A	United States
Environmental Protection
LI M % Agency
What Climate Change
Means for Hawaii
Hawaii's climate is changing. In the last century, air
temperatures have increased between one-half and one
degree (F). Warming in the oceans around Hawaii has
damaged coral reefs, and, in recent decades, increased
ocean acidity has threatened reefs and other marine
ecosystems. Average precipitation decreased in the last
century, reducing freshwater availability on some islands and
affecting delicate land-based ecosystems, often harming
native species. In the last 50 years, sea level has risen along
Hawaii's shores, increasing erosion and threatening coastal
communities and infrastructure.
Climate is changing because the earth is warming. People
have increased the amount of carbon dioxide in the air by
40 percent since the late 1700s. Other heat-trapping green-
house gases are also increasing. These gases have warmed
the surface and lower atmosphere of our planet about one
degree during the last 50 years. Evaporation increases as
the atmosphere warms, which increases humidity, average
rainfall, and the frequency of heavy rainstorms in many
places—but contributes to drought in others.
Greenhouse gases are also changing the world's oceans and
ice cover. Carbon dioxide reacts with water to form carbonic
acid, so the oceans are becoming more acidic. The surface
of the ocean has warmed about one degree during the last
80 years. Warming is causing snow to melt earlier in spring,
and mountain glaciers are retreating. Even the great ice
sheets on Greenland and Antarctica are shrinking. Thus the
sea is rising at an increasing rate.
Honuuu —Kahuui
- Hilo
1980 1990
Average annual temperatures have increased across Hawaii since
1950. Source: NOAA
Ocean Warming and AcidiBbation
The waters around Hawaii are warming, which is harming
Hawaii's coral reefs and marine ecosystems. The El Nino-
Southern Oscillation ("El Nino") and other natural cycles cause
ocean temperatures in the Pacific to fluctuate from year to year
and from decade to decade. Even after accounting for these
natural patterns, the waters around Hawaii have been warming
since the 1950s, with temperatures rising by several degrees
from the ocean surface down to at least 600 feet. Rising water
temperatures can harm the algae that live inside corals. Because
algae provide food for the coral, a loss of algae weakens corals
and can eventually kill them. This process is commonly known as
"coral bleaching," because the loss of the algae also causes the
corals to turn white. Mass bleaching events are becoming more
common, with documented cases in the north-western Hawaiian
Islands in 1996 and 2002. Water temperature spikes in Hawaii
have also been linked to coral disease outbreaks.
Bleached corals in Kaneohe Bay, Oahu, in the fall of 2014, Credit: XL
Catlin Seaview Survey
Increasing ocean acidity can also damage corals, as well as
shellfish and other organisms that depend on minerals in the
water to build their skeletons and shells. The acidity of the
Pacific Ocean has increased by about 25 percent in the past
three centuries, and it is likely to increase another 40 to 50
percent by 2100.
Warming and acidification could result in widespread damage to
the entire marine ecosystem in the waters off Hawaii. Hawaii's
isolation in the Central Pacific makes it home to a wide range of
fish species not found anywhere else in the world. Many of these
fish rely on healthy coral reefs for habitat, and even with substan-
tial cuts to greenhouse gas emissions, up to 40 percent of coral

Tourism infrastructure and nearshore coral reefs, both threatened by
climate change, in Maui, Credit: Hudson Slay, EPA Region 9.
reef fish could lose their habitats by 2100. Reefs also protect
nearshore fish nurseries and feeding grounds. Damage to coral
and reduced fish populations could negatively impact the
state's economy, as these natural resources bring an estimated
$385 million to Hawaii each year through tourism, direct
consumption, and commercial fisheries.
Water Availability
Rainfall in Hawaii has been decreasing, but scientists do not
know whether that trend will continue. El Nino will probably
continue to dominate precipitation patterns from year to year in
the tropical Pacific. Climate change-related increases in air
temperatures will lead to more evaporation and more moisture
in the air. As a result, the variability in El Nino-related
precipitation is likely to increase, making rainfall predictions
Although projections of future rainfall are uncertain, streams and
rivers on the Hawaiian Islands have experienced a reduction in
flow over the last century, resulting in less fresh water available
for people and ecosystems. Additionally, increased drought may
threaten taro and breadfruit, which are important traditional food
sources for Hawaii's native peoples.
Land Ecosystem Changes
Ecosystems on land are also experiencing impacts from a
warming climate. Many native plant species could lose ground
to invasive species better adapted to the changing climate,
or simply fail to thrive in altered habitats. For example, higher
temperatures and increased drought have caused dramatic
declines among native plant species such as Haleakala silver-
sword. Some native species display the ability to adapt to climate
change, such as a few types of fire-adapted grasses that have
shifted to higher altitudes in Hawaii Volcanoes National Park.
However, some insects such as mosquitoes have also been able
to expand their ranges into higher elevations, infecting native
birds with diseases like avian malaria.
Shoreline Loss
Since 1960, sea level has risen between two and eight inches
relative to Hawaii's shoreline. Sea level rise can make Hawaii's
existing coastal hazards—such as waves, hurricanes, tsunamis,
and extreme tides—even worse. Additionally, rising sea level has
accelerated coastal erosion, which has resulted in wetland mi-
gration and cliff collapse. Chronic erosion has affected more than
70 percent of Kauai and Maui's beaches over the last century.
Sea level rise and the associated coastal impacts due to in-
creased flooding, elevated ground water tables, storm surge,
and erosion have the potential to harm an array of natural
and built environments in Hawaii, Dying coral reefs add to this
problem, as they leave the shoreline more vulnerable to erosion
and damage from waves. In the Northwestern Hawaiian Islands
Marine National Monument, sea level rise threatens native
species, especially those that nest on beaches, such as green
sea turtles, Hawaiian monk seals, and the endangered Laysan
finch. Damage to coastal infrastructure may also hurt Hawaii's
economy, more than a quarter of which stems from tourism.
WaiklkT Beach alone brings in $2 billion per year in visitor spend-
ing. Furthermore, many of Hawaii's native communities are in
vulnerable coastal areas. Sea level rise and associated flooding
are expected to destroy land, coastal artifacts, and structures of
significant cultural value, and may force these communities to
A seawall built in Ukumehame, Maui, to protect the shoreline and
coastal infrastructure from erosion. Credit: Hudson Slay, EPA Region 9.
Health and Vulnerable People
Climate change is likely to amplify some threats to health in Ha-
waii. Certain people are especially vulnerable, including children,
the elderly, the sick, and the poor.
The sources of information about ciimate and the impacts of climate change in this publication are: the national climate assessments by the U.S. Global Change
Research Program, synthesis and assessment products by the U.S. Climate Change Science Program, assessment reports by the Intergovernmental Panel on Climate
Change, and EPA's Climate Change Indicators in the United States. Mention of a particular season, location, species, or any other aspect of an impact does not imply
anything about the likelihood or importance of aspects that are not mentioned. For more Information about climate change science, Impacts, responses, and what you
can do, visit EPA's Climate Change website at www.epa.aov/climatechanae.