摘要
京都議定書規範附件一國家自2008年至2012年的溫室氣體排放數量，與各國1990年的排放水平相比至少減少5%。附件一國家得以利用國際排放權交易機制，達成其排放減量目標。隨著京都議定書即將到期，且開發中國家逐漸成為溫室氣體的主要排放國，擴大參與國家的排放權交易機制為研究重點。文獻探討後京都時期的擴大參與國際排放權交易，並未強調附件一國家於前期減量行動對於其後京都時期決策行為的影響：與非附件一國家相較，附件一國家先行參與減量，經由「做中學」效果，使附件一國家於後京都時期享有較低的邊際減量成本。本文將附件一國家前期減量行動對後期邊際減量成本減少的效果納入考量，建立完全訊息的兩期兩階段賽局，並利用數值模擬，探討在後京都時期的擴大參與排放權交易下，國家的跨期行為對於排放交易機制的影響。 針對附件一國家於京都議定書規範下的減量決策，本文假設二種情境：情境一、假設所有附件一國家均具遠見，各國於前期決策時，一併考量後京都時期擴大參與交易架構下各自的成本；情境二、假設所有附件一國家均不具遠見，則各國於前期決策時，僅針對各自的當期成本進行決策。附件一國家是否具有遠見的差異將影響其前期的行為決策，進而因「做中學」效果影響國家後期邊際減量成本。因此本文續探討於後京都時期擴大參與交易機制架構下，享有「做中學」效果的附件一國家與未享有此效果的非附件一國家的減量決策及跨期影響效果。 由理論模型可知，當附件一國家具遠見且排放權交易市場為完全競爭時，由於各國決策時已考量其前期行為對於後期的影響，因此各國的邊際成本無法經由排放權價格調和而趨於一致，第一期的排放權交易不具有成本有效性。與情境二相較，由於國家於情境一考量前期決策對後期的影響，因此具有較顯著「做中學」效果的附件一國家將於第一期選擇較多的減量水準；反之，附件一國家具有較不顯著的「做中學」效果，將選擇較低的減量水準。附件一國家前期的減量水準將影響後期擴大參與的排放權價格：當附件一國家前期的減量水準減少，將使此國家於後期增加對於排放權的需求，進而造成後京都時期排放權價格增加。 由於國際排放權市場並未存在具強制力的跨國機關核配排放權數量，各國乃基於自利誘因選擇初始排放權配額。當附件一國家具遠見時，考量前期的決策對於後期的影響，與情境二相較，國家將於第一期選擇較少的排放權配額。本文經由數值模擬，發現第一期與第二期的全球累積排放數量均因附件一國家存在遠見而明顯較少。與情境二相較，當附件一國家於前期具有遠見時，國家於第一期享有較低的損害成本，後京都時期全球進行二氧化碳減量的總成本亦較低。
並列摘要
Because the end to the first commitment period of the Kyoto Protocol is quickly approaching, there is an increasing interest in the expanding international emission trading (IET) system consisting of the Annex-I countries and non Annex-I countries. This thesis develops a two-period, two-stage sequential game along with a numerical application for IET to explore the intertemporal interactions among participating countries. Central to the analysis is that the Annex-I countries would enjoy the learning-by-doing (LBD) effect of abatement, which leads to a lower cost of abatement in the post-Kyoto period. We explore how the Annex-I countries’ LBD effects in the first commitment period affect countries’ decisions in the post-Kyoto period. We also analyze how the expanding participation in the post-Kyoto IET system affects the Annex-I countries’ behavior in the first commitment period and that in the subsequent period. In the first commitment period under the Kyoto period, two cases are assumed to capture the real world situation: one is the farsighted case; the other is the shortsighted case. In the farsighted case, the Annex-I countries make decisions in the Kyoto period with considering the costs in the Kyoto period and the post-Kyoto period, including the cost reduction effects from LBD; while in the shortsighted case, the Annex-I countries make decisions with considering costs in the Kyoto period. In the post-Kyoto period, under the expanding participation framework, the Annex-I countries and non Annex-I countries make decisions to minimize their costs in the period with the Annex-I countries’ cost reduction effects from LBD. The main findings of the thesis are summarized as follows. In the farsighted case, with considering the total costs in two periods, the Annex-I countries pay attention on the intertemporal impacts on the costs in the post-Kyoto period when choosing emissions in the Kyoto period. Countries’ marginal abatement costs might not be coordinated by the market mechanism; thus, the IET system in the Kyoto period is cost-ineffective. The Annex-I countries with significant cost effects from LBD in the Kyoto period will choose higher abatements (lower emissions); while countries with insignificant cost effects from LBD choose lower abatements (higher emissions), as compared with their counterparts in the shortsighted case. The Annex-I countries’ emissions in the Kyoto period affect the permit price in the post-Kyoto period. If an Annex-I country has lower abatements in the Kyoto period, then her permit demand in the post-Kyoto period will increase; accordingly leading to a higher permit price in the post-Kyoto period. Similar to the emissions, the Annex-I countries’ emission permits choices are affected by the farsightedness. In the farsighted case, when choosing emission allowances in the Kyoto period, the Annex-I countries focusing on the damage costs in the post-Kyoto period; thus, they choose lower emission allowances in the Kyoto period, as compared with the shortsighted case. Because our theoretical model can not give a definite conclusion regarding the environmental efficiency of IET system under different circumstances (i.e., the farsighted or shortsighted cases), we conduct a numerical application to acquire more concrete insights. In the farsighted case, the Annex-I countries choose fewer emission allowances in the Kyoto period with considering the costs in the post-Kyoto period; thus, the global emission in the Kyoto period is lower than that in the shortsighted case. In the post-Kyoto period, the overall emission in the farsighted case is much less than that in the shortsighted case. We conclude that countries’ farsightedness in the Kyoto period results in lower emissions in two periods. In the farsighted case, the Annex-I countries have lower damage costs in the Kyoto period than those in the shortsighted case. In the post-Kyoto period, participating countries’ costs are lower in the farsighted case than their counterparts in the shortsighted case. The above results show that the Annex-I countries’ farsightedness result in the Annex-I countries’ lower damage costs in the Kyoto period and a lower global cost in the post-Kyoto period.