Climate games: how national climate vulnerability reframes decision-making scenarios on climate action

This thesis investigates how a country's individual level of climate vulnerability shapes its incentives to invest in combating climate change. Building on the prevalent view that international cooperation on dealing with climate change issues suffers from free-riding, I extend a formal game-theoretic model that embeds country-specific vulnerability directly on the payoff and the Nash equilibria. The model reframes “investment leadership” away from cost differentials alone and toward the benefit-cost relation (Bi / ki), showing that higher vulnerability raises the marginal benefit of investing, which shifts best responses and, in some cases, overturn free-riding equilibria even when absolute costs are high. To illustrate the theoretical game model, I present two real-world applications. One hard case where a country with high vulnerability takes the lead on investing, despite the high costs of it, and an upcoming case of a country with vulnerability-adjusted leadership in climate action. The findings bridge international externalities and domestic political economy, suggesting that rising climate vulnerability can strengthen incentives to invest over free-ride in decision-making scenarios.