HI Facts

“Believe/Don’t Believe” in Climate Change?”


Whatever your beliefs, here are the facts (and projections) about Hawaii’s changing climate:

Air Temperature

  • Remember 2015 and 2016? The warmest years on record. 2015 and 2016 were the warmest years ever, the world over and in Hawai‘i. It was so hot in Honolulu that emergency public service announcements were issued to curtail escalating air conditioning use that stressed the electrical grid. It was an El Niño year. Strong El Niño years in Hawai‘i bring more hot days, intense rains, windless days, active hurricane seasons, and spikes in sea surface temperature.
  • What’s coming? Some model projections for the late 21st century indicate that surface air temperature over land will increase 1.8° to 7.2°F (2° to 4°C). Frequency of intense El Niño is projected to double in the 21st century, with the likelihood of extreme events occurring roughly once every decade.

Wind and Precipitation

  • Hawai‘i is getting drier! Hawai‘i has seen an overall decline in rainfall over the past 30 years, with widely varying precipitation patterns on each island. The period since 2008 has been particularly dry. Stream flow in Hawai‘i has declined over approximately the past century, consistent with observed decreases in rainfall. This indicates declining groundwater levels and in-turn, the potential for drinking water shortages.
  • When we get rain, it is heavier. And that means more runoff, erosion, and flooding.
  • What’s coming? More frequent tropical cyclones are projected for the waters near Hawai‘i. This is not necessarily because there will be more storms forming in the east Pacific; but it is projected that storms will follow new tracks that bring them into the region of Hawai‘i more often.

Sea Level Change

  • Ongoing Local Sea Level Rise. The Honolulu tide gauge has measured a rise in sea level of nearly ½ foot since 1905.
  • Beach Erosion from Sea Level Rise is already happening. Over 70% of beaches in Hawai‘i are in a state of chronic erosion, likely caused by a combination of shoreline hardening and ongoing sea level rise.
  • More frequent high tide flooding. The frequency of high tide flooding in Honolulu since the 1960s, has increased from 6 days per year to 11 per year. High tide flooding is produced by wave over-wash and reverse flow through storm drains into basements and onto streets—you don’t have to live on the coast to see this kind of flooding.
  • Hawaiian cultural practices are affected. In Hawaiʻi, sea level rise impacts on traditional and customary practices (including fishpond maintenance, cultivation of salt, and gathering from the nearshore fisheries) have been observed. Because of flooding and sea level rise, indigenous practitioners have had limited access to the land where salt is traditionally cultivated and harvested since 2014. Detachment from traditional lands has a negative effect on people’s spiritual and mental health.
  • What’s coming? About 550 cultural sites, 38 miles of major roads, and more than $19 billion in assets will be vulnerable to chronic flooding resulting from a 3.2 ft increase in sea level. Such widespread flooding will change the character of the island by affecting cultural heritage and daily commerce/lifestyles.

The information on this page is adapted from: Climate Change Brief. 2018. City and County of Honolulu Climate Change Commission.