Climates of the Pacific Islands

Climates of the Pacific Islands

Main Contents

  • Definition of Climate and Weather

    • Associated factors.

  • Climate Change

    • The main components and issues of Pacific Islands Climate.

Climate of the Pacific Islands

  • The ITCZ (Intertropical Convergence Zone)

  • El Nino & La Nina (ENSO - El Niño-Southern Oscillation)

  • Tropical Cyclones

  • Climate Change

  • Greenhouse Effect

  • Sea Level Rise

  • Ozone Layer

  • Solutions to Global Warming

  • Governments’ roles in combating the impacts of climate change.

Overall Recap

  • Water's Role in Climate

    • Water plays several roles in global climate.

    • Water as a Greenhouse Gas: Water is a greenhouse gas, meaning it absorbs and emits longwave radiation, enhancing atmospheric warming.

    • Precipitation: Precipitation is another significant form of water in the global climate. More water vapor and clouds in the air lead to more precipitation.

    • Temperature Reduction: Water reduces global temperature in arctic and subarctic zones.

Weather Systems & Climate

  • Interdependence: Weather and climate are not independent; changes in climate lead to changes in weather patterns.

  • Climate Definition: Climate is what you expect (e.g., a hot summer), while weather is what you get (e.g., a cool day in August).

  • Weather Definition: Weather is the behavior of the atmosphere at any given moment.

    • It is observed daily or weekly and includes sunshine, rain, cloud cover, wind, etc.

    • It can change from minute to minute, hour to hour, day to day, season to season.

What Causes Weather?

  • Energy Transfer: Weather is caused by the transfer of energy between the Sun, Earth's surface, and the Atmosphere.

    • The sun warms the earth's surface, increasing its temperature.

    • The sun's energy evaporates water, adding moisture to the air.

    • Hot air rises and cools.

    • Water vapor condenses to form clouds and precipitation.

    • Unequal heating and differences in air pressure cause wind.

Climate

  • Definition: Climate is the long-term aggregation of weather in an area and the extent to which those conditions vary over long time intervals.

    • It considers patterns of precipitation, temperature, humidity, sunshine, fog, frost, soil, and moisture temperature over long periods in a particular place.

  • Determining Factors of a Region's Climate:

    • Location (latitude & longitude)

    • Altitude (height above sea level)

    • Air Pressure

    • Wind patterns

    • Rainfall

Determining Factors of Climate

  • Latitude

  • Altitude

  • Air Masses

  • High & Low Pressure Zones

  • Heat Exchange from Ocean currents

  • Distribution of mountain barriers

  • Patterns of prevailing winds

  • Distribution of land masses and the seas

Wind Systems in Climate

  • Role of Winds: Winds carry our weather around the world.

  • Influences on Wind: Winds are influenced by incoming solar energy, Earth’s rotation, and the distribution of land and sea.

  • Wind Creation: Warm, lighter air rises, while cool, denser air flows beneath it, creating a low-pressure zone. This creates wind.

  • Seasonal Wind Direction Changes: Winds blow in different directions in different seasons due to three factors:

    1. Incoming solar energy at any latitude.

    2. The Earth’s rotation.

    3. Distribution of land and sea.

Prevailing Winds

  • Seasonal Patterns: Prevailing winds create patterns which are very different in January and July.

    • Westerlies: Blow more strongly in January in the Northern Hemisphere and constantly in the Southern Hemisphere.

    • Monsoon Winds: Blow from Asia in January and North from Australia in July.

    • Doldrums: Windless regions near the Equator.

Latitudes & Climate

  • Earth’s Rotation and Climate

    • Includes a diagram showing the distribution of cold deserts, forests, and hot deserts at different latitudes (60ºN, 30ºN, 0º, 30ºs, 60ºS) with prevailing winds (Westerlies, Northeast trades, Southeast trades).

Incoming Solar & Climate

  • Diagram showing:

    • Arctic Circle at 66.5° N

    • Tropic of Cancer at 23.5° N

    • Equator

    • Tropic of Capricorn at 23.5° S

  • Summer Solstice (June 21-22): Incoming solar energy greatest in the Northern Hemisphere

  • Vernal Equinox (March 21-22): Incoming solar energy equal in both hemispheres

  • Autumnal Equinox (September 22-23)

  • Winter Solstice (December 21-22): Incoming solar energy greatest in the Southern Hemisphere

Air Pressure Relations to Weather and Climate

  • Variability: Air pressure varies from place to place and time to time.

  • Influences: Influenced by altitude, temperature, earth’s rotation, distribution on land/ocean.

    • Low Pressure: Occurs when air is heated, rises, expands, and cools. The weight of the air is low (light), resulting in bad weather.

    • High Pressure: Occurs when air descends. The weight of cool air is high (heavy), meaning fine weather.

    • Wind Direction: Winds always blow from High-Pressure areas to Low-Pressure Areas.

Air Pressure over Land and Water

  • Land vs. Water: Air over land heats up and rises, creating an area of low pressure. Air over water remains cooler due to the ocean's heat capacity.

  • Wind Creation: Air moves from high pressure to low pressure, creating wind.

Cyclones and Anti-cyclones

  • Cyclones: Low-pressure systems which bring bad weather (also called depressions).

    • Air moves towards the center.

    • Moves in a clockwise direction in the Southern Hemisphere and anti-clockwise direction in the Northern Hemisphere.

    • Referred to as hurricanes in the USA and typhoons in China.

  • Anti-cyclones: High-pressure system which brings fine weather.

    • Air moves outwards from the center.

    • Moves anticlockwise in the Southern Hemisphere and clockwise in the Northern hemisphere.

Measuring Weather

  • Meteorologists: Scientists who study the weather/climate of an area and measure various factors:

    • Temperature: Measured in degrees Celsius using a thermometer.

    • Sunshine: Measured in hours using a sunshine recorder.

    • Wind: Measured by speed using an anemometer and direction using a wind vane.

    • Rainfall: Measured in millimeters using a rain gauge.

Inter-Tropical Convergence Zone (ITCZ)

  • Definition: The ITCZ is a zone where the Northeast and Southeast Trade winds converge and form an area of Low Pressure.

  • Movement: The ITCZ moves north or south of the Equator as the earth moves around the sun during the year.

    • Example: In January, it is winter in the North Pacific and summer in the South Pacific; in July, it is summer in the North Pacific and winter in the South Pacific.

  • Island Climate Dependency: The climate of each Island Group depends on its location in relation to the ITCZ.

    • Islands under the ITCZ (like Samoa, Cook Islands, Tonga, and Fiji) have cloudy, high rainfall climates.

    • Islands near the High-Pressure zones (like New Caledonia) have sunnier, drier climates.

ITCZ Diagram

  • Diagram showing the position of the ITCZ in January and July, with its maximum north and south extent.

    • Maximum North = 25°

    • Maximum South = 20°

    • Tropic of Cancer = 23.5°

    • Tropic of Capricorn = 23.5°

Lecture Overview

  • Difference between Climate and Weather

  • Types of winds, Air Pressure

  • What determines climate

  • EL Nino & La Nina

  • Consequences of Climate Change

  • Greenhouse effect, Global warming

  • Solutions to Global Warming

El Nino Southern Oscillation (ENSO)

  • Importance: An important feature which also determines the differences in climates in PICs is the effect of relief on winds and rainfall, sea-surface temperatures, and the El Nino phenomenon.

  • ENSO Definition: The ENSO is the term scientists use to describe the entire warm (El Nino) and cold (La Nina) oscillation phases of sea-surface temperatures of the Pacific Ocean and atmosphere temperatures.

  • Southern Oscillation Index (SOI): The measure of the strength of the trade winds.

Normal Year (La Nina) vs El Nino Diagrams

  • Normal Year (La Nina)

    • Walker circulation

    • Trade winds blowing westwards

    • Warm surface water piling up

    • Australia

    • Indonesia

    • Cold water pressing upwards replacing the warm surface water

    • Increased convection

  • El Niño Year

    • When trade winds drop

    • Warm surface water may flow eastwards

    • Australia

    • Indonesia

    • Warm sea currents replace the cold water and establishes a deep layer of warm water along the coast

El Nino

  • Pressure Flip-Flop: When the Southern Oscillation occurs, the pressure over the eastern and western Pacific flip-flops. This causes the trade winds to diminish, leading to an eastward movement of warm water along the equator.

  • Warming Waters: As a result, the surface waters of the central and eastern Pacific warm, with far-reaching consequences to weather patterns.

  • Temperature Increase: Ocean temperatures of 4-6 °F above average are commonly observed between the International Dateline and the west coast of South America.

  • Rain and Thunderstorms: Warm ocean waters cause increases in tropical rain and thunderstorms.

  • Atmospheric Pressure: Atmospheric pressure increases near Indonesia and in the western Pacific and decreases in the eastern Pacific.

  • Jet Stream: Pressure changes lead to the subtropical jet stream moving into Florida, southern Georgia, and Alabama, steering cloudy, rain-bearing systems into the region in winter.

  • Hurricanes: Because of changes in jet stream strength, hurricanes are less likely.

  • Duration: El Niño lasts for no more than one year.

  • Tornadoes: The likelihood of tornadoes and severe weather increases in the Florida peninsula.

La Niña

  • Temperature Decrease: Ocean temperatures of 4-6 °F below average are observed in the eastern Pacific Ocean.

  • Thunderstorm Location: Cold water in the eastern Pacific shifts the location of thunderstorms, rising air, and lower pressure to the western Pacific.

  • Nutrients: Cold water from the deep ocean provides increased nutrients for fish and plankton, leading to improved fishing and sustenance for birds and other predators in the eastern Pacific Ocean.

  • Jet Stream Shift: Pressure shifts cause the subtropical jet stream in the U.S. to shift north, moving the storm track to northern Georgia and Alabama and leaving Florida sunnier and drier than usual.

  • Duration: La Niña can last for one to three years.

  • Tornadoes: The likelihood of tornadoes and severe weather increases in Alabama and Georgia.

Ocean Currents

  • Diagram showing various ocean currents including:

    • N. Pacific, Alaska, Labrador, Irminger, N.Atlantic Drift, Greenland, Canary, California, Gulf Stream, Oyashio, Kuroshio, N. Equatorial, Equatorial Counter, S. Equatorial, Peru, Benguela, W. Australia, Brazil, E. Australia, Agulhas, S. Pacific, Antarctic Circumpolar, S. Atlantic, S. Indian, Antarctic Subpolar

Cyclone Winds

  • Wind Structure: Diagram showing wind structure within a cyclone with indications for moderately strong winds (red), very strong winds (purple), and the calm eye of the cyclone.

Important Concepts

  • CLIMATE CHANGE: Long-term change in temperature and weather patterns.

  • GLOBAL WARMING: Increase in the surface temperature due to human activities.

  • CARBON EMISSION: Carbon dioxide as the highest release gas into the air.

  • GREEN HOUSE GASES AND EFFECTS: Gases emitted in the atmosphere.

  • SEA LEVEL RISE: Impacts of climate change.

  • MITIGATION STRATEGIES: How governments are responding.

Obvious Signs of Climate Change

  • Less Snowpack

  • Shrinking Sea Ice

  • Melting Glaciers

  • Thawing Permafrost

  • Higher Temperatures

  • Warmer Oceans

  • Increased Ocean Acidity

  • Wilder Weather

  • Changing Snow Patterns

  • More Rain and Droughts

  • Rising Sea Level

Hottest Year on Record

  • 2024 was the hottest year on record.

  • Global average temperature by year, compared with the pre-industrial average, 1850-1900.

  • Includes a graph showing temperature increase above the pre-industrial average.

    • +1.5C

    • +1.0C

    • +0.5C

Climate Change & The Pacific Isles

  • Climate Instability: The earth’s climate is unstable and constantly changing between cold and warm phases. People continue to evolve and adapt to these changes.

  • Continuous Change: The earth’s climate is continually changing from day to day and season to season.

  • Example: The Ice Age 18,000 years ago, temperature was cooler in the Pacific, and mountain peaks in PNG and NZ were permanently covered with ice drawn from the ocean, hence a lower sea level.

  • Post-Ice Age: This was followed by a rise in temperature, melting of ice, rising of sea level, and people were more mobile.

  • Sea Level Stabilization: 5000 years ago: sea level stabilised, followed by a cooler temperature and a fall in sea level.

  • Human Impact: These changes in the climate have been greatly intensified by human activities: global warming and its consequences.

  • Environmental Consequences: The Pacific has been and is experiencing the environmental consequences of climate change.

  • Increasing Emissions: Increasing emission of CFC gases into the atmosphere – global warming.

  • Criticism of Developed Nations: Developing countries, the Pacific included, have vigorously criticized the developed nations for their carbon emission.

  • Passive Victims: The Pacific small island nations are the passive victims of this emission.

Global Warming Definition

*Global Warming is the increase of Earth and Ocean's average surface temperature due to effect of greenhouse gases, such as carbon dioxide emissions from burning fossil fuels or from deforestation.

Green House Effect

  • Temperature Regulation: The Earth supports the life of humans, animals, and plants by ensuring a constant temperature.

  • Green House Effect: The sun’s heat is absorbed by the earth’s surface and changed to long wave radiation (infra –red rays) which is absorbed by water vapor and carbon dioxide.

    • Without this effect, the heat would be lost, and the earth would be very cold.

Global Greenhouse Gas Emissions by Gas

  • Carbon Dioxide (fossil fuel and industrial processes): 65%

  • Carbon Dioxide (forestry and other land use): 11%

  • Methane: 16%

  • Nitrous Oxide: 6%

  • F-gases: 2%

Greenhouse Effect Diagram

  • Diagram illustrating the greenhouse effect:

    • Rays of sunlight penetrate the lower atmosphere and warm the earth's surface.

    • The earth's surface absorbs much of the incoming solar radiation and degrades it to longer-wavelength infrared (IR) radiation, which rises into the lower atmosphere. Some of this IR radiation escapes into space as heat, and some is absorbed by molecules of greenhouse gases and emitted as even longer wavelength IR radiation, which warms the lower atmosphere.

    • As concentrations of greenhouse gases rise, their molecules absorb and emit more infrared radiation, which adds more heat to the lower atmosphere.

  • Green House Gases:

    • Carbon dioxide, water vapor, ozone, methane, nitrous oxide, and chlorofluorocarbons.

  • Human Impact:

    • Human activities (burning fossil fuels and industrialization) have released too much greenhouse gases back into the atmosphere and caused global temperatures to rise and the climate to change.

Carbon Dioxide Increase

  • Graph of Increases in Average Atmospheric Carbon Dioxide Since 1860

    • Parts per million:

      • 1800: 260

      • 1900: 310

      • 2000: 360

      • 2100: 410

Shrinking Arctic Sea Ice

  • Diagrams showing the extent of Arctic Sea Ice in 1979 and 2003, illustrating the shrinking ice cover.

Rising Sea Levels Threaten Islands

  • Image depicting the threat of rising sea levels to islands.

Sea Level Rise in Tuvalu

  • Image illustrating the impact of sea-level rise in Tuvalu.

Impacts of Sea Level Rise

  • Coastal erosion

  • Flooding of coastal towns, cities, villages, farms, infrastructure, and amenities.

  • Socio-economic losses in tourism and agriculture.

  • Cultural and political implications on island nations of the Pacific and their people.

  • Displacement of peoples – Tuvalu, Kiribati etc.

Ozone Layer

  • Ozone Layer Definition: Stratospheric layer of gaseous ozone that protects life on earth by filtering out most harmful ultraviolet radiation from the sun.

  • Ozone Depletion: Decrease of ozone concentration in the stratosphere. This will have serious effects on human health, animal life, and plants (producers) that support earth’s food chains and food webs.

Consequences of Ozone Loss

  • Natural Capital Degradation

  • Human Health

    • Worse sunburn

    • More eye cataracts

    • More skin cancers

    • Immune system suppression

  • Food and Forests

    • Reduced yields for some crops

    • Reduced seafood supplies from reduced phytoplankton

    • Decreased forest productivity for UV-sensitive tree species

  • Wildlife

    • Increased eye cataracts in some species

    • Decreased population of aquatic species sensitive to UV radiation

    • Reduced population of surface phytoplankton

    • Disrupted aquatic food webs from reduced phytoplankton

  • Air Pollution and Materials

    • Increased acid deposition

    • Increased photochemical smog

    • Degradation of outdoor paints and plastics

  • Global Warming

    • Accelerated warming because of decreased ocean uptake of CO_2 from atmosphere by phytoplankton and CFCs acting as greenhouse gases

Solutions to Global Warming

  • Prevention

    • Cut fossil fuel use (especially coal)

    • Shift from coal to natural gas

    • Improve energy efficiency

    • Shift to renewable energy resources

    • Reduce deforestation

    • Use more sustainable agriculture

    • Limit urban sprawl

    • Reduce poverty

    • Slow population growth

  • Cleanup

    • Remove CO_2 from smokestack and vehicle emissions

    • Store CO_2 by planting trees

    • Store CO_2 deep underground

    • Store CO_2 in soil by using no-till cultivation and taking crop land out of production

    • Store CO_2 in the deep ocean

    • Repair leaky natural gas pipelines and facilities

Government Roles in Reducing the Threat of Climate Change

  • Funding for carbon dioxide removal technologies.

  • Carbon taxes.

  • Energy taxes.

  • Technology transfer.

Additional Reading – The Case of Samoa

  • Reference to a Singapore Journal of Tropical Geography article on climate change and community resilience in Samoa.