環境資訊中心外電；姜唯 翻譯；林大利 審校；稿源：Carbon Brief 前言：國際能源署（IEA）11月13日發表2019年《世界能源展望》報告。810頁報告的特點在於「承諾政策情境」（Stated Policies Scenario, STEPS），反映政府已經說出口的政策的效果──風能和太陽能的激增將使再生能源滿足全球能源需求的大部分成長。但是煤炭的平穩發展，加上對石油和天然氣的需求不斷增加，全球排放量在到2040年的展望期內將繼續上升。 相對地，報告的「永續發展情境」（Sustainable Development Scenario, SDS）描繪出有50％機率將升溫限制在1.65°C內所需的條件，IEA表示這是「完全符合巴黎協定」的情況──SDS需要投資「大量重新分配」，從化石燃料轉向效率和再生能源、淘汰全球約一半的燃煤電廠，以及全球經濟的其他變化。
二氧化碳排放量
（）在STEPS之下，全球來自能源的碳排放量將在2018年創紀錄後繼續上升，本世紀很可能升溫2.7°C以上。 下表中的黑色虛線表示此排放軌跡。
相反地，SDS（紅色粗線）之下碳排迅速下降，比2010年還下降17％，2040年下降48％，2050年下降68％。IEA說，如此可在2070年實現淨零排放，並且有50％的機會將升溫限制在1.65°C，或66％的機會停在1.8°C。
這條軌跡的積極度比大多數1.5°C途徑要低，升溫沒有或是僅一小段時間超標（下圖中的黃線）。 政府間氣候變遷專門委員會（IPCC）在其1.5°C特別報告中表示，1.5°C途徑需要在2030年將碳排降至2010年水平的45％，並在2050年達到淨零。
過去（實線）和未來各種不同情境下，來自能源和工業的全球二氧化碳排放量：IEA STEPS（黑色虛線）、IEA SDS（粗紅線）、IPCC升溫1.5℃內途徑，沒有或有限的升溫度超標（細黃線）、IPCC升溫超過1.5C途徑（藍色）以及IPCC升溫2C途徑（灰色）。低於零的值表示負排放，即來自能源和工業的二氧化碳增加量少於移除量，這裡主要是指有碳捕獲和儲存（BECCS）的生物能。資料來源：國際能源署《 2019年世界能源展望》和Carbon Brief對IPCC 1.5℃暖化特別報告的簡要分析。圖片由Carbon Brief用Highcharts繪製。
根據IEA資料，SDS「使全球氣溫上升控制在遠低於2°C……並力求控制在1.5°C以內，完全符合《巴黎協定》目標」。還提供了兩種表現可以超越SDS，同時升溫保持在1.5°C以下的選擇。
「力求」不一定是實現目標，而是朝著目標前進，或者是非常接近1.5°C－只要有額外的行動。
除了WEO中心觀點STEPS外，巴黎協定中所謂的「非常接近」也是飽受非政府組織、科學家、商業團體和其他組織批評的語言。他們今年四月寫信呼籲IEA模擬出有66%機率將升溫限制在1.5°C的情境。
這封信的其中一位作者、倫敦帝國理工學院格蘭瑟姆研究所氣候變遷和環境講師羅傑爾（Joeri Rogelj）博士說，SDS和1.5°C不一致，和《巴黎協定》也有些面向不同。
羅傑爾是IPCC 1.5°C特別報告第二章的協調主要作者，也是IPCC即將發布的第六次評估報告中第一工作組的主要作者。
他告訴Carbon Brief，巴黎協定的「力求1.5°C」至少有兩種可能的解釋，一種是將峰值升溫限制在1.5°C，另一種是可以超過再降回。「把錯過目標納入計畫當中，不能合理解釋成完全符合《巴黎協定》，」羅傑爾說。
他還指出了協定的第4條，致力於在人為碳排放源與所有溫室氣體匯之間達到「平衡」。要實現這個目標可能需要淨負碳排，SDS沒有達成這一點的詳細途徑。
負碳排可以透過技術解決方案實現，如帶有碳捕集與封存的生物能源（BECCS），也可透過自然氣候解決方案達成，如綠化。
IEA表示，負排放確實是SDS之下達成1.5°C的一種方法，總共需要清除大約3000億噸的二氧化碳（GtCO2）才能彌補這個差距。然而IEA也承認，大規模部署負碳排設備的永續性和可交付性的確存在隱憂。
WEO說：
考慮到負排放技術的問題，構建一個超越SDS、2050年實現零碳排放，並有50％的機率將升溫限制在1.5°C，而無需依賴淨負碳排的情境是有可能的。
（這個情境已經有人做出，收錄在IPCC的1.5°C報告和上圖中。）
IEA表示，要超越SDS，全世界必須正面對抗那些最困難的領域，如航空、重工業和建築供熱，包括全面性的建築改造、工業過程新技術的開發和改造。
IEA表示，這「不只是擴大SDS中的變革而已」，而是要「面對非常困難且難以克服的挑戰」，有一些領域需要社會大眾的接受度和行為改變：
「這不是能源業內部就能做到的事，而是整個社會的任務……需要跨非常多領域進行大規模變革，這將直接影響幾乎每個人的生活。」
雖然有點挑戰性，但如果IEA能建構出1.5°C情境，政策規劃人員可以參考IEA模型來瞭解各種能源和氣候選擇。隨著各國政府根據《巴黎協定》重新考慮其氣候承諾，並在2020年推出新一輪的國家自主減排計畫，這個參考資料將顯得很重要。
煤炭的變化
報告內有去年版本至今的各種變動，反映相對於基準年的變化－2018年需求增加力道異常強勁－以及新增或修訂的政策。
IEA再次下調了STEPS下的煤炭需求前景，如下圖所示（紅線）。但是煤炭近期前景提高了，部分原因是中國重新依賴高污染產業來支撐增長緩慢。
全球煤炭需求歷史（黑線，百萬噸石油當量）和IEA前一版中心觀點情境的未來成長（藍色色塊）。今年的STEPS以紅色標示，SDS以黃色標示。資料來源：國際能源署《 2019年世界能源展望》和前一版報告。Carbon Brief使用Highcharts繪製。
照STEPS的計畫和政策，儘管近期需求有所增長，今年燃煤用量將會低於2014年的峰值，但仍遠高於SDS之下、暖化遠低於2°C途徑的水準（上圖黃線）。
STEPS之下，美國和歐盟等已開發經濟體煤炭用量快速下降，但印度需求增長是保持全球煤炭用量穩定的關鍵因素之一。
印度這波成長的部分原因是大量新火力發電廠興建中，到2040年將打造出232GW的容量，成長一倍，佔全球新增容量的1/3。
IEA表示，如果電池儲存成本的下降速度快於預期，印度的煤電容量成長將被「大幅削減」。 IEA表示，太陽能和廉價的儲存技術可以「重塑印度電力結構的演變」，並提供「非常引人注目的經濟和環境主張」。
印度的高壓電塔。照片來源： 。
值得注意的另一點是，印度目前燃煤容量只有85GW，IEA預計的新燃煤容量卻高達232GW，其中有1/4已經被凍結多年。
自2010年以來，由於廉價再生能源的競爭、公用事業公司財務困境和公眾的反對，有額外510GW的新煤電廠計畫被取消。
此外，印度政府一再高估了電力需求的增長，現有煤電容量的運行時間不到2/3。2019年至今的數據顯示，印度煤炭發電量可能正在下降。
印度政府最近宣布了一個相當積極的目標，太陽能、風能和生質能的容量要達到450GW，最快2030年達成。IEA的STEPS到2030年僅增加344GW。根據近期Carbon Brief的分析，如果能夠達到這個目標，那麼風能、太陽能和其他低碳能源可以在不增加新煤電的情況下，滿足日益增長的需求。（2/3，未完待續）
‘Profound shifts’ underway in energy system, says IEA World Energy Outlook (2/3) by Simon Evans
CO2 emissions
In the STEPS, global CO2 emissions from energy would continue to rise from the they reached in 2018, putting the world on track for upwards of 2.7C of warming this century. This emissions trajectory is shown with the dashed black line in the chart, below.
In contrast, CO2 declines quickly in the SDS (thick red line) to 17% below 2010 levels by 2030, 48% by 2040 and 68% by 2050. According to the IEA, this is “on course for net-zero emissions by 2070” and corresponds to a 50% likelihood of limiting warming to 1.65C, or a 66% chance of 1.8C.
This trajectory is less ambitious than most pathways to 1.5C with no or limited overshoot (yellow lines, below). In its on 1.5C, the (IPCC) said this would need CO2 to fall 45% below 2010 levels by 2030 and to net-zero by 2050.
Global CO2 emissions from energy and industrial processes in the past (solid black line) and under a range of different scenarios for the future: IEA STEPS (dashed black); IEA SDS (thick red line); IPCC pathways limiting warming to 1.5C this century with no or limited temperature overshoot (thin yellow lines); pathways to 1.5C with high overshoot (blue); and IPCC 2C pathways (grey). Values below zero indicate negative emissions, where residual CO2 from energy and industry is more than offset by removals, here primarily bioenergy with carbon capture and storage (BECCS). Source: IEA and Carbon Brief analysis of the for the IPCC of warming. Chart by Carbon Brief using .
According to the IEA, the SDS charts “a path fully aligned with the by holding the rise in global temperatures to ‘well below 2C…and pursuing efforts to limit [it] to 1.5C’”. It also offers two options for going beyond the SDS to keep warming below 1.5C.
This form of words implies either that “pursue” means to head towards a goal, without necessarily reaching it, or that the SDS is aligned with 1.5C – so long as it is accompanied by additional action.
Along with the WEO’s central focus on the STEPS pathway, the statement on Paris “alignment” is at the heart of from a group of NGOs, scientists, business groups and others. In an , they called for the IEA to develop a scenario with a 66% chance of limiting warming to 1.5C.
One of the letter’s authors, , a lecturer in climate change and the environment at the , says the SDS is “inconsistent with 1.5C and several aspects of the Paris Agreement”.
Rogelj was a coordinating lead author on chapter two of the IPCC and is a for working group one on the IPCC’s forthcoming .
He tells Carbon Brief that there are at least two potential interpretations of the Paris ambition to “pursue efforts towards 1.5C”. One is that of limiting peak warming to 1.5C and the other is overshooting this level before returning below 1.5C, Rogelj says: “Planning to simply miss it is not a reasonable interpretation for a scenario that wants to be fully aligned with the Paris Agreement.”
He also points to of the deal, which commits to reaching a “balance” between human sources and sinks of all greenhouse gases. This goal is likely to require net-negative CO2, for which the SDS provides no detailed pathway.
Negative CO2 emissions could be provided via , such as (BECCS), or using “”, such as afforestation.
The IEA says that negative emissions do indeed offer one way that the SDS could become aligned to a 1.5C limit. A cumulative total of around 300bn tonnes of CO2 (GtCO2) would need to be removed to bridge this gap, it adds. There are over the sustainability and deliverability of such extensive deployment, however, and these are acknowledged by the IEA.
The WEO says:
“[I]t would be possible in the light of concern about [negative emissions technologies] to construct a scenario that goes further than the Sustainable Development Scenario and delivers a 50% chance of limiting warming to 1.5C without any reliance on net-negative emissions on the basis of a zero carbon world by 2050.”
[Other groups have developed a limited of that already do this, which are included in the IPCC’s and the figure above.]
To go beyond its SDS, the IEA says the world would need to tackle “hard to abate” sectors, such as aviation, heavy industry and heat for buildings. This would include near-universal building retrofits and the development and retrofitting of new technologies for industrial processes.
The IEA says this “would not amount to a simple extension” of the changes in the SDS, instead “pos[ing] challenges that would be very difficult and very expensive to surmount.” It adds that tackling some of these areas would require social acceptance and behavioural change:
“This is not something that is within the power of the energy sector alone to deliver. It would be a task for society as a whole…Change on a massive scale would be necessary across a very broad front, and would impinge directly on the lives of almost everyone.”
If the IEA were to develop a 1.5C scenario, despite the challenges it would present, then the agency’s modelling could be used by policymakers to inform their energy and climate choices. Such guidance would be pertinent as governments reconsider their climate pledges under the Paris Agreement, with a fresh round of “” due in 2020.
Coal changes
The outlook includes various changes since last year’s edition, reflecting shifts in the base year – there was growth in demand in 2018 – and new or amended policy.
As a result, the IEA has once again revised down its outlook for coal demand in the central STEPS pathway, as the chart below shows (red line). However, it has also raised its near-term outlook for coal, in part due to China’s renewed industries to prop up flagging growth.
Historical global coal demand (black line, millions of tonnes of oil equivalent) and the IEA’s previous central scenarios for future growth (shades of blue). This year’s STEPS is shown in red and the SDS is in yellow. Source: IEA and previous editions of the outlook. Chart by Carbon Brief using .
Despite the near-term increase in expected demand, this year’s outlook affirms that coal use would remain below the global peak reached in 2014, if stated plans and policies are met as per the STEPS. Nevertheless, this would leave coal demand significantly above the level in its SDS, where warming is limited to well-below 2C (yellow line, above).
According to the STEPS, rising is one of the key factors holding global coal use steady, despite rapid falls in developed economies, such as the US and EU.
Part of the reason for this increase in India is a large expected buildout of new coal-fired power stations, with 232GW of capacity built by 2040 in the STEPS, roughly doubling its and accounting for a third of global additions.
The IEA says India’s coal capacity growth could be cut “sharply”, if declines in the cost of battery storage are faster than expected. Solar and cheap storage could “reshape the evolution of India’s power mix”, the IEA says, offering a “very compelling economic and environmental proposition”.
It is also worth comparing the 232GW of new coal capacity expected by the IEA, with India’s current pipeline of , of which a quarter has been frozen in construction for years.
Another 510GW of new coal has been cancelled since 2010 due to competition from cheaper renewables, financial distress at utility firms and public opposition.
In addition, the Indian government has electricity demand growth, meaning existing coal capacity is running less than two-thirds of the time. Moreover, data for 2019 to date suggests India’s electricity .
The Indian government recently a highly ambitious target for solar, wind and biomass capacity to reach 450GW, potentially as soon as 2030, when the IEA STEPS outlook sees just 344GW having been added. If this target is met, then wind, solar and other low-carbon sources could largely meet rising demand without new coal, according to recent .
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作者
如果有一件事是重要的，如果能為孩子實現一個願望，那就是人類與大自然和諧共存。
於特有生物研究保育中心服務，小鳥和棲地是主要的研究對象。是龜毛的讀者，認為龜毛是探索世界的美德。
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