報告書番号

Y97006

タイトル（和文）

温暖化対策の時間的柔軟性に関する考察

タイトル（英文）

TIME FLEXIBILITY IN CONTROLLING GHG EMISSIONS:EVIDENCE FROM LONG-TERM ELECTRICITY GENERATION MIX MODEL

概要 （図表や脚注は「報告書全文」に掲載しております）

コスト効率的な温暖化対策を行うために温暖化問題の大気物理が持つ時間的柔軟性を利用する方法について，定量的に検討した。主な結果は以下の通り。１．長期的な濃度増分目標下でのコスト最小の排出抑制戦略において，排出抑制限界費用の従う表式を導いた。ＣＯ２の限界費用は概ね割引率で上昇する指数関数になる。２．時間的柔軟性を利用することで，（１）私的な割引率，（２）ＣＯ２大気中濃度の自然減少，（３）既存設備の寿命，（４）低ＣＯ２排出技術の開発見通し，等を考慮して，環境影響を増すこと無しに，より無理の少ない排出削減計画が策定できる。３．電源構成モデル試算によると，２０３０年ごろまでの範囲で時間的柔軟性を利用することによって，排出削減費用が半分近くに軽減されうることが示された。電力供給部門の温暖化防止への取り組みは重要であるが，技術経済的な観点からは，時間的柔軟性を活用することが望ましい。

概要 （英文）

THE NATURE OF GLOBAL CLIMATE CHANGE PERMITS SOMETIME FLEXIBILITY FOR CO2 MITIGATION. THIS FLEXIBILITY IS TAKEN INTOACCOUNT BY CHANGING MITIGATION SCHEME FROM YEARLY TARGET , WHICH LIMITS CO2 EMISSIONS EACH YEAR, TO LONG-TERM TARGET , WHICH HAS THE CONSTRAINT THAT THE INCREMENT IN CO2 CONCENTRATION AT THE LAST PLANNING YEAR IS SET EQUAL TO THE CORRESPONDING YEARLY TARGET SCHEME. WHILE IT IS PROBLEMATIC TO ACHIEVE FLEXIBILITY IN THE WORLD AND LONG-TERM CONTEXT, WHERE FORMIDABLE ISSUES SUCH AS INTER-GENERATIONAL AND INTERNATIONAL EQUITY EXIST,THERE MAY BE A MORE REALISTIC POSSIBILITY FOR A SPECIFIC SECTOR OF A SPECIFIC COUNTRY TO USE FLEXIBILITY. ANALYSIS BY BOTH ANALYTIC APPROACH AND NUMERICAL MODEL FOUND THE FOLLOWING: (1)THE ANALYTIC SOLUTION FOR THE MARGINAL MITIGATION COSTS IS AN INCREASING FUNCTION WITH TIME. THE TIME CONSTANT IS DERIVED AS A COMBINATION OF THE GAS LIFETIME INTHE ATMOSPHERE AND THE DISCOUNT RATE OF THE PLAYER. (2)IN THE LONG-TERM TARGET SCHEME, PLAYERS CAN SET THEIR OWN GHG CONTROL PLANS WITH TIME FLEXIBILITY. THE PLAN CAN AND MUST TAKE THE FOLLOWING FACTORS INTO ACCOUNT: (A)PRIVATE DISCOUNT RATE, (B)NATURAL GHG DECREASE SUCH AS CARBONUPTAKE BY OCEAN, (C)CAPITAL TURNOVER TIME, (D)PROSPECTS FOR R&D OF LOW-GHG TECHNOLOGIES. IN CONTRAST, EMISSION REGULATION WITHOUT FLEXIBILITY( YEARLY TARGET ) MAY RESULT IN HIGHER COSTS. (3)ANALYSIS FOR THE JAPANESE UTILITY SECTOR SHOWS THAT A LONG-TERM TARGET SCHEME WITH A TIME RANGE OF 40 YEARS (FROM 1994 TO 2034) WOULD READY HALVE MITIGATION COSTS,WHILE KEEPING THE ENVIRONMENTAL IMPACT UNCHANGED FROM THE CORRESPONDING YEARLY TARGET SCHEME. WHILE MITIGATION BY THE ELECTRICITY SUPPLY SECTOR IS IMPORTANT, IT DOES NOT NECESSARILY MEAN AN IMMEDIATE AND DRASTIC CO2 REDUCTION. TAKING ADVANTAGE OF FLEXIBILITY WOULD CONSIDERABLY REDUCE THE MITIGATION COSTS WITHOUT DOING ANY ADDITIONAL HARM TO THE GLOBAL CLIMATE.

報告者

キーワード