Climate Change in the Pacific Region
Pacific Region

Climate Change in the Pacific Islands

Coral reefs are at risk from rising temperatures, ocean acidification, and sea level rise. Coral garden, Palmyra Atoll NWR, by J. Maragos/USFWS

On This Page

Climate Change Overview
Changes in ENSO and Ocean Circulation Patterns
The Availability of Freshwater
Sea Level Rise
Coastal Inundation
Ocean Acidification
Coral Reefs
Effects in Hawai`i
Pacific Islands Climate Change Cooperative


In the Pacific Islands, we are collaborating with the Hawai`i Conservation Alliance and climate researchers at the University of Hawai`i’s International Pacific Research Center, the Department of Geography and many other Departments, NOAA, USGS, and many others. These collaborations are aimed at assessing historic climate trends and promoting the development of regional climate models that will aid in estimating future climate conditions in the Pacific Islands.

Conserving native species and ecosystems is a challenging task that is destined to become progressively more difficult as global climate change accelerates in the coming years. Temperature, rainfall patterns, sea level and ocean chemistry, to name but a few, will move beyond the range of our experience, and planning effective conservation will increasingly depend on predictive models and assessments rather than knowledge and data from the past.

To meet these challenges, the U.S. Fish and Wildlife Service is making a significant commitment of personnel and funding starting in 2010 to establish cooperative centers for conservation planning, or Landscape Conservation Cooperatives (LCCs). This is part of a national initiative by the Fish and Wildlife Service to bring climate change science to bear on natural resource management. Efforts will occur in collaboration with members of the Hawai`i Conservation Alliance.

The 17th annual Hawai‘i Conservation Conference attracted over 1,100 people in July, 2009, with its various lectures, symposia, and other presentations focusing on the theme “Hawai‘i in a Changing Climate.”

You can view over 84 of these presentations on the web, covering a range of conservation issues from climate change to invasive species to environmental education efforts throughout the Hawaiian archipelago. To view the presentations by session, visit the Hawai‘i Conservation Alliance (HCA) web site at or go directly to and browse the episodes. (The Fish and Wildlife Service is an HCA member.)

The following information is excerpted or summarized from the references cited.

Climate Change Overview

Climate change presents Pacific Islands with unique challenges including rising temperatures, sea-level rise, contamination of freshwater resources with saltwater, coastal erosion, an increase in extreme weather events, coral reef bleaching, and ocean acidification. Projections for the rest of this century suggest continued increases in air and ocean surface temperatures in the Pacific, increased frequency of extreme weather events, and increased rainfall during the summer months and a decrease in rainfall during the winter months.

In Hawai’i, annual rainfall has decreased and surface temperatures have risen during the last several decades, but it is unknown whether these trends will persist or change with global climate change. Coastal areas will be at increased risk due to greater hurricane wind speeds and coastal inundation due to the combined effects of sea-level rise and storm surges.

This graph is excerpted from United Global States Research Program, 2009

Changes in ENSO and Ocean Circulation Patterns

El Niño-Southern Oscillation (ENSO), resulting from the large-scale global interaction of atmospheric and oceanic circulation, is an inter-annual climatic phenomenon (approximately 3-8 years) that creates temperature fluctuations in the tropical surface waters of the Pacific Ocean. ENSO events can have a significant impact on ecosystems due to changing surface winds, ocean currents, water temperatures, ocean nutrient availability, storm frequency and magnitude, etc. ENSO is a naturally occurring phenomenon, but there is uncertainty regarding how global warming and the associated climate changes will impact the frequency, magnitude, and the duration of this cycle and how that will in turn affect ecosystems. For example, changes to established ocean circulation patterns can have significant effects on biological connectivity for marine organisms, the distribution of species, biological productivity, and marine debris issues. Changes in storm events can impact corals directly from wave damage or more indirectly from runoff and sediment deposition. (Baker and Smith, 2008)

The Availability of Freshwater

Most island communities in the Pacific have limited sources of freshwater. Many islands depend on freshwater lenses below the surface, which are recharged by precipitation. Changes in precipitation, such as the decreases currently observed in Hawai’i, are thus a cause of great concern. Sea-level rise also affects islands’ water supplies by causing saltwater to contaminate the freshwater lens and by causing an increased frequency of flooding during storm high tides. (United Global States Research Program, 2009)

Sea Level Rise

The melting of mountain glaciers and the Greenland and Antarctic ice sheets along with the thermal expansion of the oceans will likely continue to increase sea level for many hundreds of years into the future. The consensus estimate of sea level rise by 2100, published in the Intergovernmental Panel on Climate Change’s Fourth Assessment, was estimated at 0.6 to 2.0 ft. Improved estimates of the range of sea level rise by 2100, which now include estimated effects of ice dynamics, lie between 2.6 and 6.6 ft, a significantly higher estimate. (Pfeffer, W.T., et al., 2008)

As a result of sea level rise, low lying coastal areas will eventually be inundated by seawater or periodically over-washed by waves and storm surges. Coastal wetlands will become increasingly brackish as seawater inundates freshwater wetlands. New brackish and freshwater wetland areas will be created as seawater inundates low lying inland areas or as the freshwater table is pushed upward by the higher stand of seawater.

In the Pacific Islands there are many low lying atolls, including many that are part of the National Wildlife Refuge System. These atolls are home to an estimated 10 million breeding-aged sea birds, and many marine mammals, sea turtles, coral reef communities and other fish and wildlife.

Coastal Inundation

Flooding will become more frequent and coastal land will be permanently lost as the sea inundates low-lying areas and as shorelines erode. Loss of land will affect living things in coastal ecosystems. For example, the Northwestern Hawaiian Islands, which are low-lying and therefore at great risk from rising sea level, have a high concentration of threatened and endangered species, some of which exist nowhere else. With further warming, hurricane and typhoon peak wind intensities and rainfall are likely to increase, which, combined with sea-level rise, would cause higher storm surge levels. (United Global States Research Program, 2009)

Ocean Acidification

The ocean will eventually absorb most carbon dioxide released into the atmosphere as a result of the burning of fossil fuels. Dissolving of carbon dioxide into ocean surface waters will increase the acidity of ocean surface waters. Oceanic absorption of CO2 from fossil fuels may result in larger acidification changes over the next several centuries than any inferred from the geological record of the past 300 million years (with the possible exception of those resulting from rare, extreme events such as meteor impacts).

Virtually every major biological function has been shown to respond to acidification changes in seawater, including photosynthesis, respiration rate, growth rates, calcification rates, reproduction, and recruitment. Much of the attention has focused on carbonate-based animals and plants which form the foundation of our marine ecosystems. An increase in ocean acidity is likely to result in a decline in the ability of coral reefs to maintain their calcium carbonate structure. Phytoplankton that utilize calcium carbonate are also likely to decline in abundance, along with other carbonate-dependent animals such as marine snails and carbonate-dependent plants such as red marine algae.
(Smith and Baker, 2008, and Ocean Carbon and Biogeochemistry Program, 2008).

Coral Reefs

Emperor angelfish and hump corelHawai`i supports more than 70% of the coral reefs in the United States with additional extensive coral reefs in the Mariana Islands, American Samoa, and National Wildlife Refuge islands and atolls throughout the Pacific. Coral reefs are particularly sensitive to the impacts of climate change as even small increases in water temperature can cause coral bleaching. Rising sea surface temperature will place many coral reefs into a temperature category that may be marginal for corals and reef ecosystems, including much of the Indo-Pacific center of reef biodiversity. Ocean acidification due to rising carbon dioxide levels poses an additional threat to coral reefs and the rich ecosystems they support. At the current rate of increase, atmospheric CO2 concentrations will reduce the saturation state of carbonate minerals in the surface ocean over the next 70 years until nearly all the locations of coral reefs are at or beyond their normal environmental limits. This implies the widespread loss of coral reefs worldwide if carbon dioxide emissions continue unabated.

Coral bleaching and subsequent mortality can lead to habitat phase shifts where corals are replaced by algae. Although recent research has documented algal-dominated areas to occur naturally on many healthy Pacific reef systems, algal overgrowth, as the result of climate change, is indicative of decreased ecosystem health. (Guinotte et. al, 2003)

Effects in Hawai`i

In Hawai‘i, the seasonal and geographic distribution of rainfall and temperature has combined with steep, mountainous terrain to produce a wide array of island-scale climate regimes. These varying regimes in turn have supported the diversification of Hawai‘i native plants and animals. Increasing amounts of human-caused greenhouse gases will likely alter the archipelago’s terrestrial and marine environments by raising air and sea surface temperatures, changing the amount and distribution of precipitation, raising sea level, increasing ocean acidification, and exacerbating severe weather events.

Hawai‘ian climate has two main seasons: Ka‘u wela, the dry high sun season from May through October with warm, steady trade winds ; and Ho‘oilo, the cooler, wet season from November through April, with weaker and less frequent trade winds, and storms that bring rain across the islands. The atmospheric processes of these seasons are (1) the Hadley Cell climate that drives the trade winds and trade wind inversion, and (2) non-Hadley Cell climate that drives winter weather events such as Kona storms, the southern tails of mid-latitude cyclonic storms, and upper level atmospheric troughs. Other important climate features that affect Hawai‘i include El Niño drought events, hurricanes, and smaller scale weather processes.

Watch a video on Developing a Strategy to Address the Effects of Global Warming on Hawaii's Native Species by Stephen E. Miller, Science Advisor, U.S. Fish and Wildlife Service, Pacific Islands Office, Honolulu, HI. (July 30, 2008, 2008 Hawai'i Conservation Conference, Honolulu, HI.) Link to video (39 min-- please be patient while video loads)

Effects of Climate Change on Temperature in Hawai‘i: Overall, the daily temperature range in Hawai‘i is decreasing, resulting in a warmer environment, especially at higher elevations and at night. The average ambient temperature (at sea level) is projected to increase by about 4.1 (2.7 to 6.7)oF by 2100 (IPCC, 2007). These changes would increase the monthly average temperature to between 77oF to 86oF. Historically, temperature has been rising over the last 100 years with the greatest increase after 1975 (Giambelluca et al., 2008). The rate of increase at low elevation (0.16 oF per decade) is below the observed global temperature rise of 0.32oF per decade (IPCC, 2007). However, at high elevations, the rate of increase (0.48oF per decade) greatly exceeds the global rate.

Effects of Climate Change on Precipitation in Hawai‘i:
In the oceans around Hawai‘i, the average annual rainfall at sea level is about 25 inches. The orographic (mountain) features of the islands increase this annual average to about 70 inches but can exceed 240 inches in the wettest mountain areas. Rainfall is distributed unevenly across each high island, and rainfall gradients are extreme (approximately 25 inches per mile), creating very dry and wet areas. Global climate modeling predicts that net precipitation at sea level near the Hawaiian Islands will decrease in winter by about 4-6%, with no significant change during summer (IPCC AR4, 2007). Downscaling of global climate models indicate that wet-season (winter) precipitation will decrease by 5% to 10%, while dry-season (summer) precipitation will increase by about 5% (Timm and Diaz, 2009). Data on precipitation in Hawai‘i, which includes sea level precipitation and the added orographic effects, shows a steady and significant decline of about 15% over the last 15 to 20 years (Diaz et al., 2005; Chu and Chen, 2005). These data are also supported by a steady decline in stream flow beginning in the early 1940s (Oki, 2004).

Ae‘o or Hawaiian stiltEffects of Climate Change on Sea Level
Melting of grounded ice and thermal expansion of the oceans are expected to continue for many hundreds of years with a predicted rise of two to three feet this century (IPCC, 2007). Low-lying coastal areas will be periodically or permanently inundated by seawater, and salt water intrusion will permanently alter low coastal wetlands and low-lying freshwater resources (Fetcher, 2009). Sea level rise also is directly implicated in increasing frequency and severity of high wave inundation and accelerate beach erosion (Fetcher, 2009), which will impact coastal habitats (e.g., nesting areas), ports, and coastal infrastructure (e.g., roads, sewers, communities)


Extreme Sea-level Days: Honolulu, Hawaii
This graph is excerpted fromUnited Global States Research Program, 2009

Effects of Climate Change on Ocean Temperature
Nihoa IslandBy 2100 the monthly average sea surface temperature in Hawaiian waters may increase from 73 oF to between 75oF and 79oF (Vecchi and Soden, 2007). Bleaching of coral can be induced by long-term exposure (i.e. several weeks) to temperature increases of 1.8oF to 3.6oF . Localized and large scale coral bleaching have been observed in Hawai`i (1986 -1988, 1996, 2002) during periods of high sea surface temperatures (Jokiel and Coles, 1990; Jokiel and Brown, 2004). A continuation of the warming trend in Hawaii would lead to mass bleaching similar to those observed recently in other geographic locations.

Ocean Acidity and the Effects of Increased Carbon Dioxide
Human-caused carbon dioxide also dissolves into the oceans and acidifies the surface waters. Models of ocean acidification predict that by 2070, conditions around Hawai‘i will be marginal for corals, with even less favorable conditions in equatorial and western Pacific areas (Kleypas et al., 1999; Guinotte et al., 2003; Raven et al., 2005; Caldeira, 2007; Hoegh-Guldberg et al., 2007). Acidification has been observed to have a profound impact on Hawai‘ian coral and crustose coralline algae, reducing growth and calcification by as much as 20% (Jokiel et al. 2008). Acidification will inhibit, and eventually end, the growth of biota that rely on calcium carbonate structures (e.g., coral reefs, plankton, and mollusks) and so disrupt the marine food web.

Effects to Hawai`i’s Biodiversity
Hawai`i is situated in an area of the Pacific that is protected from the effects of major annual tropical storms while simultaneously receiving an abundant supply of annual rainfall and moderate year round temperatures. Annual rainfall has decreased and surface temperatures have risen during the last several decades, but it is unknown whether these trends will persist or change with global climate change. The seasonal pattern of Hawai`i’s rainfall combines with geographic and elevational features (up to 13,400 feet) to produce extreme rainfall gradients over short distances. These unique island features produce a wide range of ecological communities that have supported the diversification of Hawaiian plants and animals.

Hawai`i’s species are unique and highly vulnerable due to natural conditions of relatively small population sizes and ranges. These natural conditions have been affected by human activities with climate change impacts being the most recent and significant. It is likely that climate change will be felt very quickly and may lead to further declines and extinctions of the 400 listed Hawaiian species if conservation strategies are not quickly adjusted to meet the changes expected from climate and bioclimate modeling.

Hawai`i is affected by numerous climate change issues including: sea level rise, ocean acidification, changes in tropical storm severity and intensity, changes in ocean and air temperatures, changes in amount and distribution of precipitation, the interaction of climate change and invasive species, and a magnification of fire acting as a major modifier of ecosystem structure and integrity.

Climate change is already showing its effects in Hawai`i. Long-term temperature is rising and at higher elevations the rate is much higher than the global average rate Giambelluca et al., 2009). These higher elevation areas support the best remaining native ecosystems in Hawai’i. Precipitation is showing long term decreases and these decreases are expected to greatly affect drier leeward areas (Diaz et al. 2005; Chu and Chen 2005; Oki, 2004; Timm and Diaz 2009) that support the greatest amount of native biodiversity.Sea surface temperatures are steadily rising, which has lead to at least 5 recorded episodes of coral bleaching (Jokiel andColes 1990; Jokiel and Brown 2004). Sea level rise will likely exceed 1 meter by the end of the century Hawaii creeper(Fletcher 2009). The low-islands (less than 40 feet above sea level) of Hawai`i and the tropical Pacific support most of plant, bird, and invertebrate communities that are highly vulnerable to sea level rise and accompanying storm damage. The reduction in nesting and pupping beaches in the Northeastern Hawaiian Island for the Hawaiian monk seal and green sea turtle are also of primary concern.

Avian Malaria Parasite and native Hawaiian birds: Climate change threatens to greatly expand the range and viability of avian malaria at higher elevations. Currently, at higher elevations, the transmission of avian malaria and the development of the malaria parasite are seasonal, both occurring during the warm summer and fall The cooler winter months are critical to the survival of Honeycreepers, when avian malaria development in suppressed by low temperatures.As global warming elevates air temperatures, seasonal, high-elevation avian malaria-free areas will shrink and eventually disappear entirely (Benning et al. 2002; Atkinson and LaPointe 2009). The spread of mosquitoes and avian malaria into the high elevations may eventually lead to the extinction of many, perhaps all, of the Honeycreepers that currently survive in these malaria-free areas.

Pacific Islands Climate Change Cooperative

This LCC includes Hawai’i, the northwest Hawaiian Islands, and other Pacific Islands within the United States' jurisdiction. The Pacific Islands Climate Change Cooperative (PICCC) is sponsored and partly supported by the USFWS and hosted by the Hawai`i Conservation Alliance (HCA). The PICCC steering committee is comprised of HCA members and other partners, forming a cooperative partnership of Federal, State, private, Hawaiian, and non-governmental conservation organizations and academic institutions. The goal of the partnership is to develop and maintain a strategic conservation response to the ecological changes induced by climate change. This can best be accomplished by collaboratively sharing expertise, knowledge, and resources.

Cooperative members include: the Office of Hawaiian Affairs, the Hawaii Department of Natural Resources, the University of Hawaii, National Oceanic and Atmospheric Administration, National Park Service, Natural Resources Conservation Service, U.S. Forest Service, The Nature Conservancy, the U.S. Geological Survey, U.S. Army and Kamehameha Schools.

Learn more about the Cooperative with this fact sheet (PDF 212 KB),or contact Deanna Spooner, PICCC Coordinator, at or (808) 687-6175.


Atkinson, C.T. and D.A. LaPointe. 2009. Introduced avian diseases, climate change, and the future of Hawaiian Honeycreepers. J. Avian Medicine and Surgery Vol. 23: in press.

Benning, T.L., D. LaPointe, C.T. Atkinson and P.M. Vitousek. 2002. Interactions of climate change with biological invasions and land use in the Hawaiian Islands: modeling the fate of endemic birds using a geographic information system. Proc. National Academy of Sciences 99: 14246-14249

Caldeira, Ken. 2007. What corals are dying to tell us about CO2 and ocean acidification. Oceanography. Vol. 20:188-195.

Chu, P.S. and H. Chen. 2005. Interannual and interdecadal rainfall variations in the Hawaiian Islands. Journal of Climate. Vol.18:4796-4813.

Diaz, Henry F., Pao-Shin Chu, and Jon K. Eischeid. 2005. Rainfall changes in Hawai`i during the last century. 16th Conference on Climate Variability and Change, American Meteorological Society, Boston, MA.

Fletcher, Charles. 2009. How high is sea level likely to rise by the end of the 21st century? A Review of Research. In press at Shore and Beach.

Giambelluca, T. W., H. F. Diaz, and M. S. A. Luke. 2008. Secular temperature changes in Hawai‘i, Geophys. Res. Lett., 35, L12702, doi:10.1029/2008GL034377.

Guinotte, J.M., Buddemeier, R.W., Kleypas, J.A., October 2003. Future Coral Reef Habitat Marginality: Temporal and Spatial Effects of Climate Change in the PacificBasin. Coral Reefs (2003) 22: 551–558.

Hoegh-Guldberg, O., P. J. Mumby, A. J. Hooten, R. S. Steneck, P. Greenfield, E. Gomez, C. D. Harvell, P. F. Sale, A. J. Edwards, K. Caldeira, N. Knowlton, C. M. Eakin, R. Iglesias-Prieto, N. Muthiga, R. H. Bradbury, A. Dubi, M. E. Hatziolos. 2007. Coral reefs under rapid climate change and ocean acidification. Science. Vol 318: 1737-1742.

Jokiel, P.L. and S.L.Coles. 1990. Response of Hawaiian and other Indo-Pacific reef corals to elevated temperature. Coral Reefs. Vol 8:1155-162.

Jokiel, Paul and Eric Brown. 2004. Global warming, regional trends and inshore environmental conditions influence coral bleaching in Hawai`i. Global Change Biology. Vol 10: 1627–1641.

Jokiel, P.L., K. S. Rodgers, I. B. Kuffner, A. J. Andersson, E. F. Cox, F. T. Mackenzie. 2008. Ocean acidification and calcifying reef organisms: a mesocosm investigation. Coral Reefs (2008) 27:473–483.

Kleypas, Joan A., Robert W. Buddemeier, David Archer, Jean-Pierre Gattuso, Chris Langdon, and Bradley N. Opdyke. 1999. Geochemical Consequences of Increased Atmospheric Carbon Dioxide on Coral Reefs. Science. Vol 284: 118-120.

Ocean Carbon and Biogeochemistry Program, Subcommittee on Ocean Acidification. December 2, 2008. Ocean Acidification- Recommended Strategy for a U.S. National Research Program.

Oki, D.S. 2004. Trends in Streamflow Characteristics at Long-Term Gaging Stations, Hawaii: U.S. Geological Survey Scientific Investigations Report 2004-5080, 120 p.

Pao-Shin Chu AND Huaiqun Chen. 2005. Interannual and Interdecadal Rainfall Variations in the Hawaiian Islands. Journal of Climate. Vol. 18: 4796-4813.

Pfeffer, W.T., et al. September 5, 2008. Kinematic Constraints on Glacier Contributions to 21st- Century Sea- Level Rise, Science, 321.

Raven, John. Ken Caldeira, Harry Elderfield, Ove Hoegh-Guldberg, Peter Liss, Ulf Riebesell Leibniz, John Shepherd, Carol Turley and , Andrew Watson. 2005. Ocean acidification due to increasing atmospheric carbon dioxide. The Royal Society of London. ISBN 0 85403 617 2 This report can be found at

Smith, Ellen and Baker, Jason. Pacific Island Ecosystem Complex, from Osgood, K. E. (editor). August 2008. Climate Impacts on U.S. Living Marine Resources: National Marine Fisheries Service Concerns, Activities and Needs, U.S. Dep. Commerce, NOAA Tech. Memo. NMFS-F/SPO-89, 118 p.

Timm, Oliver and Henry F. Diaz. 2009. Synoptic-statistical approach to regional downscaling of IPCC twenty-first century climate projections: seasonal rainfall over the Hawaiian Islands. Journal of Climate. Vol. 22:4261-4280.

United Global Change Research Program. May 2009.

Vecchi, Gabriel A. and Brian J. Soden. 2007. Effect of remote sea surface temperature change on tropical cyclone potential intensity. Nature. Vol. 450: 1066-1070.

Last updated: November 2, 2011

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