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Chapter 18

Weather Vs. Climate
  • Weather Short term variations in the atmosphere
    phenomena that interact and affect the
    environment and life
  • Climate The long-term average of variation in
    weather for a particular area

What is Global Climate Change?
  • Global climate (temperature) is changing and
    humans are influencing the change in climate
  • Global climate has changed in the geological
    past, various factors influence global climate
  • Climate will probably change in the future too

Past Global Climate Change (1A)
  • Medieval Warming Period (1100 A.D. 1300 A.D.)
  • Global climate was relatively warm
  • Glaciers receded in many parts of the world
  • Sea temperature 4C -- 7C warmer than it is now
  • Allowed people to settle into colder regions and
    navigate waters that were normally hazardous due
    to icebergs

Past Global Climate Change (1B)
  • During the Medieval Warming Period, the Vikings
    colonized Greenland
  • It is suspected that the waters were much warmer
    and the climate was warmer than in current

Sea routes of the Vikings
Artists conception of the Viking explorers
Past Global Climate Change (2A)
  • After the end of they Medieval Warming Period,
    scientists and historians now know that the
    Little Ice Age took place
  • Very cold winters existed and greatly affected
    Europe (around 1400)
  • Other conditions that persisted during the Little
    Ice Age included severe storms, wet periods, dry
    periods, extreme hot and cold conditions
  • Viking settlements abandoned in
  • Greenland

Little Ice Age in Spain ?
Past Global Climate Change (2B)
  • Good book to check out
  • Discusses how humans
  • adjusted to climatic changes
  • during the Little Ice Age
  • History of Europe a result of climate?

"Climate change is the ignored player on the
historical stage," writes archeologist Brian
Fagan. But it shouldn't be, not if we know what's
good for us. We can't judge what future climate
change will mean unless we know something about
its effects in the past "those who do not learn
from history are doomed to repeat it". And
Fagan's story of the last thousand years,
centered on the "Little Ice Age," reminds us of
what we could end up repeating flood, fire, and
famine--acts of God exacerbated by acts of man.
-Comment in a book review from http//
Climate changes Contributing to the complex evolutionary history of the Earth system Earth system Interactions between the atmosphere, the oceans, solid Earth, and the biosphere, Earth System Science a big component of studying global climate change The effects of human activities Extensive on aglobal scale
Tools for Studying Global Change (1A)
Uses of the geologic records to study climate Fossils, sediments, and rocks can tell the story about how environments have changed over time Using various dating techniques, the fossils, sediments, or rocks can be dated Ice cores e.g., carbon dioxide concentration in glacial ice (pockets of air preserved when the snow falls) Ocean sediment cores, also contain information about global climate change (small microorganisms that thrive in certain temperature conditions) Lake sediment cores, varves
Tools for Studying Global Change (1B)
  • Glacial tillite Glacial till lithified to rock
  • Evidence of ice age
  • Precambrian Gowganda Formation of Ontario, Canada
    (can be found in glacial drift in Ohio too)

Angular rocks surrounded by fine-grained
matrix (diamictite)
Tools for Studying Global Change (1C)
  • Deep ocean sediment core
  • Organic and inorganic
  • materials from the ocean can
  • be used to study past
  • environmental conditions
  • and past climates
  • Ocean Drilling Program
  • (ODP)

Scientists inspecting an ocean sediment core
Tools for Studying Global Change (1D)
  • Ice cores, studying trapped air pockets in ice
  • Ice caps, alpine glaciers, other places

Tools for Studying Global Change (1E)
  • Varves, layers that are deposited in a water
    environment (such as a lake)
  • If the layers in the varve deposited are annual,
    then they can be used to reconstruct the climate
  • Glacial lake varves

Tools for Studying Global Change (1F)
  • Carbonates can include something called
  • Type of mineral formation which can be found in
  • The precipitation of calcium carbonate by
  • Can be dated via radiometric dating (U)
  • Increased movement of GW thicker
  • layers
  • Decreased movement of GW thinner
  • layers

Example of a speleothem ?
Tools for Studying Global Change (1G)
  • Dendochronology Study of tree rings, tree rings
    can be used to date archaeological sites and
    certain climatic events
  • Wet year thick ring
  • Dry year thin ring
  • Only works in certain
  • areas and with certain
  • trees

Tree rings ? (Notice that they are not all the
same thickness)
Tools for Studying Global Change (2)
  • Real-time monitoring Collecting data on a
    regular basis in order to better understand and
    keep track of climatic changes
  • (1) Temperature
  • (2) Concentrations of atmospheric gases
  • (3) Composition of the ocean
  • (4) Other variables
  • Collecting data is necessary to track climatic
    trends and to calibrate data from the geological

Tools for Studying Global Change (3A)
  • Mathematical models Numerical means to
    represent real-world phenomena and the linkages
    and interactions between the processes involved
  • Used to solve complex problems
  • Help to understand atmospheric circulation and
    groundwater movement (among other things)
  • e.g., global circulation models (GCMs)

Tools for Studying Global Change (3B)
  • Diagram showing
  • how a GCM is used
  • data for each cell is
  • input into a computer
  • program and then
  • analysis is done using
  • a supercomputer
  • - Weather and climate
  • modeling

What is Climate?
  • Weather and climate are often confused
  • Weather is a term that encompasses phenomena in
    the atmosphere of a planet. The term is normally
    taken to mean the activity of these phenomena
    over short periods of time, usually no more than
    a few days.
  • Climate The statistical properties of the
    atmosphere, including measures of average
    conditions, variability, etc. (Over a period of
    time longer than days or weeks, usually seasons
    to decades.)
  • Understanding climate can be very complex
    (processes between all of the earth spheres.)

Taken from http//
Characteristic temperature and
precipitation conditions ?
Atmosphere and Climate Change
Climate change Change of atmosphere conditions and its relationships with lithosphere, hydrosphere, and biosphere Atmosphere as a complex chemical factory With many little-understood chemical reactions Changes in greenhouse gases, variable temp, and water vapor - Greatest variable within the Earths atmosphere is the concentration of water vapor

Global Warming
Temp of the Earth Three factors (1) The amount of sunlight received (2) The amount of solar energy reflected and absorbed (3) The amount of retention by atmosphere Earth Absorbing the short wavelength solar energy, then radiating long wavelength IR radiation Global warming Greenhouse effect
Earths Energy Balance (1)
Earths Energy Balance (2)
  • Greenhouse gases are actually needed to keep the
    Earth warm. Without the greenhouse effect the
    water on the Earths surface would be frozen.
    Earth would be a very cold place!
  • However, excessive greenhouse gases
  • could potentially warm the Earth too much
  • Venus runaway greenhouse effect

The planet Venus ?
The Greenhouse Effect (1)
Several atmospheric gases CO2, CH4, CFCs, nitrogen oxides trapping more heat and warming up the lower atmosphere, similar to the effect of a greenhouse The concentration of greenhouse gases increased recently due to human activities, anthropogenic gases (especially burning fossil fuels) Natural greenhouse warming occurs, water vapor the main culprit
The Greenhouse Effect (2)

The Greenhouse Effect (3)
Incoming infrared radiation has short wavelengths
but the outgoing infrared radiation has longer
Carbon Dioxide in the Atmosphere (1)

-Cycles of carbon dioxide are seasonal, more CO2
is taken out of the atmosphere during the
summer growing season in the northern Hemisphere.
-Most of the vegetation is located in the
northern hemisphere
Figure 18.8C
Carbon Dioxide in the Atmosphere (2)
Exponential growth in CO2 concentrations
-Low CO2 concentrations glacial episodes -High
CO2 concentrations interglacials
-CO2 concentrations over the past 160,000
years -Note the swift upward trend in CO2
Global Temperature Change (1)
The Pleistocene Ice Age 2 MYA, Beginning of the Ice Age Numerous changes in Earths mean annual temperature since then Warming trend over the last 150 years, especially since 1940s with the warmest in 1980s and 1990s Mean temp increased about .8C (1.36F) in the past 100 years
Global Temperature Change (2)
  • Climate has changed
  • numerous times
  • during the Pleistocene
  • -Glacials vs. interglacials
  • -Sea level going up and
  • down
  • -Greenhouse gases going
  • up and down

Why Climate Change?
Changes in long cycles (100,000 yrs) separated by short cycles (20,000 to 40,000 yrs) First identified in 1920s, Milankovitch hypothesis Long cycle The variability in Earths orbit aroundthe Sun (100,000 year cycles) Short cycle The wobble effect of Earths axis (20,000 / 40,000 year cycles)
Why Climate Change?
Climate system even unstable in shorter cycles, a few decades (not a few days as depicted by Hollywood) The ocean conveyor belt, global circulation of ocean water, contribute to the change Warm surface water is transported westward and northward (increasing in salinity owing to evaporation) to near Greenland, where it cools from contact with cold Canadian air. As the water increases in density, it sinks to the bottom and flows south, then east to the Pacific, where upwelling occurs. The masses of sinking and upwelling waters balance, and the total flow rate is about 20 million cubic meters (700 million cubic feet) per second. The heat released to the atmosphere from the warm water keeps northern Europe 5 degrees to 10 degrees C (8.5 degrees to 17 degrees F) warmer than it would be if the oceanic conveyor belt were not present Taken from Keller (2005)
Global Circulation of Ocean Water
  • Global warming Need to consider major forcing
    variablessolar, volcanic, and anthropogenic
  • Quite complicated to take all of these variables
    into consideration

Solar Forcing (1)
History of the past 1000 years Medieval warm period corresponding to a time increased solar radiation The little ice age (14th century) corresponding to the minimum solar activity
Solar Forcing (2)
  • Observation of sunspots for hundreds of years
  • Gives an idea of solar activity and how it has
    affected climate on Earth
  • Maunder Minimum occurred during the coldest part
    of the Little Ice Age

Coldest part of The Little Ice Age
  • Taken from http//

Solar Forcing (3)
  • Some scientists argue that the solar cycles
    affect climate more than greenhouse gas
    concentrations such as carbon dioxide
  • Controversial topic
  • Taken from http//

Volcanic Forcing (1)
Volcanic eruption Vast amount of aerosol particles into the air Aerosols Reducing solar radiation to the Earth surface, reflect incoming solar radiation Aerosols may have a counteracting effect on global warming Episodes of volcanic eruptions have significant contribution to the cooling of the Little Ice Age (pulse of volcanic eruptions
Volcanic Forcing (2)
  • Eruption of Mount Pinatubo
  • in the Philippines
  • Global climate was cooler
  • for several years after the
  • eruption

Eruption of Mount Pinatubo
Anthropogenic Forcing
Natural variability failing to explain the warming at end of the 20th century Mathematical modeling on the anthropogenicforcing Increase of temperature due to the doubling of CO2 Significant global warming as a result of human activities
Aerosols Causing Global Dimming (1)
  • Human processes could cause cooling too
  • Reflection from atmospheric particles could
    reduce incoming solar radiation by 10
  • Called global dimming

Aerosols Causing Global Dimming (2)
  • Good documentary movie to check out

Potential Effects of Global Climate (1)
Doubling the greenhouse gases, then 1.56C (2.6-10.2F) increase in average global temp Significant rise of sea level and melting of glacierice due to the increase in temp (affecting island nations most seriously, increased coastal erosion worldwide) The number of retreating glaciers accelerating in many areas of the world Some remote communities rely on glacial meltwater as a water supply
Potential Effects of Global Climate (2)
Global warming leads to significant changes of rainfall, soil moisture Agricultural activities and world food supplies affected greatly by climatic factors Global warming affects the frequency, intensity, and distribution of natural hazards, such as hurricane and other storms
Potential Effects of Global Climate (3)
  • Desertification
  • changing of
  • regional / global
  • climates
  • - Expanding deserts

Sahara Desert
Migrating sand dunes
Sahel Region
Sea Level Rise and Global Warming
An estimated 40 cm (16 in.) rise in sea level for the next century Increases in coastal erosion Up to 260 ft on open beaches Landward shift of existing estuaries Disastrous impact on the existing developmentsalong coastal zones
Biosphere and Global Warming
Causing a number of changes in biosphere, both people and overall ecosystem Risk of extinction due to land-use change and habitat shift Spread of infectious and other diseases due to migration of organisms
Increased El Nino Events
Reducing the Impact of GW (1)
(1) Identify the historic changes that have occurred (2) Predict the potential changes in the future (3) Reduce greenhouse gases (4) Political commitment Reconciling the conflicts between the environmental need for reduction of greenhouse gases and the economic demands for more fossil fuel
Reducing the Impact of GW (2)
Reduce the emission of CO2 Use fossil fuels releasing less CO2 Conservation of energy Store CO2 in forests, soils and rocks (sequestration of CO2) Use alternative energy
Coupling of Global Change Processes
The coupling of the greenhouse and ozone depletion problems from CFCs Burning of fossil fuels and acid rain problems Use of fossil fuels and volcanic eruptions problems and atmospheric cooling Emphasis on the principle of global environmental unity in action
Applied and Critical Thinking Topics
Rapid economic development in developingcountries occurs at the expense of environment. Should people put environment first? Why or why not? What can individual citizens do to help battle the global warming problem? Will new technologies be part of solution on problem in global warming? Explain
End of Chapter 18
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