The failure of climate policies

An analysis of 15,000 climate policies reveals that only a small fraction achieved significant emissions reductions.

A new analysis using machine learning (a type of artificial intelligence) has revealed which are the most effective climate policies among 15,000 implemented around the world over the past two decades.

Some of the success stories, which number only about six dozen, involve rarely studied policies and under-appreciated policy combinations.

“Our results offer a clear but sobering perspective on the policy effort needed to close the remaining 23 billion tonne carbon dioxide (CO2) emissions gap by 2023,” the authors explain.

To achieve the climate goals of the Paris Agreement, it is essential to know which climate policies work effectively at scale. However, despite the implementation of thousands of climate policies around the world over the past two decades, there has been little consensus on which ones are the most effective.

This underlines the need for a detailed global assessment.

The evaluation carried out on this occasion by Annika Stechemesser’s team from the Potsdam Institute for Climate Impact Research in Germany offers revealing perspectives based on the aforementioned evaluation of 15,000 climate policies, which were implemented in 41 countries between 1998 and 2022.

Analysis of 15,000 climate policies reveals that only a small fraction achieved significant emissions reductions. (Illustration: NASA JPL/Caltech)

The study’s authors used data from the Organisation for Economic Co-operation and Development (OECD) Climate Policy Database. They also used a machine learning-based extension of the standard differences-in-differences (DID) approach, a statistical technique used to estimate the causal effect of an intervention (such as a climate policy) by comparing changes in outcomes over time between a group exposed to the intervention and a group not exposed.

Stechemesser and his colleagues assessed the impact of each policy on emissions across different regions and time periods.

Of the 15,000 climate policies, the study’s authors identified only 63 policy interventions that reduced total emissions by between 600 and 1.8 billion tonnes of CO2.

Judging by the findings of the new study, combining several policy instruments is often more effective than using individual measures, contradicting claims that policy mixes might be redundant. Effective policies typically involve a mix of subsidies and regulations that address different market failures. Price mechanisms are prominent in the industry and electricity sectors, while a mix of incentives and regulations benefits the buildings and transport sectors. In developing countries, price mechanisms were less effective, indicating that initial regulatory and subsidy measures might be necessary. While scaling up successful policies could close the emissions gap, it will require significant additional effort, including the need for more research and improved data.

The study is titled “Climate policies that achieved major emission reductions: Global evidence from two decades.” It has been published in the academic journal Science. (Source: AAAS)