The 2012 Pacific Islands Regional Climate Assessment (PIRCA) identified several important indicators of climate change in the region, such as:
- Average surface air temperatures are rising, with the largest increases found at high altitudes in Hawai‘i.
- Over the past century, rainfall has decreased across much of the region. There has been a slight increase in rainfall in the westernmost Micronesian islands.
- In Hawai‘i, groundwater discharge to streams has significantly decreased over the past 100 years. This trend indicates a decrease in groundwater storage.
- Mean sea levels are rising, particularly in the Western Pacific.
- Across the region, the frequency and intensity of climatic extremes are changing. Drought has been more frequent and prolonged, and there have been fewer tropical cyclones.
- Pacific Island habitats and species distributions have changed. For example,
increasing temperatures are facilitating the upward migration of mosquito-borne
diseases that cause mortality in Hawaiian native forest birds.
- Ocean heat content is rising and ocean chemistry is changing.