As sea-level rise poses an existential threat to low-lying Pacific island nations, the 2023 "Falepili Union" treaty between Australia and Tuvalu has emerged as a landmark "resettlement-for-security" model in global climate diplomacy. However, the sustainable implementation of such climate-induced migration policies depends heavily on the "social license" and acceptance within the host country. This research adopts an interdisciplinary approach, bridging International Relations’ "Human Security" framework with Geographic "Social Sensing" methodologies to evaluate Australian public sentiment toward this treaty.

By harvesting a longitudinal corpus from digital platforms including Reddit (r/australia, r/AustralianPolitics) and X (Twitter) since November 2023, this study utilizes Large Language Models (LLMs), specifically GPT-4o, to perform deep semantic mining and automated qualitative coding. Unlike traditional sentiment analysis, the LLM-driven pipeline identifies nuanced narrative frames, categorizing public discourse into dimensions of climate justice, national security, economic cost, and sovereign concerns.

Preliminary findings indicate a complex tension between humanitarian obligations and geopolitical skepticism. The research further explores the spatio-temporal evolution of these sentiments, mapping how digital discourse responds to specific policy milestones. This study contributes a novel computational framework for assessing the domestic legitimacy of climate migration policies, providing data-driven insights for policymakers to foster social cohesion in the face of escalating regional climate crises.