This study investigates instruments that could generate revenue for international climate finance. Through a mixed-methods approach, including desk research and interviews with 23 experts from diverse professional backgrounds, the study evaluates four proposed levies: a Fossil Fuel Extraction Levy, a Levy on Windfall Fossil Fuel Profits, a Levy on Plastic Polymers, and a Levy on Jet Fuel. 

Each instrument is assessed in terms of its political and technical feasibility and revenue potential. Key findings suggest that while global implementation could yield significant revenue, plurilateral approaches led by coalitions of willing countries may be quicker to implement and more ambitious than near-global agreements. Legal and political challenges, particularly in securing relevant parties’ participation, ensuring the earmarking of funds for (international) climate financing purposes, and fiscal stabilisation clauses that could hinder the implementation of new levies especially in developing and emerging economies are highlighted as major hurdles. 

The study recommends gradual implementation and the strategic use of revenues to garner broader acceptance. While the four assessed instruments all have the potential to generate significant revenue streams for climate finance, no instrument emerges as an obvious "best-choice".