Rising Temperatures


2019 was the hottest year ever recorded on O‘ahu, featuring the hottest day ever recorded in Honolulu’s history. The last five years have seen peak average annual temperatures years across all islands. Temperatures are increasing by 0.3°F every decade, at four times the rate of half a century ago. In 2015-2016, it was so hot in Honolulu that emergency public service announcements were issued to curtail escalating air conditioning use because it stressed the electrical grid. It was an El Niño (ENSO) year. Strong ENSO years bring more hot days, intense rains, windless days, active hurricane seasons, and spikes in sea surface temperature. ENSO events are naturally occurring, but their frequency and intensity are worsened by climate change since they are caused by warmer sea surface temperatures and weak winds. This creates a positive feedback loop of irregular weather patterns. The Hawaiʻi Climate Data Portal’s Climate Tool offers visualizations and historical data about temperature across the State.

Observed historical average annual temperatures in the islands of Kauaʻi, Oʻahu, Maui, and Hawaiʻi from 1950 to 2010. Photo was taken from NOAA State Climate Summaries.
Since the 1950's, temperatures in Hawai‘i have been consistently above the historical average and are continuing to increase, Photo by NOAA State Climate Summaries


HAWAIʻI HAS LOST 1.5 MILLION ACRES OF NATIVE FORESTS. Hawaii’s forests are natural water and climate regulators. Without them, we are seeing disruptions in weather and temperature patterns. In other words, climate change and forest loss are working together to make Hawai‘i drier and hotter.

INVASIVE SPECIES ARE WINNING THE WAR. Hotter summers make it easy for fast-growing invasive species like Californian shrubs and grasses to gain a foothold and outgrow our native tree species. On Maui, you may have noticed more grasslands where shady, wet forests used to be. These grasses and shrubs are not only outcompeting our beloved ʻōhiʻa, they are increasing the risk of wildfire. Warmer temperatures mean avian malaria can survive at higher elevations as well. 10 native species are projected to lose 50% of their mosquito-free range by 2100, with 3 species losing over 90%, and 3 species losing 100%.

INCREASING LOSS OF LAND AREA. Worsened by climate change, growing numbers of wildfires don’t just cost us our land. They harm our fragile ecosystems, spread disease, degrade air quality, cause landslides, and destroy valuable resources and infrastructure.  

WARMING WATERS ARE HARMING SEA LIFE. Warmer water means less oxygen in the water, making it hard for corals and beneficial algae to survive. In turn, the creatures that depend on them suffer as well. Our tourism and fishing industries depend on the health of these creatures because they represent food and shelter to our economically important fish species. Just think – how will tourism be affected if there are no colorful fish for snorkelers to see?

HIGHER TEMPERATURES THREATEN OUR INFRASTRUCTURE. Increases in sea surface temperatures cause irregular weather patterns like drought, heavy rainstorms, and intense tropical storms. Greater heat wave intensity, increased rates of soil moisture loss, and a doubling of days with a temperature over 90°F and nights over 75°F are straining our energy and water infrastructure.

A helicopter circles a wildfire in Kauaʻi, where these fires are becoming increasingly common during drier summer months. Photo by Brian Howell, Flickr Commons.
A helicopter circles a wildfire on Kaua‘i, where these fires are becoming increasingly common during drier summer months, Photo by Brian Howell, Flickr Commons


In Hawai‘i, average temperatures could increase by as much as 5 – 7.5° F by the end of the century. We can expect this to severely affect our communities, ecosystems, and economy. Hawaii’s coral reefs alone bring in $385 billion a year. 40% of our reefs could be lost by 2100 because of warming seas, which will affect tourism. The economic and public health risks of a changing climate will make certain people –children, the elderly, and economically disadvantaged– especially vulnerable. Hawai‘i must adapt to higher temperatures and work to mitigate their harmful effects for greater future security.