Chapter 21Chapter 21Global Climate ChangeGlobal Climate Change

Overview of Chapter 21Overview of Chapter 21

Introduction to Climate ChangeIntroduction to Climate Change Causes of Global Climate ChangeCauses of Global Climate Change

Effects of Climate ChangeEffects of Climate Change Melting Ice and Rising Sea LevelMelting Ice and Rising Sea Level Changes in Precipitation PatternsChanges in Precipitation Patterns Effects on OrganismsEffects on Organisms Effects on Human HealthEffects on Human Health Effects on AgricultureEffects on Agriculture

Dealing with Global Climate ChangeDealing with Global Climate Change

Climate Change Climate Change TerminologyTerminology Greenhouse GasGreenhouse Gas

Gas that absorbs infrared radiationGas that absorbs infrared radiation Positive FeedbackPositive Feedback

Change in some condition triggers a response Change in some condition triggers a response that intensifies the changed condition that intensifies the changed condition

Infrared RadiationInfrared Radiation Radiation that has a wavelength that is longer Radiation that has a wavelength that is longer

than that of visible light, but shorter than that of than that of visible light, but shorter than that of radio waves radio waves

Greenhouse EffectGreenhouse Effect Increase of heat in a system where energy enters Increase of heat in a system where energy enters

(often as light), is absorbed as heat, and released (often as light), is absorbed as heat, and released sometime later sometime later

Natural Physical Factors Affecting Natural Physical Factors Affecting Climate:Climate: 1.1. Latitude: Latitude:

• near equator is warm, near poles is cold, because near equator is warm, near poles is cold, because at equator the Sun strikes Earth at a at equator the Sun strikes Earth at a higher angle higher angle of insolationof insolation, at poles Sun strikes Earth at a , at poles Sun strikes Earth at a lower angle of insolationlower angle of insolation

Natural Physical Factors Affecting Natural Physical Factors Affecting Climate:Climate:

1.1. Latitude…continued: Latitude…continued: • Seasons on Earth are determined by Seasons on Earth are determined by

latitude and angle of insolation at various latitude and angle of insolation at various times throughout the year, and are caused times throughout the year, and are caused by:by:• Tilt of Earth’s axisTilt of Earth’s axis

• Earth’s revolution around the SunEarth’s revolution around the Sun

• Parallelism of Earth’s axisParallelism of Earth’s axis

Seasons on Earth…Seasons on Earth…

Natural Physical Factors Affecting Natural Physical Factors Affecting Climate:Climate:

2.2. Proximity to a large body of water Proximity to a large body of water (ocean or large lake):(ocean or large lake):

• Water has a high specific heat, so Water has a high specific heat, so the ocean does NOT heat up or cool the ocean does NOT heat up or cool down easily, and therefore helps to down easily, and therefore helps to regulate temperatures of nearby regulate temperatures of nearby coastal areascoastal areas

Natural Physical Factors Affecting Natural Physical Factors Affecting Climate:Climate:3.3. Nearness to mountains:Nearness to mountains:

• Higher elevations have colder avg. Higher elevations have colder avg. temperatures, longer snowpack, etc.temperatures, longer snowpack, etc.

• Orographic effect: (rainshadow)Orographic effect: (rainshadow)– Windward side of mountains force air to rise, Windward side of mountains force air to rise,

expand, cool, and cause water vapor to expand, cool, and cause water vapor to condense, forming clouds and abundant condense, forming clouds and abundant rainfallrainfall

– Leeward side of mountains experience dry Leeward side of mountains experience dry conditions as air sinks…called the conditions as air sinks…called the “rainshadow” side.“rainshadow” side.

Orographic (Mountain) Effect:Orographic (Mountain) Effect:

Natural Physical Factors Affecting Natural Physical Factors Affecting Climate:Climate:

4.4. Wind Circulation Wind Circulation Patterns – caused by Patterns – caused by unequal heating of the unequal heating of the Earth, which creates Earth, which creates different temperature different temperature zones, which creates zones, which creates different pressure belts, different pressure belts, which forces the major which forces the major wind belts to occur, wind belts to occur, which determines major which determines major weather and climate weather and climate patternspatterns

Natural Physical Factors Affecting Natural Physical Factors Affecting Climate:Climate:

5.5. Ocean Circulation Patterns:Ocean Circulation Patterns:• Prevailing wind belts create mass Prevailing wind belts create mass

movements of ocean water (currents)movements of ocean water (currents)• Circular ocean currents are called “gyres”Circular ocean currents are called “gyres”• Ocean currents are also influenced by the Ocean currents are also influenced by the

Coriolis effect, and tend to circulate Coriolis effect, and tend to circulate clockwise in the N. hemisphere, and clockwise in the N. hemisphere, and counterclockwise in the S. hemispherecounterclockwise in the S. hemisphere

• Ocean currents are forced to move around Ocean currents are forced to move around major landmasses (continents and islands)major landmasses (continents and islands)

Earth’s Major Ocean CurrentsEarth’s Major Ocean Currents

Natural Physical Factors Affecting Natural Physical Factors Affecting Climate:Climate:

6.6. Ocean-Atmosphere InteractionsOcean-Atmosphere Interactions• Ocean interacts with the atmosphere to Ocean interacts with the atmosphere to

dramatically influence climate patterns dramatically influence climate patterns worldwideworldwide

• El Nino & La Nina can impact global climate El Nino & La Nina can impact global climate in any given yearin any given year

Long-Term Natural Factors Long-Term Natural Factors Affecting ClimateAffecting Climate• Paleoclimatology – the study of climate changes Paleoclimatology – the study of climate changes

over the history of the Earthover the history of the Earth• A variety of techniques and inferences are used A variety of techniques and inferences are used

to measure or infer atmospheric gas content, to measure or infer atmospheric gas content, temperatures, dust particles, life forms, etc.temperatures, dust particles, life forms, etc.

• Methods Used to Determine Past Climate:Methods Used to Determine Past Climate:1.1. Recorded Human Observations (only reliable for past Recorded Human Observations (only reliable for past

200 yrs.)200 yrs.)2.2. Ice Core DataIce Core Data3.3. Tree RingsTree Rings4.4. Soil SedimentsSoil Sediments5.5. Biological FossilsBiological Fossils

– Shells of aquatic organismsShells of aquatic organisms– CoralsCorals

Ice Core Data:Ice Core Data:

• Drilled from deep within the ground, ice cores Drilled from deep within the ground, ice cores can be used to measure increases and/or can be used to measure increases and/or decreases in snowfall over time as well as decreases in snowfall over time as well as changes in atmospheric gases as seen in changes in atmospheric gases as seen in trapped air bubbles, dust, and oxygen isotopes. trapped air bubbles, dust, and oxygen isotopes.

• Scientists drilling in the Greenland ice sheet Scientists drilling in the Greenland ice sheet have been able to piece together a climate have been able to piece together a climate record dating back approximately 110,000 yearsrecord dating back approximately 110,000 years

• Antarctic ice samples have yielded information Antarctic ice samples have yielded information as far back as 750,000 years. as far back as 750,000 years.

• Ice cores can provide vast amounts of Ice cores can provide vast amounts of information, including an annual record of information, including an annual record of temperature, precipitation, atmospheric temperature, precipitation, atmospheric composition, volcanic activity, and even wind composition, volcanic activity, and even wind patterns.patterns.

Ice Core Data:Ice Core Data:

• Specifically, COSpecifically, CO22 and CH and CH44 concentrations concentrations can be analyzed and used to infer past can be analyzed and used to infer past temperatures.temperatures.

• Thickness of ice layers also reflects Thickness of ice layers also reflects temperature and precipitation in the past.temperature and precipitation in the past.

• Atmospheric dust particles can also be Atmospheric dust particles can also be analyzed from ice cores.analyzed from ice cores.

Vostok Vostok Ice Ice

Core Core Data:Data:

Long-term natural influences on Long-term natural influences on climate…global changesclimate…global changes• There are several LONG-TERM changes that There are several LONG-TERM changes that

have influenced climate in a cyclic manner.have influenced climate in a cyclic manner.

• Milankovitch Cycles are the collective Milankovitch Cycles are the collective effect of changes in the Earth's movements effect of changes in the Earth's movements upon its climate, named after Serbian civil upon its climate, named after Serbian civil engineer and mathematician Milutin engineer and mathematician Milutin Milanković Milanković

• Variations in the Earth's eccentricity, axial Variations in the Earth's eccentricity, axial tilt, and precession comprise the three tilt, and precession comprise the three dominant cycles dominant cycles

Milankovitch Cycles: EccentricityMilankovitch Cycles: Eccentricity

• Eccentricity is, simply, the Eccentricity is, simply, the shape of the Earth's orbit shape of the Earth's orbit around the Sun. around the Sun.

• This constantly fluctuating, This constantly fluctuating, orbital shape ranges between orbital shape ranges between more and less elliptical (0 to 5% more and less elliptical (0 to 5% ellipticity) on a cycle of about ellipticity) on a cycle of about 100,000100,000 years. years.

• These oscillations, from more These oscillations, from more elliptic to less elliptic, are of elliptic to less elliptic, are of prime importance to glaciation prime importance to glaciation in that it alters the distance in that it alters the distance from the Earth to the Sun, thus from the Earth to the Sun, thus changing the distance the Sun's changing the distance the Sun's short wave radiation must short wave radiation must travel to reach Earth, travel to reach Earth, subsequently reducing or subsequently reducing or increasing the amount of increasing the amount of radiation received at the radiation received at the Earth's surface in different Earth's surface in different seasons. seasons.

Animated sequence

Milankovitch Cycles: Axial TiltMilankovitch Cycles: Axial Tilt

• Axial tilt is the inclination of the Earth's axis in relation Axial tilt is the inclination of the Earth's axis in relation to its plane of orbit around the Sun. to its plane of orbit around the Sun.

• Oscillations in the degree of Earth's axial tilt occur on a Oscillations in the degree of Earth's axial tilt occur on a periodicity of periodicity of 41,000 41,000 years from 21.5 to 24.5 degrees.years from 21.5 to 24.5 degrees.

• A larger tilt will result in warmer summers and colder A larger tilt will result in warmer summers and colder winters!winters!

Milankovitch Cycles: Precession Milankovitch Cycles: Precession (wobble)(wobble)• Precession is the Earth's slow wobble as it Precession is the Earth's slow wobble as it

spins on axis. This wobbling of the Earth on its spins on axis. This wobbling of the Earth on its axis can be likened to a top running down, and axis can be likened to a top running down, and beginning to wobble back and forth on its axis. beginning to wobble back and forth on its axis.

• The precession of Earth wobbles from pointing The precession of Earth wobbles from pointing at Polaris (North Star) to pointing at the star at Polaris (North Star) to pointing at the star Vega. Vega.

• When this shift to the axis pointing at Vega When this shift to the axis pointing at Vega occurs, Vega would then be considered the occurs, Vega would then be considered the North Star. This top-like wobble, or precession, North Star. This top-like wobble, or precession, has a periodicity of about has a periodicity of about 23,00023,000 years. years.

Milankovitch Cycles: Precession Milankovitch Cycles: Precession (wobble)(wobble)

Animated sequence

Milankovitch Cycles…overall Milankovitch Cycles…overall effect:effect:

Current Observations of Current Observations of ClimateClimate• Today, a wide variety of instruments has Today, a wide variety of instruments has

been deployed to continuously measure a been deployed to continuously measure a large number of climate factors including:large number of climate factors including:– Air temperatureAir temperature– Sea surface temperatureSea surface temperature

– Greenhouse Trace Gas concentrations (COGreenhouse Trace Gas concentrations (CO22, , CHCH44, O, O33, NO, NO, NO, NO22, etc., etc.

– Response of plants (budding times, size, etc.)Response of plants (budding times, size, etc.)– Response of animals (changes in range, Response of animals (changes in range,

timing of reproduction, etc.)timing of reproduction, etc.)

Introduction to Climate Introduction to Climate ChangeChange Evidence for Climate ChangeEvidence for Climate Change

14 warmest years since mid-1800s have 14 warmest years since mid-1800s have occurred since 1990occurred since 1990

Phenological spring in N. hemisphere Phenological spring in N. hemisphere now begins 6 days earliernow begins 6 days earlier

Warming is not due to natural causesWarming is not due to natural causes Human produced greenhouse gases are Human produced greenhouse gases are

most plausible explanationmost plausible explanation

Introduction to Climate Introduction to Climate Change: Mean Annual Change: Mean Annual Global Temperature 1960–Global Temperature 1960–20072007

Causes of Climate ChangeCauses of Climate Change

Greenhouse gas concentrations Greenhouse gas concentrations increasingincreasing

Causes of Climate ChangeCauses of Climate Change

Increased Increased concentration of concentration of COCO22 (right) (right) Burning fossil fuels Burning fossil fuels

in cars, industry in cars, industry and homesand homes

DeforestationDeforestation Burning of forestsBurning of forests

Greenhouse EffectGreenhouse Effect

Pollutants That Cool the Pollutants That Cool the AtmosphereAtmosphere

Atmospheric Aerosols Atmospheric Aerosols Both human and natural sourcesBoth human and natural sources Tiny particles that remain in troposphere Tiny particles that remain in troposphere

for weeks or monthsfor weeks or months Often contain sulfurOften contain sulfur

Complicates models of climate Complicates models of climate changechange

Climate ModelsClimate Models

Climate affected by:Climate affected by: winds, clouds, ocean currents, and albedo winds, clouds, ocean currents, and albedo

Used to explore past climate eventsUsed to explore past climate events Advanced models can project future Advanced models can project future

warming eventswarming events Models are only as good as the data Models are only as good as the data

and law used to program themand law used to program them They have limitationsThey have limitations

Climate ModelsClimate Models

Effects of Global Climate Effects of Global Climate ChangeChange Wildfire in CaliforniaWildfire in California

Effects of Global Climate Effects of Global Climate Change: Melting Ice and Change: Melting Ice and Rising Sea LevelsRising Sea Levels Sea level rise caused in 2 waysSea level rise caused in 2 ways

Thermal ExpansionThermal Expansion Melting of land iceMelting of land ice

Melting has positive feedbackMelting has positive feedback Increased melting decreases ice, which Increased melting decreases ice, which

decreases albedo leading to further decreases albedo leading to further warmingwarming

19519577

19919988

Glacier National ParkGlacier National Park

Melting Ice and Rising Sea Melting Ice and Rising Sea LevelsLevels

Case-In-Point Impacts in Case-In-Point Impacts in Fragile AreasFragile Areas

Eskimo Inuit liveEskimo Inuit livetraditional lifetraditional lifedictated by freezingdictated by freezingclimateclimate

Climate change isClimate change isaltering their existencealtering their existence Wildlife displacedWildlife displaced Reduced snow cover and shorter river ice Reduced snow cover and shorter river ice

seasonsseasons Thawing of permafrost (right)Thawing of permafrost (right)

Effects of Global Climate Effects of Global Climate Change: Changing Change: Changing Precipitation PatternsPrecipitation Patterns Some areas will get more water, Some areas will get more water,

some areas will have greater some areas will have greater droughtsdroughts

Effects of Global Climate Effects of Global Climate Change: Effects on OrganismsChange: Effects on Organisms

Zooplankton in parts of California Zooplankton in parts of California Current have decreased by 80% since Current have decreased by 80% since 19511951 Effecting entire food chainEffecting entire food chain

Decline in krill around AntarcticaDecline in krill around Antarctica Species have shifted their geographic Species have shifted their geographic

rangerange Migrating birds are returning to Migrating birds are returning to

summer homes earliersummer homes earlier

Effects on Organisms: Coral Effects on Organisms: Coral ReefsReefs Coral reefs can be bleached (right) Coral reefs can be bleached (right)

due to increase in water temperaturedue to increase in water temperature Affects coral symbiotes and makes them Affects coral symbiotes and makes them

more susceptible to diseasesmore susceptible to diseases

Effect on Organisms: Effect on Organisms: VegetationVegetation

Effect on Organisms: Effect on Organisms: VegetationVegetation

Effects on Human HealthEffects on Human Health Increased number of heat-related Increased number of heat-related

illnesses and deathsillnesses and deaths

Effects on AgricultureEffects on Agriculture Difficult to anticipateDifficult to anticipate

Productivity will increase in some areas and Productivity will increase in some areas and decrease in othersdecrease in others

Rise in sea level will inundate flood plains Rise in sea level will inundate flood plains and river valleys (lush farmland)and river valleys (lush farmland)

Effect on pests is unknownEffect on pests is unknown Warmer temperatures will decrease soil Warmer temperatures will decrease soil

moisture- requiring more irrigationmoisture- requiring more irrigation Location (i.e. elevation and altitude) where Location (i.e. elevation and altitude) where

certain crops can be grown may have to certain crops can be grown may have to changechange

International Implications of International Implications of Climate ChangeClimate Change Developed vs. Developed vs.

Developing Developing countriescountries Differing self-Differing self-

interestsinterests Differing Differing

ability to meet ability to meet the challenges the challenges of climate of climate changechange

Dealing with Global Climate Dealing with Global Climate ChangeChange

Two ways to manage climate changeTwo ways to manage climate change Mitigation: Limiting greenhouse gas Mitigation: Limiting greenhouse gas

emissions to moderate global climate emissions to moderate global climate changechange

Adaptation: Learning to live with Adaptation: Learning to live with environmental changes and societal environmental changes and societal consequences brought about by global consequences brought about by global climate change climate change

Relationship Between Relationship Between Mitigation and AdaptationMitigation and Adaptation

Dealing with Global Climate Dealing with Global Climate Change: MitigationChange: Mitigation

Locate/invent alternative fuels to Locate/invent alternative fuels to fossil fuelsfossil fuels

Increase efficiency of cars and trucksIncrease efficiency of cars and trucks Carbon Capture and StorageCarbon Capture and Storage Plant and Maintain trees to naturally Plant and Maintain trees to naturally

sequester carbonsequester carbon

Dealing with Global Climate Dealing with Global Climate Change: AdaptationChange: Adaptation Rising sea levels and coastal Rising sea levels and coastal

populationspopulations Move inlandMove inland Construct dikes and leveesConstruct dikes and levees

Adapt to shifting agricultural zonesAdapt to shifting agricultural zones NYC sewer lineNYC sewer line

International Efforts to International Efforts to Reduce Greenhouse Gas Reduce Greenhouse Gas EmissionEmission Kyoto ProtocolKyoto Protocol

Legally bindingLegally binding Provides operational rules on reducing Provides operational rules on reducing

greenhouse gasesgreenhouse gases US and Australia have not sign it - it will US and Australia have not sign it - it will

be difficult to implement without US be difficult to implement without US backingbacking