Indonesia Climate Change: Observations and Future Projections in IPCC AR6 WG I and Beyond

This study aimed to comprehensively review and synthesize results specific to the Indonesian archipelago from the IPCC Sixth Assessment Report (AR6) Working Group I, "The Physical Science Basis." At the heart of the Indo-Pacific maritime continent, Indonesia's climate was undergoing significant anthropogenic alteration owing to complex atmospheric and oceanic processes. The review distilled pertinent observations, trends, and projections, while also offering a detailed analysis of the underlying physical science. The observed changes included a significant rise in tropospheric ozone since the 1990s, a persistent trend towards a La Niña-like state in the Pacific Walker Circulation, accelerated warming of surrounding tropical oceans, and increased multi-decadal variability in the Indonesian Throughflow. The regional water cycle was also intensifying, marked by an increase in rainfall extremes which occurred against a background of powerful climate variability modes such as El Niño-Southern Oscillation and Indian Ocean Dipole, contributing to severe events such as the 2015-2016 drought and fire crisis. Future projections assessed with high confidence pointed towards a decrease in annual mean precipitation with particularly severe drying of up to 30% projected for the summer months over key islands. These multifaceted changes have profound implications for Indonesia's environmental stability, socioeconomic development, and population well-being, underscoring the critical urgency for science-informed, targeted climate adaptation and mitigation strategies.