Chapter 18
GLOBAL CLIMATE CHANGE
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
change
• 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 4°C -- 7°C 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 Greenland
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://www.amazon.com
Overview
• 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 a
global 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 Speleothems
• Type of mineral formation which can be found in
caves
• The precipitation of calcium carbonate by groundwater
• 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
record
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://en.wikipedia.org
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 Earth’s 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
Earth’s Energy Balance (1)
Greenhouse
Earth’s Energy Balance (2)
• Greenhouse gases are actually needed to keep the Earth
warm. Without the greenhouse effect the water on the
Earth’s 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 wavelengths
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 concentrations
Global Temperature Change (1)
• The Pleistocene Ice Age: ~ 2 MYA, “Beginning of the
Ice Age”
• Numerous changes in Earth’s 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 .8°C (1.36°F) 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 Earth’s orbit around
the Sun (100,000 year cycles)
• Short cycle: The wobble effect of Earth’s 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 variables—solar, volcanic, and
anthropogenic gases
• 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://en.wikipedia.org/
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://en.wikipedia.org/
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 anthropogenic
forcing: 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:
http://www.pbs.org/wgbh/nova/sun/
Potential Effects of Global Climate (1)
• Doubling the greenhouse gases, then 1.5–6°C
(2.6−10.2°F) increase in average global temp
• Significant rise of sea level and melting of glacier
ice 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
Migrating sand dunes
Sahara Desert
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 developments
along 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 developing
countries 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