the methane and carbon–climate feedbacks from wetlands and permafrost thaw, which we have shown previously to be significant constraints on the AFFEBs. Globally, mitigation of anthropogenic CH4 emissions has large impacts on the anthropogenic fossil fuel emission budgets, potentially offsetting (i.e. allowing extra) carbon dioxide emissions of 188–212 Gt C. This is because of (a) the reduction in the direct and indirect radiative forcing of methane in response to the lower emissions and hence atmospheric concentration of methane and (b) carbon-cycle changes leading to increased uptake by the land and ocean by CO2-based fertilisation. Methane mitigation is beneficial everywhere, particularly for the major CH4-emitting regions of India, the USA, and China. Land-based mitigation has the potential to offset 51–100 Gt C globally, the large range reflecting assumptions and uncertainties associated with BECCS. The ranges for CH4 reduction and BECCS implementation are valid for both the 1.5 and 2 ∘C warming targets. That is the mitigation potential of the CH4 and of the land-based scenarios is similar for regardless of which of the final stabilised warming levels society aims for. Further, both the effectiveness and the preferred land management strategy (i.e. AR or BECCS) have strong regional dependencies. Additional analysis shows extensive BECCS could adversely affect water security for several regions. Although the primary requirement remains mitigation of fossil fuel emissions, our results highlight the potential for the mitigation of CH4 emissions to make the Paris climate targets more achievable.