What does climate change mean for Hawai’i?

Sitting in the Central Pacific, Hawaii is seriously threatened by climate change with higher temperatures, sea level rise, and inconsistent rainfall patterns.  

Hawaii is getting hotter and drier. In 2019, Oahu recorded its hottest year ever, and the last 5 years have seen peak average temperatures across all five main islands. The average temperatures have already increased 1-2° F over the past 50 years and it is predicted that the average temperatures could increase by as much as 5-7° F by the end of the century. Increased temperatures are also causing more extreme weather events across Hawaii like drought, heavy rainfall, and increased tropical storms. Although there is lower average rainfall across the islands, some parts of Hawaii are becoming too dry while other parts flood. Rainfall patterns have changed so that rain typically comes all at once (for example the 2018 “rain bomb” on Kauai), which is increasing landslides, runoff, algae blooms, erosion, and flooding. Since the 1960s, flooding across Hawaii has increased sharply and is expected to keep rising. Climate change will severely affect communities, ecosystems, and economies across Hawaii. 

Source: NOAA

Increasing atmospheric temperatures are also warming the oceans around Hawaii. Ocean temperatures have increased several degrees in the past century, damaging coral reefs and the organisms that depend on them. The algae that live inside corals and provide their food become damaged with the rising temperatures, ending the symbiotic relationship that keeps corals healthy. This is called coral bleaching and is the reason for many reefs around Hawaii losing color and dying. Under increased stress from higher ocean temperatures, corals are also more likely to get diseases. Warming oceans are also causing oceans to be more acidic, as carbon dioxide reacts with water to form carbonic acid. Ocean acidification is very worrying for corals, shellfish, and other creatures that depend on ocean minerals to produce their skeletons and shells. The acidity of the Pacific Ocean has increased by about 25 percent in the past 30 years, and is expected to increase by another 40 to 50 percent by 2100. Due to these factors, it is expected that 40% of Hawaii’s reef fish will lose their habitat by 2100.  

Sea level rise also seriously threatens Hawaii. With the ice caps melting at ever increasing rates, the sea level around Hawaii is rising 1 inch every 4 years. In Hilo Bay, the sea level has risen 10 inches since 1950. By 2100, it is expected that the global sea level will rise from anywhere between 0.5 and 3.2 feet. 

Source: Hawaiʻi Climate Change Mitigation and Adaptation Commission

This will have serious consequences for Hawaii as it will exacerbate chronic coastal erosion, impacts from seasonal high waves, coastal inundation due to storm surge and tsunami, and drainage problems due to the convergence of high tide and rainfall run-off. It is expected that Hawaii will experience more frequent high tide and inland flooding, coastal erosion, and a loss of traditional and cultural practices. Currently, 70% of Hawaii’s beaches are threatened by sea level rise and coastal erosion. More frequent flooding will overwhelm drainage systems and damage infrastructure and roads, seriously threatening communities across Hawaii, many of which rely on singular roads going in and out. In the future, chronic flooding is estimated to make an additional 25,800 acres of land unusable, risking 6,500 infrastructures, 38 miles of major roads, about 550 cultural sites, and at least $19 billion in assets.

Source: Hawaiʻi Climate Change Mitigation and Adaptation Commission. 2017. Hawaiʻi Sea Level Rise Vulnerability and Adaptation Report. Prepared by Tetra Tech, Inc. and the State of Hawaiʻi Department of Land and Natural Resources, Office of Conservation and Coastal Lands, under the State of Hawaiʻi Department of Land and Natural Resources Contract No: 64064