Measuring the Words vs. Deeds Gap: A Presentation of the Vertical Climate Policy Harmonization Index

Amongst the many challenges that hamper the ability of the global regime to effectively address climate change is the translation of countries’ international commitments to domestic policies. To facilitate the adoption of the Paris Agreement at the international stage and its successful implementation in the domestic arena, countries must harmonize their interests at the various levels of governance. However, this is a complex task that often results in a gap between what international negotiators promise and what domestic policymakers adopt. We present the novel Vertical Policy Harmonization Index (VPHI) that measures the difference between policy output at the international level, i.e., countries’ commitments to climate change mitigation as communicated in their Nationally Determined Contributions (NDCs), and their domestic strategies, plans or policies to implement those commitments. In this paper, we show the conceptualization and operationalization of this new index and discuss its validity and added value in contrast to other climate policy or performance indices. Finally, we draw on hypotheses from the climate governance literature and use regression analysis to study how various macro-level characteristics influence countries’ level of vertical policy harmonization. We expect that some macro-level factors (e.g., high vulnerability and low abatement costs) facilitate vertical policy harmonization, whereas others (e.g., many veto players in the domestic policy decision-making process) have a debilitating effect.