EU Carbon Trading System Emerges as Most Effective Tool to Reduce Emissions

A World Bank study finds that emissions trading systems can significantly reduce carbon emissions when designed with strict rules, declining caps, and broad sector coverage, with the EU-ETS emerging as the most successful example. However, weaker systems or those excluding major polluting sectors, such as agriculture in New Zealand, deliver far smaller climate benefits.

As countries struggle to meet climate targets, emissions trading systems (ETSs) have become one of the world's most widely used tools for cutting carbon emissions. These systems place a price on pollution by requiring industries to buy permits for the carbon they emit. Companies that reduce emissions can sell unused permits, while heavier polluters must pay more.

But an important question has remained unanswered for years: do carbon markets actually reduce emissions in the real world?

A new World Bank Policy Research Working Paper by independent researcher Ze Song, University of Illinois Urbana-Champaign professor Gal Hochman, and World Bank senior economist Govinda Timilsina provides strong evidence that emissions trading systems can work but only if they are designed properly and tightened over time.

The study examined the emissions trading systems of the European Union, New Zealand, and South Korea using data from 137 countries between 2000 and 2020.

Europe Shows the Strongest Results

Among all the systems studied, the European Union's ETS delivered the most consistent and significant emissions cuts.

Launched in 2005, the EU-ETS covers sectors including electricity generation, heavy industry, aviation, and maritime transport. According to the study, the system reduced electricity-sector carbon dioxide emissions by 21.3 percent between 2005 and 2020 compared with a scenario without the ETS. Overall, national emissions across EU countries fell by 15.6 percent during the same period.

The strongest results came from the EU-15 countries, the bloc's older and more industrialized members before the 2004 expansion. In these countries, electricity-sector emissions dropped by more than 30 percent.

Researchers say the EU system became more effective because Europe gradually tightened the rules. Over time, the EU reduced free permits, increased auctioning of allowances, and introduced stricter emissions caps. These reforms steadily raised the cost of pollution and pushed industries toward cleaner technologies and renewable energy.

The study suggests that strong regulation and declining emissions caps are essential for any successful carbon market.

New Zealand's Weak Spot: Agriculture

New Zealand's emissions trading system produced mixed results.

Introduced in 2008, the NZ-ETS reduced emissions in the electricity sector, but failed to lower emissions at the national level in a meaningful way. The main reason was agriculture.

Agriculture accounts for nearly half of New Zealand's greenhouse gas emissions, yet the sector was excluded from the ETS during the study period. As a result, even though emissions from energy-related sectors declined, the country's biggest source of pollution remained untouched.

The researchers estimate that electricity-sector emissions declined by around 1.3 million tons between 2008 and 2020, but overall national emissions continued to rise relative to the estimated counterfactual scenario.

The paper also notes that political changes after 2017 appeared to influence emissions trends, contributing to a reversal in some earlier reductions.

South Korea Needed Stronger Rules

South Korea's ETS followed a different path.

Launched in 2015, the Korean carbon market initially failed to reduce emissions. During its first phase, companies received large numbers of free permits, while extra allowances flooded the market. This weakened the financial pressure to cut emissions.

However, reforms introduced later made the system more effective. South Korea began auctioning some permits, tightened market conditions, and strengthened benchmarking rules that linked emissions performance more directly to compliance.

As these reforms took effect, emissions started to decline more noticeably in both the electricity sector and the wider economy.

The study concludes that South Korea's experience shows how weak carbon markets can gradually become effective if governments strengthen the rules over time.

The Bigger Lesson for Climate Policy

The study argues that emissions trading systems are neither automatic successes nor failures. Their effectiveness depends heavily on how they are designed.

Carbon markets work best when they include broad sector coverage, steadily declining emissions caps, limited free permits, and strong enforcement. Systems with weak pricing signals or major sectors left out tend to produce limited results.

The researchers also highlight a political challenge. Stronger carbon markets usually deliver better environmental outcomes, but they are often harder for governments to implement because industries fear higher costs and economic disruption.

Even so, the paper concludes that emissions trading systems remain one of the most important market-based tools available for reducing carbon emissions. The success of the European Union's system, in particular, shows that carbon pricing can drive long-term decarbonization when governments are willing to tighten policies gradually and consistently over time.