Introduction

In this section... Historical Climate Trends Possible Future Climates

Copyright © 2002 Photodisc Inc

This paper focuses on the US and US-affiliated islands of the Caribbean and Pacific.  This includes Puerto Rico, and the US Virgin Islands in the Caribbean and the Hawaiian Islands, American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, the Federated States of Micronesia, the Republic of the Marshall Islands, and the Republic of Palau in the Pacific.  The last three are independent states in free association with the United States.  Hawaii became the 50^th state of the US in 1959.  The Virgin Islands, Guam, and American Samoa are US territories.  The Northern Mariana Islands and Puerto Rico are commonwealths.  Much of this information also would apply to the Florida Keys.  Stretching southwest for about 150 miles into the Gulf of Mexico from Biscayne Bay at Miami, Florida, are the Florida Keys, a small group of islands and reefs. 

Islands contain diverse and productive ecosystems, and include many specialized and unique species.  Many islands are facing the stresses of rapid human population growth, increasing vulnerability to natural disasters, and deteriorating natural resources.  Droughts and floods are among the climate extremes of most concern as they affect the quality of water supplies in island communities, and thus can have significant health consequences.  Due to their small size and isolation, many islands face chronic water shortages and problems with waste disposal.  Some are facing a species extinction crisis. For example, the Hawaiian Islands have the highest extinction rate of any state in the nation.  Biological invasion (invasive, non-native species of plants and animals that out-compete the native flora and fauna) and habitat destruction seem to be the primary causes of the extinction crisis.  Over harvesting of reef organisms is also a problem in some Pacific regions.

For most island communities, transportation and other social infrastructure (e.g., communities) and economic activities are located near the coast making them highly vulnerable to storms, cyclones, and sea-level fluctuations.  This vulnerability is especially related to storm waves that can be higher because of a combination of sea-level rise and beach erosion.  Changes in storm frequency, direction, and behavior (e.g., duration) can also influence the size and strength of waves.  Tropical cyclones with more precipitation resulting from global warming (because there is more moisture in the atmosphere) could cause tremendous damage on island communities from the amount of rain they could bring.  Combining that increased amount of rain with island topography could lead to landslides and flash flooding even if storm intensity doesn't increase. 

Historical Climate Trends

Over the 20^th  century, average annual air temperatures in the Caribbean Islands have increased by more than 1°F (0.6°C).  Average annual air temperatures in the Pacific Islands have increased by about 0.4°F (0.2°C).  Globally, sea level has risen by 4 to 8 inches in the past 100 years, with important local differences.  The current rate of sea-level increase in the Caribbean and Gulf of Mexico is about 3.9 inches per 100 years.  In the Pacific region, as around the globe, absolute sea level is also rising.  However, because the land of some islands are naturally rising it is difficult to see sea-level rise compared to land levels, so a regional long-term average trend in relative sea level in the Pacific is difficult to determine.  Making the sea level issue in the Pacific even more complicated is the fact that there are extreme tides and changes in sea levels associated with storms, lunar tides, and the El Niño-Southern Oscillation phenomenon (ENSO).

Possible Future Climates

For the Caribbean and the Pacific, both of the key models used here project increasing air and water temperatures.  For the Caribbean, both models project slightly wetter conditions in winter with the models disagreeing on changes in precipitation for summer -- from slightly drier conditions everywhere to some parts being wetter and some parts drier.  For the Pacific near the equator, both models show greater warming in the central and eastern parts and a shift toward the east for precipitation (means less precipitation for the western Pacific Islands).  It is also possible that El Niño patterns (strength, frequency, and duration) and hurricane and typhoon patterns will change.  Some models project that extreme El Niño/La Niña events are likely to increase with increasing greenhouse gas concentrations.  While we are not yet sure how the frequency and storm track patterns will change, some studies suggest that wind speeds for storms, hurricanes, and typhoons could increase.  There could be changes to other naturally occurring variations in weather, ocean temperature, and currents as well that could have impacts for the islands regions.