台灣邁向淨零碳排放減量路徑之研擬──引入碳預算之國家上位目標規劃

The Design of Net-zero Carbon Emissions Reduction Pathways for Taiwan: Carbon Targets Determination under the Considerations of Carbon Budget for the Country

為了讓台灣之溫室氣體（GHG）或二氧化碳（CO_2）的減量有清楚明確的上位目標，本文嘗試研擬了四種達淨零的不同減碳路徑，計算各減探路徑至階段性，如至2030年、2040年而至淨零年，所達成的減碳比例；進而，納入「聯合國政府間氣候變化專門委員會」（Intergovernmental Panel on Climate Change, IPCC）最新公布的2℃、1.7℃或1.5℃三種溫度上升的碳預算量（carbon budget）概念，選擇台灣在實務上相對操作性高的公平原則及各國統一減量相同比例原則，設計不同淨零減碳路徑及碳預算使用方式，除可進行多層面的比較與對照外，亦使台灣邁向淨零之路的國家上位減量目標得以清楚確立。關於各淨零減碳路徑之中程階段減至比基準年低的目標，相對有彈性的作法可如加拿大，法案中先明訂2030年的減量目標，而2030年後之目標、則在後續五年到來的前一年底明訂下一個階段的減量目標，如此在可掌握確實的條件與技術下，使所設定的減量目標有相對高之可達性。而台灣在控制溫渡上升不超過1.5℃、1.7℃及2.0℃下，至淨零年仍可有15.5億噸、26.35億噸及41.85億噸之碳預算，在本文所設計的不同淨零減量路徑下，使溫度上升不超過2.0℃比不超過1.5°Ｃ者之碳累積量高達4至13倍，因此，台灣如果無法立即有最大減量之貢獻使溫度上升不超過1.5℃，其他不同溫度上升之淨零減碳路徑與碳累積量處置可供台灣選擇有能力解決之適當組合。因此，納入碳預算考量，除可作為台灣淨零減量路徑之選擇外，亦扮演台灣相關碳捕捉及儲存技術研發、可否配合解決控制溫度上升在不同水準下的碳累積總量的重要角色。

In order to have definite in-stage emissions reduction targets to realize net zero greenhouse gases emissions (GHGs) or carbon dioxide (CO_2) reductions for Taiwan, the purposes of this study are to design different pathways for such achievement. The reduction percentages relative to the base-year-emissions target for the intermediate years, such as year 2030 or 2040, are determined. Moreover, with accounting for the newest carbon budget to have temperature increase within the limit of 2℃, 1.7℃, and 1.5℃ proposed by Intergovernmental Panel on Climate Change (IPCC), different combinations of emissions reductions pathways and the utilizations of carbon budget under equality principle and uniform relative reduction for all countries are compared. It will be more flexible to have the emissions reductions target clearly set for 2030 in law and subsequent reduction targets every 5-year after 2030 can be set one year before the target year. The advantage of such arrangement is to have relatively certain control of climate conditions and technology development progress for target to achieve. Under the control of temperature increase of 2℃, 1.7℃, and 1.5℃, the carbon budget for Taiwan is 1.55 billion tons, 2,635 billion tons, and 4.185 billion tons by the net-zero year, respectively. The cumulative emissions are about 4 times to 13 times more for temperature restricted to 2.0℃ than those restricted to 1.5℃. The selection of the best emissions reduction pathways should take into account the utilization of different amounts of carbon budgets. The consideration of carbon budget is not only essential information for selecting the proper emissions reductions pathways but also play an important role for incubating technology development of carbon capture and storage.