ABSTRACT

We assess evidence from theoretical-modelling, empirical and experimental studies on how interactions between instruments of climate policy affect overall emissions reduction. Such interactions take the form of negative, zero or positive synergistic effects. The considered instruments comprise performance and technical standards, carbon pricing, adoption subsidies, innovation support, and information provision. Based on the findings, we formulate climate-policy packages that avoid negative and employ positive synergies, and compare their strengths and weaknesses on other criteria. We note that the international context of climate policy has been neglected in assessments of policy mixes, and argue that transparency and harmonization of national policies may be key to a politically feasible path to meet global emission targets. This suggests limiting the complexity of climate-policy packages.

Key policy insights

• Combining technical standards or targets, such as renewable-energy quota, or adoption subsidies with a carbon market can produce negative synergy, up to the point of adding no emissions reduction beyond the cap. For maximum emissions reduction, renewable energy policy should be combined with carbon taxation and target expensive reduction options not triggered by the tax.

• Evidence regarding synergy of information provision with pricing is mixed, indicating a tendency for complementary roles (zero synergy). Positive synergy is documented only for cases where information provision improves effectiveness of price instruments, e.g. by stimulating social imitation of low-carbon choices.

• We conclude that the most promising packages are combining innovation support and information provision with either a carbon tax and adoption subsidy, or with a carbon market. We further argue that the latter could have stronger potential to harmonize international policy, which would allow to strengthen mitigation policy over time.

摘要

我们评估了关于气候政策工具之间的相互作用如何影响整体减排的理论建模、实证和实验研究的证据。这种相互作用采取负面、零或正面协同效应的形式。考虑的工具包括性能和技术标准、碳定价、采用补贴、创新支持和信息提供。根据调查结果，我们制定了避免负面影响并采用积极协同效应的气候政策一揽子计划，并根据其他标准比较了它们的优势和劣势。我们注意到在评估政策组合时忽略了气候政策的国际背景，并认为国家政策的透明度和协调性可能是实现全球排放目标的政治可行途径的关键。

关键政策见解

• 将技术标准或目标（如可再生能源配额）或采用补贴与碳市场相结合，可以产生负协同作用，直至超出限额不增加任何减排量。为了最大限度地减少排放，可再生能源政策应与碳税相结合，并针对非碳税引发的昂贵减排选择。

• 关于信息提供与定价协同作用的证据是混合的，表明存在互补作用（零协同作用）的趋势。只有在信息提供提高价格工具有效性的情况下才会记录到积极的协同作用，例如通过刺激低碳选择的社会模仿。

• 我们得出的结论是，最有前途的一揽子计划是将创新支持和信息提供与碳税和收养补贴或碳市场相结合。我们进一步认为，后者可能具有更大的协调国际政策的潜力，这将允许随着时间的推移加强缓解政策。