This paper explores the intricate relationship between the climate crisis and classical liberalism, specifically through the lens of John Rawls' political philosophy. In the context of the climate crisis, we assess the applicability of Rawls' principles, with a particular focus on the so-called 'circumstances of justice.' Rawls' philosophy is not without its limitations, primarily due to its normative nature and anthropocentric perspective. Furthermore, the climate crisis doesn't neatly fit into what Rawls defines as 'the circumstances of justice'—the conditions from which principles of justice are derived. To address these challenges, we propose a post-human liberalism, a framework that broadens the concept of 'human' to include all members of the ecosystem. This approach advocates for global democracy and international cooperation, placing a strong emphasis on the fundamental principle of coexistence. In conclusion, this paper underscores the pressing need for posthuman liberalism in the face of the climate crisis. Such a philosophy would redefine the relationship between humans and nature, adopting a holistic ecosystem perspective and promoting the crucial value of coexistence as we strive to address this critical global challenge.