Global efforts to combat climate change in the last two decades have contributed to considerably cutting carbon emissions, according to a new study conducted primarily by scientists from Germany and the United Kingdom. The participating researchers investigated which climate policies were particularly effective. Reduced emissions have generally been the result of ambitious, i.e., larger and stricter climate policy portfolios. In addition, countries targeting the largest sources of emissions were particularly successful, according to the experts from Heidelberg University, who played a major role in the study.
The research findings are based on a statistical analysis of a comprehensive data set on climate policies implemented between 2000 and 2022 in the 43 largest economies worldwide, which are responsible for well over three-quarters of emissions worldwide. This analysis was accompanied by case studies for Brazil, China, Estonia, Indonesia, Israel, Mexico, the UK and the United States, mostly conducted at Heidelberg University’s Institute of Political Science. The calculations made by the international team of scientists show the tangible impact of global efforts to fight climate change. They indicate that existing climate policies saved three billion tons of CO 2 in 2022 alone. That roughly corresponds, the researchers say, to the annual emissions of the whole of the European Union.
For the study, the team at Heidelberg University, headed by political scientist Prof. Dr Jale Tosun, examined which specific policy instruments – that is, economic, regulatory or voluntary instruments – were used in individual states. “Here we followed up the question of whether broad-brush or, rather, specialized approaches were more successful in cutting emissions,” explains Dr Simon Bulian, an academic staff member in Prof. Tosun’s team. The results show that states focusing on an economic approach – for example, Estonia – or a regulatory approach – for example, Israel – were able to cut their emissions more effectively than states without such specializations. In addition, a key factor was targeting the leading sources of carbon emissions, in most cases energy generation and transport.
Independently of the focus adopted in terms of climate policy, economic instruments proved especially effective for cutting emissions, including, for example, a carbon tax or subsidizing renewable energies, Dr Bulian explains. According to the scientist, the study also points to a positive influence of international cooperation. Climate action tools were more effective in countries that – as a consequence of international climate conferences – had written long-term climate goals into law and hence pursued a stricter climate policy. Likewise, involvement in international organizations such as the International Energy Agency or the Clean Energy Ministerial has led to greater effectiveness of climate policy.
“Countries’ climate policy portfolios are growing – and they work, in spite of increasing political debates about whether they are necessary and efficient. Nevertheless, the emissions are still far too high to stop climate change or at least slow it down,” Prof. Tosun emphasizes. “The challenge for the future will be to implement policy instruments in an even more targeted and stringent way than has happened to date.” Participating in the study were scientists from Cardiff University, the University of Oxford, the University of East Anglia and the London School of Economics and Political Science, Heidelberg University and the International Institute for Applied Systems Analysis in Austria. The studies were largely funded by the European Union, the UK Economic and Social Research Council, and the Ministry of Economy, Trade and Industry of Japan. The research findings were published in “Nature Communications”.
Nature Communications
Climate policy portfolios that accelerate emission reductions
23-Jan-2026