Climate and Water Resource Case Study

Overview of Climate Change
Greenhouse Effect and Climate Change
What is the world doing about climate change?
Investigating Regional and Local Projected Climate Change
Consequences of Predicted Climate Change: Focus on Oahu, Hawaii
Chapter 7 title
Chapter 8 title

Chapter 5 - B. Oahu Overview


There are too many islands in the Pacific to investigate future climate impacts on all of them in this case study. We will instead spend the remainder of the case study focusing on future climate impacts on the island of Oahu, which is part of the state of Hawaii. Oahu is not necessarily representative of small, low-lying Pacific Islands such as atolls. It is a relatively large island compared to most Pacific Islands, has a large population near 1 million, and a bustling economy. However, it is useful to examine closely because much is known about its geology, geography, weather, and economy. All this aids in projecting how future climate change with impact Oahu and thus can be useful in determining what impacts might occur to other islands.

Oahu Characteristics

           The nearest continental land mass is over 3,864 kilometers (2,400 miles) away making Hawaii one of the world’s most remote group of islands (Figure 16). Hawaii’s climate is also one of the most diverse on the planet. Of all the major 11 different biomes on Earth, only tundra is not found in Hawaii. The surrounding tropical ocean supplies moisture to the air year round. This supply of moisture acts likes a thermostat and keeps seasonal temperature variations to a minimum. The warmest months are August thru September and the coolest months are January thru February. The islands are usually bathed in northeasterly trade winds due to a semi-permanent atmospheric high pressure cell that is situated northeast of the islands.

Figure 16. Pacific Island Map.

            The elevation of Hawaii’s mountains and ridges significantly influences the local weather and climate. In Hawaii, rainfall amount and distribution closely follow the topographic contours of the islands. Rainfall is greatest at ridges and windward areas (northeast slope of ridges and mountains) and is least in leeward lowlands (see below orographic rainfall description). Mt. Waialeale on the island of Kauai is one of the wettest places on Earth receiving 1016 centimeters (400 inches) of rain per year. Elevated windward sides of the islands can receive more than 508 centimeters (200 inches) per year, and leeward areas can receive as little as 38 centimeters (15 inches) per year. The leeward areas have mostly dry warm months and receive most of their rainfall accumulation during the winter storms. The windward regions tend to show smaller seasonal variations because persistent trade wind generated showers govern their rainfall accumulation. El Niño conditions usually disrupt these patterns resulting in drought conditions for the entire state and more frequent hurricanes and tropical storms.

            Described by Mark Twain as “the loveliest fleet of islands that lies anchored in any ocean”, Hawaii is comprised of 221 kilometers (137 miles) of islands encompassing a land area of 16,686 square kilometers (6,442.6 square miles). There are 8 major Hawaiian Islands: Kauai, Oahu, Lanai, Molokai, Maui, Niihau, Kahoolawe, and Hawaii (sometimes referred to as the “Big Island of Hawaii”). The islands were discovered by Polynesian explorers between the 3rd and 7th century AD and later by the British captain James Cook in 1778. Hawaii became the 50th state in the U.S. union in 1959. Honolulu, the capital city, is located on the island of Oahu. The state resident population in 2000 was a little over 1.2 million with 876,156 residing on the island of Oahu and a yearly population growth at 0.9%. The gross state product in 2000 was 39.1 billion U.S. dollars and the annual per capita income (in 1999) was $27,533. Age breakdown for Hawaii in 2000: Under 5 years old (6.5%); 5-19 years old (20.6%); 20-44 years old (36.8%); 45-64 years old (22.9%); 65+ years old (13.3%). The median age is 36.2 years old.

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