由於溫室氣體排放加快了全球暖化的進程，各國也因此頒布了各項抑制全球暖化與減少碳排放的協議，而為了達成減排目標，越來越多企業使用綠色金融工具，其中綠色債券的發行象徵著企業對可持續發展與降低碳排的承諾，也是綠色轉型專案的重要資金來源，因此近幾年發債比數與金額大幅增加，尤其以永續發展較成熟的歐盟為綠色債券發行的主要地區。
作為重要的綠色金融工具，綠色債券發行後是否能真的能減少碳排放，對緩和全球暖化做出貢獻，是一項值得探討的議題，而過去探討綠色債券發行與企業碳排放間關聯的文獻較為匱乏，也大多以總碳排放及全球區域作為研究。因此，為了避免不同區域造成的偏誤以及漂綠的可能，本文選擇以綠色債券規定嚴謹的歐盟地區為研究範圍，並額外加入直接碳排與間接碳排，以探討各項碳排強度在綠債發行後是否有不同的表現。
本文樣本期間取自從2018至2021年，碳排數據使用湯森路透Eikon-Refinitiv資料庫；公司財務數據與債券數據來自datastream資料庫，並使用PSM配對法排除自選擇偏差，得到實驗組(綠債)與對照組(一般債)共2組樣本，進行DID模型實證。而實證結果發現，綠債發行與企業的總排放、直接碳排與間接碳排放無顯著負相關。
另外，由於高碳排產業與非高碳排產業面臨的碳風險與資金成本不同，以及每間企業擁有不同的董事會性別比，可能將影響綠債發行後的減排效果，故本文嘗試找出影響碳排強度之因素，發現在綠債發行後，高碳排產業其碳排放的下降效果更顯著，但女性董事比例並未增強綠債發行與碳排放間的負相關性。

Due to the acceleration of global warming caused by greenhouse gas emissions, many countries have enacted agreements to reduce carbon emissions. To achieve carbon reduction targets, more and more enterprises are now using green bond as finance tools. As a result, the amount of green bond issuance has significantly increased in recent years, especially in the European Union, which is well developed in green bond market.
As an important green finance tools, whether the issuance of green bonds can reduce carbon emissions is a significant issue. To avoid biases caused by different regions and greenwashing, this paper selects the European Union region, which has strict green bond regulations. This study also includes direct and indirect carbon emissions to explore whether there are different results in diverse carbon intensity measures after the the issuance of green bonds.
The sample period of this study spans from 2018 to 2021, with all data sourced from Thomson Reuters and Datastream database. The PSM-DID matching method is used to exclude self-selection bias. The empirical results shows that the issuance of green bonds is not negatively correlated with three kinds of carbon intensity. Additionally, high carbon industries and board gender ratios are added to identify the factors influencing on carbon intensity. It is found after the issuance of green bonds, the carbon emissions reduction is more significant in high-carbon industries. However, the carbon emissions reduction is not significant in high proportion of female directors.

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