Chapter 23: Global Change in the Earth System Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak Chapter 23 Global Change in the Earth System

Chapter 23: Global Change in the Earth System Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak

Chapter 23Global Change in the Earth System

©2008 W. W. Norton & Company, Inc.

Portrait of a PlanetThird Edition

earthearth

LECTURE OUTLINE

Global Change in the Earth SystemGlobal Change in the Earth System

Prepared by

Ronald ParkerEarlham College Department of Geosciences

Richmond, Indiana

Prepared by

Ronald ParkerEarlham College Department of Geosciences

Richmond, Indiana


Global ChangeGlobal Change Geology verifies that the Earth constantly changes. Geology verifies that the Earth constantly changes. Why does it constantly change?Why does it constantly change?

A plastic asthenosphere permits tectonic plate motion. A plastic asthenosphere permits tectonic plate motion. A star is close enough to warm Earth and its atmosphere.A star is close enough to warm Earth and its atmosphere. Temp. permits liquid water, thus, weathering and erosion.Temp. permits liquid water, thus, weathering and erosion. Biotic evolution has transformed the planet.Biotic evolution has transformed the planet.


The Goldilocks EffectThe Goldilocks Effect Venus is too close to the Sun.Venus is too close to the Sun.

No liquid water; no way to remove atmospheric CONo liquid water; no way to remove atmospheric CO22.. Runaway greenhouse conditions – Too hot for life.Runaway greenhouse conditions – Too hot for life.

Mars is too far from the Sun.Mars is too far from the Sun. All water is frozen.All water is frozen. No atmospheric CONo atmospheric CO22 to trap heat. to trap heat.

As in the story of Goldilocks, Earth is “just right.”As in the story of Goldilocks, Earth is “just right.”


The Earth SystemThe Earth System Life on Earth is due to interaction between the…Life on Earth is due to interaction between the…

Lithosphere.Lithosphere. Atmosphere. Atmosphere. Hydrosphere.Hydrosphere.

The “Earth System” is comprised of these physical The “Earth System” is comprised of these physical components interacting with the biosphere.components interacting with the biosphere.


The Earth SystemThe Earth System The interlinkage of the physical and the biological.The interlinkage of the physical and the biological. Global changes transform or modify both realms.Global changes transform or modify both realms.

There are many ways to describe changes.There are many ways to describe changes.Rate – Gradual vs. catastrophic.Rate – Gradual vs. catastrophic.Frequency – Unidirectional vs. cyclic. Frequency – Unidirectional vs. cyclic. Agency – Geogenic vs. anthropogenic.Agency – Geogenic vs. anthropogenic.

Change occurs in both a unidirectional and a cyclic manner. Change occurs in both a unidirectional and a cyclic manner.


Unidirectional ChangesUnidirectional Changes Evolution of the solid Earth.Evolution of the solid Earth.

Planetesimal accretion.Planetesimal accretion. Melting and differentiation.Melting and differentiation.

Iron sank to the center.Iron sank to the center.Produced a layered Earth.Produced a layered Earth.

Iron alloy core.Iron alloy core. Rocky mantle.Rocky mantle.


Unidirectional ChangesUnidirectional Changes Evolution of the solid Earth.Evolution of the solid Earth.

Formation of the Moon.Formation of the Moon.Mars-sized proto-planet collides.Mars-sized proto-planet collides.Mantle blasted into space.Mantle blasted into space.Debris coalesces to form the Moon. Debris coalesces to form the Moon.


Unidirectional ChangesUnidirectional Changes Evolution of the atmosphere and oceans.Evolution of the atmosphere and oceans.

Volcanic gases created an early atmosphere.Volcanic gases created an early atmosphere. Liquid water condensed to form the oceans. Liquid water condensed to form the oceans.


Unidirectional ChangesUnidirectional Changes Evolution of the atmosphere and oceans.Evolution of the atmosphere and oceans.

Life appeared quickly on Earth, by 3.8 Ga. Life appeared quickly on Earth, by 3.8 Ga. Living organisms modified the entire surface of Earth.Living organisms modified the entire surface of Earth.

Changed the composition of the atmosphere.Changed the composition of the atmosphere.Altered the chemistry of the oceans.Altered the chemistry of the oceans.


Unidirectional ChangesUnidirectional Changes Evolution of life.Evolution of life.

Living organisms were entirely single-celled until ~ 700 Ma.Living organisms were entirely single-celled until ~ 700 Ma. Rapid diversification followed development of…Rapid diversification followed development of…

Aerobic, eukaryotic cells.Aerobic, eukaryotic cells.Multicellular organisms. Multicellular organisms.


Physical CyclesPhysical Cycles The supercontinent cycle.The supercontinent cycle.

Plate tectonics drives a dance of the continents.Plate tectonics drives a dance of the continents. Ocean basins open and close.Ocean basins open and close. Continental land masses collide and rift apart again.Continental land masses collide and rift apart again. Supercontinents (like Pangaea) have formed several times.Supercontinents (like Pangaea) have formed several times.


Physical CyclesPhysical Cycles The sea-level cycle – SL is geologically unstable.The sea-level cycle – SL is geologically unstable.

SL has gone up and down many times in Earth history.SL has gone up and down many times in Earth history. Transgression (SL rise): shorelines invade land. Transgression (SL rise): shorelines invade land. Regression (SL fall): land is re-exposed.Regression (SL fall): land is re-exposed. T–R cycles are bounded by unconformities. T–R cycles are bounded by unconformities.


Physical CyclesPhysical Cycles The sea-level cycle – SL is geologically unstable.The sea-level cycle – SL is geologically unstable.

SL has gone up and down many times in Earth history.SL has gone up and down many times in Earth history.


Physical CyclesPhysical Cycles The rock cycle –There are 3 types of rock.The rock cycle –There are 3 types of rock.

Igneous – Cooled from a melt.Igneous – Cooled from a melt. Sedimentary – Made of eroded particles.Sedimentary – Made of eroded particles. Metamorphic – Rocks altered by heat and pressure. Metamorphic – Rocks altered by heat and pressure.


Physical CyclesPhysical Cycles Contrary to popular belief, rocks are not permanent.Contrary to popular belief, rocks are not permanent.

One rock type may transform into any other type. One rock type may transform into any other type. Thus, the atoms in rocks are constantly being rearranged.Thus, the atoms in rocks are constantly being rearranged. Require long periods Require long periods

of time.of time.


Biogeochemical CyclesBiogeochemical Cycles Chemical fluxes between living and nonliving.Chemical fluxes between living and nonliving. Involve storage and transfer between reservoirs.Involve storage and transfer between reservoirs.

Nonliving reservoirs.Nonliving reservoirs.Atmosphere.Atmosphere.Lithosphere.Lithosphere.Hydrosphere.Hydrosphere.

Living reservoirs.Living reservoirs.All living organisms.All living organisms.

Microbes.Microbes. Plants.Plants. Animals.Animals.


Biogeochemical CyclesBiogeochemical Cycles Many chemical compounds engage in these cycles.Many chemical compounds engage in these cycles.

Some interactions are essential for life (Calcium).Some interactions are essential for life (Calcium). Some interactions are toxic (Mercury).Some interactions are toxic (Mercury). Some may be either, depending on amount (Molybdenum).Some may be either, depending on amount (Molybdenum).

Rates of transfer between reservoirs vary widely.Rates of transfer between reservoirs vary widely. Examples. Examples.

Carbon.Carbon. Nitrogen.Nitrogen. Sulfur.Sulfur. Metals.Metals. Trace elements.Trace elements.


Biogeochemical CyclesBiogeochemical Cycles The hydrologic cycle: The hydrologic cycle:

Water moves between biological and physical reservoirs.Water moves between biological and physical reservoirs.Biological.Biological.

All living organisms.All living organisms.

Physical.Physical. Oceans.Oceans. Atmosphere.Atmosphere. Surface water.Surface water. Ground water.Ground water. Glaciers.Glaciers. Soil moisture.Soil moisture.


The Carbon CycleThe Carbon Cycle A biogeochemical cycle that regulates climate. A biogeochemical cycle that regulates climate.

Volcanic COVolcanic CO22 adds carbon to the atmosphere. adds carbon to the atmosphere.

Atmospheric COAtmospheric CO22 is removed in several ways. is removed in several ways. It dissolves in water.It dissolves in water.

Carbonic acid.Carbonic acid. Bicarbonate.Bicarbonate.

Photosynthesis Photosynthesis

removes COremoves CO22..

Weathering.Weathering.


Carbon may be stored for long periods of time.Carbon may be stored for long periods of time. Limestones.Limestones. Fossil fuels (coal and oil).Fossil fuels (coal and oil). Organic shales.Organic shales. Methane hydrates. Methane hydrates.

The Carbon CycleThe Carbon Cycle


The Carbon CycleThe Carbon Cycle Carbon is returned to the atmosphere. Carbon is returned to the atmosphere.

Biotic respiration creates COBiotic respiration creates CO22 from organic matter. from organic matter.

Rapid oxidation (burning) of organic matter creates CORapid oxidation (burning) of organic matter creates CO22..

Metamorphism of carbonate rocks liberates COMetamorphism of carbonate rocks liberates CO22..

Degassing removes dissolved CODegassing removes dissolved CO2 2 from water. from water.


Global Climate ChangeGlobal Climate Change Earth’s climate changes over geologic time scales.Earth’s climate changes over geologic time scales.

Long-term climate change.Long-term climate change.Millions to 10s of millions of years in scale.Millions to 10s of millions of years in scale.

Short-term climate change.Short-term climate change.10s to 100s of thousands of years in scale.10s to 100s of thousands of years in scale.


Global Climate ChangeGlobal Climate Change Climate studies reveal our past, suggest our future.Climate studies reveal our past, suggest our future.

Kinds of climate changes.Kinds of climate changes. Rates at which these changes occur.Rates at which these changes occur. Effects of climate changes on Earth and its inhabitants.Effects of climate changes on Earth and its inhabitants.

Methods of study. Methods of study. Paleoclimates – Investigations of past climatic variation.Paleoclimates – Investigations of past climatic variation. Computer simulations – Modeling past and future changes.Computer simulations – Modeling past and future changes.


Global Climate ChangeGlobal Climate Change Paleoclimates – Past climates are indicated by Paleoclimates – Past climates are indicated by

datable Earth materials that are climate-sensitive.datable Earth materials that are climate-sensitive. Stratigraphic records – Sequences of rock strata.Stratigraphic records – Sequences of rock strata.

Depositional environments are often climate-sensitive.Depositional environments are often climate-sensitive. Coral reefs – Tropical marine.Coral reefs – Tropical marine. Glacial tills – Cold and continental.Glacial tills – Cold and continental.


Global Climate ChangeGlobal Climate Change Paleoclimatic evidence: Paleoclimatic evidence:

Paleontological – Faunal assemblages are climate-sensitive.Paleontological – Faunal assemblages are climate-sensitive.Assemblage changes record climatic shifts.Assemblage changes record climatic shifts.

Pollen in pond sediments.Pollen in pond sediments.Spruce (colder) vs. hemlock (warmer).Spruce (colder) vs. hemlock (warmer).Trees (colder, drier) vs. grasses (warmer, wetter).Trees (colder, drier) vs. grasses (warmer, wetter).


Global Climate ChangeGlobal Climate Change Paleoclimates: Paleoclimates:

Oxygen isotopes – 2 isotopes: Oxygen isotopes – 2 isotopes: 1616O and O and 1818O.O. 1616O water evaporates faster than O water evaporates faster than 1818O water.O water.During ice ages…During ice ages…

1616O in seawater evaporates faster.O in seawater evaporates faster. This water is trapped on land as ice.This water is trapped on land as ice. Seas become Seas become 1616O depleted, O depleted, 1818O enriched.O enriched. 1818O/O/1616O increases.O increases.

During interglacials…During interglacials… Melting ice returns water to oceans.Melting ice returns water to oceans. 1616O returns to oceans.O returns to oceans. 1818O/O/1616O decreases.O decreases.

Ice core Ice core 1818O/O/1616O data track climate O data track climate

over 400 Ka.over 400 Ka.



Oxygen isotope ratios are preserved in carbonate shells.Oxygen isotope ratios are preserved in carbonate shells.The oxygen in CaThe oxygen in CaCOCO33 shells mirrors oceanic shells mirrors oceanic 1818O/O/1616O.O.

Changes in ocean chemistry are preserved in sea floor strata.Changes in ocean chemistry are preserved in sea floor strata.



Bubbles in ice – Tiny air pockets trapped in glacial ice.Bubbles in ice – Tiny air pockets trapped in glacial ice.Form at the time the snow turns to ice.Form at the time the snow turns to ice.Analysis of trapped air reveals atmospheric chemistry.Analysis of trapped air reveals atmospheric chemistry.Changes with depth in ice = changes over time.Changes with depth in ice = changes over time.



Growth rings – Tree rings can easily be dated.Growth rings – Tree rings can easily be dated.Ring thickness reflects climatic changes.Ring thickness reflects climatic changes.

Wetter, warmer = thicker; drier, colder = thinner.Wetter, warmer = thicker; drier, colder = thinner.

Ring widths form time sequences.Ring widths form time sequences.Overlapping sequences yield a time scale.Overlapping sequences yield a time scale.



Human history – Climatic changes recorded by people. Human history – Climatic changes recorded by people. Written history.Written history.Art history.Art history.Archaeological history.Archaeological history.


Long-Term Climate ChangeLong-Term Climate Change Global climate history has been Global climate history has been

largely deciphered.largely deciphered. Greenhouse – Warmer climates.Greenhouse – Warmer climates. Icehouse – Colder climates.Icehouse – Colder climates.

Last 100 million years.Last 100 million years. Warm climate at the end of Mesozoic.Warm climate at the end of Mesozoic. Climate cooling since Oligocene.Climate cooling since Oligocene.


Long-Term Climate ChangeLong-Term Climate Change What causes long-term climate changes? What causes long-term climate changes? Complex interactions across the Earth system. Complex interactions across the Earth system.

Plate tectonics modifies the position of continents.Plate tectonics modifies the position of continents.Oceanic currents – Closing the Isthmus of Panama.Oceanic currents – Closing the Isthmus of Panama.Determines locations that are high or low.Determines locations that are high or low.


Long-Term Climate ChangeLong-Term Climate Change What causes long-term climate changes? What causes long-term climate changes?

Volcanic gases trap heat, promote global warming.Volcanic gases trap heat, promote global warming.Mid-Cretaceous rifting and expanded mid-ocean ridges.Mid-Cretaceous rifting and expanded mid-ocean ridges.

Orogenic uplift consumes COOrogenic uplift consumes CO22 in rock weathering. in rock weathering.Leads to overall climatic cooling.Leads to overall climatic cooling.Uplift of the Himalayas attended Cenozoic cooling.Uplift of the Himalayas attended Cenozoic cooling.


Long-Term Climate ChangeLong-Term Climate Change What causes long-term climate changes? What causes long-term climate changes?

Biological influences.Biological influences.Formation of organic deposits removes COFormation of organic deposits removes CO22..

Coal.Coal. Oil.Oil. Natural gas.Natural gas.

Evolution. Evolution. Appearance of lichens in the Neoproterozoic.Appearance of lichens in the Neoproterozoic. Appearance of grasses in the Miocene.Appearance of grasses in the Miocene.


Long-Term Climate ChangeLong-Term Climate Change COCO22 and CH and CH44 are greenhouse gases. are greenhouse gases.

Transparent to incoming UV radiation from the Sun.Transparent to incoming UV radiation from the Sun. Absorb infrared energy re-emitted from Earth’s surface.Absorb infrared energy re-emitted from Earth’s surface.

Greenhouse gases exert a strong control on climate.Greenhouse gases exert a strong control on climate. More GHG – Warmer; Less GHG – Cooler. More GHG – Warmer; Less GHG – Cooler.

Processes that add or remove GHGs alter climate.Processes that add or remove GHGs alter climate.


Short-Term Climate ChangeShort-Term Climate Change The past million years – Dramatic climate flux.The past million years – Dramatic climate flux.

5 major glaciations.5 major glaciations. 20 to 30 minor glaciations.20 to 30 minor glaciations. Separated by interglacials.Separated by interglacials.

Warmer or colder climates may last 1,000s of years.Warmer or colder climates may last 1,000s of years. Climate shifts may occur in as little as a decade.Climate shifts may occur in as little as a decade.


The past 15,000 years (the Holocene).The past 15,000 years (the Holocene). Warming led to deglaciation, yet temps still fluctuate.Warming led to deglaciation, yet temps still fluctuate. Several cold periods have punctuated this interglacial.Several cold periods have punctuated this interglacial.

Younger Dryas.Younger Dryas.Holocene maximum.Holocene maximum.Medieval warm period.Medieval warm period.Little ice age.Little ice age.Modern warming trend.Modern warming trend.

Short-Term Climate ChangeShort-Term Climate Change


Short-Term Climate ChangeShort-Term Climate Change Fluctuations in solar and cosmic radiation.Fluctuations in solar and cosmic radiation.

Solar output varies with the sunspot cycle.Solar output varies with the sunspot cycle.Sunspot activity spikes every 9 to 11.5 years.Sunspot activity spikes every 9 to 11.5 years. Increased sunspots attend a decrease in solar output.Increased sunspots attend a decrease in solar output.

Changes in the natural cosmic radiation flux…Changes in the natural cosmic radiation flux…May cool Earth by increasing high-altitude clouds.May cool Earth by increasing high-altitude clouds.May warm the Earth by increasing low-altitude clouds. May warm the Earth by increasing low-altitude clouds.


Short-Term Climate ChangeShort-Term Climate Change Changes in Earth’s orbit and tilt.Changes in Earth’s orbit and tilt.

Milankovitch factors. Milankovitch factors. Earth’s axis wobbles (precession).Earth’s axis wobbles (precession).

23,000-year periodicity.23,000-year periodicity.

Angle of axis (obliquity) changes. Angle of axis (obliquity) changes. 41,000-year periodicity.41,000-year periodicity.

Shape (eccentricity) of orbit varies.Shape (eccentricity) of orbit varies. 100,000-year periodicity.100,000-year periodicity.

These factors alter insolation.These factors alter insolation.


Short-Term Climate ChangeShort-Term Climate Change Changes in volcanic emissions.Changes in volcanic emissions.

Atmospheric reflectivity due to clouds (albedo) varies.Atmospheric reflectivity due to clouds (albedo) varies. Volcanic aerosols significantly contribute to albedo.Volcanic aerosols significantly contribute to albedo.

Tambora (1815) resulted in the “year without a summer.”Tambora (1815) resulted in the “year without a summer.”


Short-Term Climate ChangeShort-Term Climate Change Changes in oceanic currents.Changes in oceanic currents.

Ocean currents distribute equatorial heat to the poles. Ocean currents distribute equatorial heat to the poles. Disruption of currents could initiate cooling.Disruption of currents could initiate cooling.

Currents are driven by thermohaline sinking at the poles.Currents are driven by thermohaline sinking at the poles.Melting sea ice could alter the salt-density underflow. Melting sea ice could alter the salt-density underflow.


Short-Term Climate ChangeShort-Term Climate Change Global changes in greenhouse gas concentrations.Global changes in greenhouse gas concentrations.

Sudden addition or removal of GHGs could alter climate.Sudden addition or removal of GHGs could alter climate.Sudden release of methane hydrates from ocean sediments.Sudden release of methane hydrates from ocean sediments.Changes in the amount of photosynthesizers (algal blooms, Changes in the amount of photosynthesizers (algal blooms,

deforestation, etc.) could change COdeforestation, etc.) could change CO22 concentrations. concentrations.


Climate ChangeClimate Change Catastrophic events – Occur very rapidly.Catastrophic events – Occur very rapidly.

Local – Volcanic eruptions, earthquakes, tsunamis, etc.Local – Volcanic eruptions, earthquakes, tsunamis, etc. Global – Bolide impacts, flood basalts. Global – Bolide impacts, flood basalts.

Catastrophic events may induce mass extinctions.Catastrophic events may induce mass extinctions. K-T (Cretaceous – Tertiary) boundary event.K-T (Cretaceous – Tertiary) boundary event.

End Mesozoic extinction (dinosaurs and many others).End Mesozoic extinction (dinosaurs and many others).Coeval with an asteroid impact on the Yucatan peninsula.Coeval with an asteroid impact on the Yucatan peninsula.Debris from the Chicxulub impact may have blocked the Sun.Debris from the Chicxulub impact may have blocked the Sun.


Extinction events – The stratigraphic record contains Extinction events – The stratigraphic record contains evidence of dramatic decreases in biodiversity.evidence of dramatic decreases in biodiversity.

Large numbers of species disappear forever. Large numbers of species disappear forever. Major extinctions.Major extinctions.

Late Ordovician.Late Ordovician. Mid-Late Devonian.Mid-Late Devonian. End Permian.End Permian. Late Triassic.Late Triassic. End Cretaceous.End Cretaceous.

Climate ChangeClimate Change


Anthropogenic ChangesAnthropogenic Changes Prehistoric humans were few having a small impact.Prehistoric humans were few having a small impact. Today, humans are a huge force of planetary change.Today, humans are a huge force of planetary change.

Exponential population growth aided by revolutions in...Exponential population growth aided by revolutions in... Industry, agriculture, technology, and medicine fueled by...Industry, agriculture, technology, and medicine fueled by... A suitable supply of natural resources.A suitable supply of natural resources.

Humans may rival or exceed some natural Humans may rival or exceed some natural processes.processes.


Anthropogenic ChangesAnthropogenic Changes Landscape modifications.Landscape modifications.

Human-induced erosion may exceed natural processes.Human-induced erosion may exceed natural processes.


Anthropogenic ChangesAnthropogenic Changes Ecosystem modification – Balances are destabilized.Ecosystem modification – Balances are destabilized.

Human changes occur faster than organisms can adapt.Human changes occur faster than organisms can adapt. Rainforest decline is largely the result of human agency.Rainforest decline is largely the result of human agency.


Anthropogenic ChangesAnthropogenic Changes Ecosystem modifications – Destroy habitats.Ecosystem modifications – Destroy habitats.

Deforestation.Deforestation. Overgrazing.Overgrazing. AgricultureAgriculture Urbanization.Urbanization.


Anthropogenic ChangesAnthropogenic Changes Pollution – Materials that are in the wrong place. Pollution – Materials that are in the wrong place. Modern human society generates contaminants.Modern human society generates contaminants.

Solid, liquid or gaseous materials that overwhelm natural Solid, liquid or gaseous materials that overwhelm natural attenuation mechanisms and degrade their locales. attenuation mechanisms and degrade their locales.

Contaminating materials are diverse.Contaminating materials are diverse.


Anthropogenic ChangesAnthropogenic Changes Pollution – Air quality.Pollution – Air quality.

Smog (smoke + fog) – Urban haze created by reaction of…Smog (smoke + fog) – Urban haze created by reaction of…Ground-level ozone, and…Ground-level ozone, and…Unburned hydrocarbons.Unburned hydrocarbons.Catalyzed by sunlight.Catalyzed by sunlight.


Anthropogenic ChangesAnthropogenic Changes Pollution – Water contamination.Pollution – Water contamination.

Pollutants frequently enter surface water and groundwater.Pollutants frequently enter surface water and groundwater.Sanitary wastes.Sanitary wastes.Fuel and oil.Fuel and oil.Solvents.Solvents.Fertilizers.Fertilizers.Pesticides.Pesticides.


Anthropogenic ChangesAnthropogenic Changes Pollution – Acidification.Pollution – Acidification.

Acid runoff – Sulfide mineral oxidation releases acid.Acid runoff – Sulfide mineral oxidation releases acid.Coal mining.Coal mining.Base metal mining.Base metal mining.

Acid rain – Sulfate-rich aerosols Acid rain – Sulfate-rich aerosols

acidify rain.acidify rain.Coal-fired power plants.Coal-fired power plants.


Anthropogenic ChangesAnthropogenic Changes Pollution – Radioactive waste.Pollution – Radioactive waste.

Nuclear materials mining and processing generate wastes.Nuclear materials mining and processing generate wastes.Mine spoil and mill tailings.Mine spoil and mill tailings.High-level nuclear wastes.High-level nuclear wastes.Medical radioactive isotopes.Medical radioactive isotopes.


Anthropogenic ChangesAnthropogenic Changes Pollution – Stratospheric ozone (OPollution – Stratospheric ozone (O33) depletion.) depletion.

Chlorofluorocarbons (CFCs) catalyze destruction of ozone.Chlorofluorocarbons (CFCs) catalyze destruction of ozone. Stratospheric ozone protects Earth from UV radiation.Stratospheric ozone protects Earth from UV radiation. Ozone depletion is potentially harmful to life. Ozone depletion is potentially harmful to life. Note: Ozone depletion is unrelated to CONote: Ozone depletion is unrelated to CO22 buildup. buildup.


Anthropogenic ChangesAnthropogenic Changes Are human GHG increases Are human GHG increases

causing global warming?causing global warming? Most scientists agree that the Most scientists agree that the

answer is “Yes!”answer is “Yes!” Human agency has greatly Human agency has greatly

increased COincreased CO22 and CH and CH44

concentrations.concentrations. The rate of addition jumps The rate of addition jumps

markedly at the start of the markedly at the start of the industrial revolution.industrial revolution.


Anthropogenic ChangesAnthropogenic Changes Human GHG increases ARE causing global warming.Human GHG increases ARE causing global warming.

COCO22 in the atmosphere has steadily climbed since 1958. in the atmosphere has steadily climbed since 1958.

In 1958, COIn 1958, CO22 was ~ 315 ppm; in 2000, CO was ~ 315 ppm; in 2000, CO22 was ~ 370 ppm. was ~ 370 ppm.

COCO22 varies seasonally by ~5 ppm due to plant activity. varies seasonally by ~5 ppm due to plant activity.


Anthropogenic ChangesAnthropogenic Changes Are human GHG increases causing global warming?Are human GHG increases causing global warming? Data amassed over 3 decades supports a “yes.”Data amassed over 3 decades supports a “yes.”

Disintegration of Antarctic ice shelves. Disintegration of Antarctic ice shelves.


Anthropogenic ChangesAnthropogenic Changes Melting of the Greenland ice Melting of the Greenland ice

sheet is accelerating.sheet is accelerating.


Anthropogenic ChangesAnthropogenic Changes

The sea ice covering the Arctic Ocean is shrinking.The sea ice covering the Arctic Ocean is shrinking.


Anthropogenic ChangesAnthropogenic Changes Valley glaciers are retreating rapidly worldwide.Valley glaciers are retreating rapidly worldwide. The sea ice covering the Arctic Ocean is shrinking.The sea ice covering the Arctic Ocean is shrinking.


Anthropogenic ChangesAnthropogenic Changes Maple sap runs earlier.Maple sap runs earlier. The mosquito line (elevation marking survival) has risen.The mosquito line (elevation marking survival) has risen. Polar bears are threatened by loss of pack ice for hunting.Polar bears are threatened by loss of pack ice for hunting. Area of permafrost has substantially decreased.Area of permafrost has substantially decreased.


Anthropogenic ChangesAnthropogenic Changes Intergovernmental Panel on Climate Change (IPCC).Intergovernmental Panel on Climate Change (IPCC).

Founded in 1988 by the United Nations.Founded in 1988 by the United Nations. Reviews climate science.Reviews climate science. Publishes an assessment of the science every 5 years. Publishes an assessment of the science every 5 years. Fourth Assessment Report (2007) indicated…Fourth Assessment Report (2007) indicated…

Climate warming is happening.Climate warming is happening.We know a lot more then we did a few years ago.We know a lot more then we did a few years ago.Humans are a substantial cause of warming.Humans are a substantial cause of warming.


Anthropogenic ChangesAnthropogenic Changes Most scientists accept global warming as fact. Most scientists accept global warming as fact. Fewer dispute warming as data accumulates.Fewer dispute warming as data accumulates.

Surface air temperatures have warmed by 0.9Surface air temperatures have warmed by 0.9ooC since 1880.C since 1880.


Anthropogenic ChangesAnthropogenic Changes Since 1920, global temperature has increased.Since 1920, global temperature has increased.

1900s warming has reversed a 1,000-year cooling trend.1900s warming has reversed a 1,000-year cooling trend.


Anthropogenic ChangesAnthropogenic Changes The global warming debate has largely shifted.The global warming debate has largely shifted.

From “if” warming is occurring, to the magnitude of effects.From “if” warming is occurring, to the magnitude of effects.

Computer models help to predict climate changes.Computer models help to predict climate changes. By 2050, average annual T will increase by 1.5By 2050, average annual T will increase by 1.5ooC to 2.0C to 2.0ooC.C. By 2150, global T may be 5By 2150, global T may be 5ooC to 11C to 11ooC warmer than present.C warmer than present.


Anthropogenic ChangesAnthropogenic Changes The predicted effects of global warming.The predicted effects of global warming.

A shift in climate belts.A shift in climate belts.Ecozones will shift toward poles.Ecozones will shift toward poles.Deserts will expand.Deserts will expand.Less soil may be fertile.Less soil may be fertile.



Stronger storms due to a more vigorous hydrologic cycle.Stronger storms due to a more vigorous hydrologic cycle.Higher sea surface temps.Higher sea surface temps.Greater evaporation.Greater evaporation.Greater differential pressures.Greater differential pressures.2005 set a number of storm records.2005 set a number of storm records.



A rise in sea level. A rise in sea level. Sea level is now rising 1-2 mm/year.Sea level is now rising 1-2 mm/year.Warming will accelerate this trend by…Warming will accelerate this trend by…

Thermal expansion of seawater.Thermal expansion of seawater. Melting polar ice.Melting polar ice.



A rise in sea level. A rise in sea level. Many people live within a meter of SL.Many people live within a meter of SL.Rising SL will displace millions.Rising SL will displace millions.


Anthropogenic ChangesAnthropogenic Changes Many scientists think that warming might lead to…Many scientists think that warming might lead to…

Interruption of the oceanic circulation system. Interruption of the oceanic circulation system. Warm water moves poleward to replace polar deep water.Warm water moves poleward to replace polar deep water. Disrupting the fall of polar water may idle warm return flow.Disrupting the fall of polar water may idle warm return flow.


Earth’s FutureEarth’s Future Our future on Earth requires sustainable growth.Our future on Earth requires sustainable growth.

Prosperity based on balancing societal and human needs.Prosperity based on balancing societal and human needs.The limitations of Earth’s finite resources. The limitations of Earth’s finite resources.

Without sustainability, humans will be in trouble. Without sustainability, humans will be in trouble. Earth system disruption will reach a critical point based on... Earth system disruption will reach a critical point based on...

Natural resource limitations (fuels, metals, water).Natural resource limitations (fuels, metals, water). Shrinking land areas.Shrinking land areas. Increasing populations.Increasing populations.

Under such a scenario, Earth will dictate a new equilibrium.Under such a scenario, Earth will dictate a new equilibrium.


Earth’s FutureEarth’s Future In millions of years, Earth’s surface will differ.In millions of years, Earth’s surface will differ.

Plate tectonic will reshuffle continents.Plate tectonic will reshuffle continents. Erosion will reshape the landscape.Erosion will reshape the landscape. Seas will invade or expose land.Seas will invade or expose land.

Homo sapiensHomo sapiens is not likely to remain. Our options? is not likely to remain. Our options? Extinction.Extinction. Evolution.Evolution.


Earth’s FutureEarth’s Future In billions of years, Earth will be vaporized.In billions of years, Earth will be vaporized.

The Sun will run out of hydrogen.The Sun will run out of hydrogen. It will collapse inward.It will collapse inward. Collapse will heat it.Collapse will heat it. It will expand outward.It will expand outward. The red giant phase of The red giant phase of

the Sun will expand the Sun will expand

past the orbit of Earth.past the orbit of Earth. Earth will vaporize.Earth will vaporize. C’est la vie!C’est la vie!


Chapter 23Global Change in the Earth System

©2008 W. W. Norton & Company, Inc.

Portrait of a PlanetThird Edition

earthearth

LECTURE OUTLINE

This concludes the

Documents

Chapter 23: Global Change in the Earth System Earth: Portrait of a Planet, 3 rd edition, by Stephen Marshak Chapter 23 Global Change in the Earth System