Lecture 6: Climate Change, Volume 1

1
Lecture 6 Climate Change, Volume 1

• Earths Climate Variability and
• Reconstructing Previous Climates

2
Lecture 6, Volume 1 Outline

• Earths Climate Variability
• Factors That Affect Earths Climate
• Ways of Measuring Past Climates

3
Global Temperature and Precipitation Change
over Geologic Time
This graph is the estimated global climate over
the Phanerozoic. The Red line represents Modern
temp/precip.
Condie and Sloan, 1998
4
From the previous slide

• Note the following
• Since the formation of Earth, global climate has
  generally cooled
• There are several instances where the Earths
  climate was warmer than today, such as during the
  Mesozoic and early Cenozoic.
• There are several instances when the Earths
  climate was cooler than today, such as during the
  Ordovician, Permian, and most of the Quaternary

5
Global Temperature Change Over Time
A) 180 MYBP - Present
Isotope Substation 5e
B) 1 MYPB - Present
Mackensie (1999), Our Changing Planet
6
The Quaternary

• Note that the Quaternary (last 1.8 million years)
  is characterized by climatic oscillations. These
  oscillations occur about every 100,000 years, and
  they are divided into two stages
• Glacial stage when global climate is cooler
  lasting in duration for approximately 60,000
  90,000 years
• Interglacial stage when global climates are
  warmer lasting in duration for approximately
  40,000 years to 10,000 years.
• The most common glacial duration is 90,000 years
  in length and the most common interglacial
  duration is 10,000 years in length.

7
The Wisconsin Glaciation

• The most recent glaciation is the Wisconsin
  Glaciation
• Glaciers advanced across North America around
  120,000 years ago. The maximum extent of
  glaciers occurred around 18,000 years ago (The
  Wisconsin Glacial Maximum, WGM). This is the
  period during the most recent glaciation when
  global temperatures where at their coolest
  (estimates are between 4C to 8 C cooler than
  today). Since that time, global temperatures
  have warmed, although the warming trend has not
  been consistently linear. Several blips in the
  warming trend are apparent, such as during the
  Younger Dryas period, ca. 14,500 years ago.

8
Wisconsin Glaciation Ice Sheets
Berengia Land Bridge
Laurentide
Cordilleran
http//academic.emporia.edu/aberjame/ice/lec01/ice
gl2.gif
9
Ruddiman (2001) Earths Climate Past and Future
(pg. 303).
10
H
Polar Jet
11
Global Temperature Change Over Time
C) 100 K YR BP - Present
D) 18 K YR BP - Present
Mackensie (1999), Our Changing Planet
12
Holocene

• The last 10,000 years are characterized as the
  Holocene, the current interglacial period. The
  Holocene has climatic oscillations embedded
  within the overall warming period.
• The Climatic Optimum (or Hypsothermal) was a time
  when global temperatures were ca. 4 warmer than
  today.
• During 1000 AD, temperatures where again warmer
  than today. We know this from historical records
  of vineyards in England, Vikings colonizing
  Greenland, etc..
• From 1300 mid 1800s climate in the Northern
  Hemisphere was colder than present. This time
  period is called the Little Ice Age

13
Warming trend
LIA
Note the warming trend after the Little Ice Age
(LIA)
Mackensie (1999), Our Changing Planet
14
Glacial Retreat in the French Alps following the
Little Ice Age
Glaciers advanced during the Little Ice Age in
the Alps.
Glacier
1850 AD
1966 AD
Kump et al. (1999), The Earth System
15
Synopsis of the last few slides

• The Earths climate is variable.
• Currently we are in an interglacial cycle when
  temperatures are abnormally warmer than the
  Quaternary average
• The interglacial cycles in the past have lasted
  10,000 years, the current interglacial is 10,000
  years in age.
• Theoretically if the same processes that have
  been going on for the last 1.8 million years are
  still present (glacial/interglacial cycles), then
  by all accounts the next ice age should begin
  anytime now.
• The climate over the last decade is warmer than
  it has been throughout the early Twentieth
  Century.

16
What causes changes in global climate

• Plate Tectonics The ocean currents redistribute
  heat on the planet. The current continental
  arrangement allows warm ocean currents (e.g. the
  Gulf Stream) to carry warm tropical waters to the
  polar regions and cool ocean currents (e.g. the
  California current) to carry cooler polar waters
  towards the tropics. This is possible because
  the continents are aligned in north-south
  orientation. When continents shift, as in the
  breakup of Pangaea, this poleward heat transfer
  is blocked. The absence of warm waters moving to
  the north is believed to instigate ice ages (like
  that in the Permian).

17
The Major Surface Ocean Currents Today
Continental arrangements are North - South
(McKnight, 1999)
18
Note how the position of the continents
interferes with the poleward heat transfer
The Breakup of Pangaea
(McKnight, 1999)
19
Changes in Solar Insolation

• Variations in the Earths orbit affect the amount
  of sunlight. This is explained by the
  Milankovich cycles. I believe that you have had
  this in Geology 2 (according to Ms. Ruffin you
  remember her from the orientation DVD, she
  teaches a few TIG classes). Just as a review,
  Milankovitch describes three orbital changes
• Eccentricity earth changes from circle to
  elliptical orbit -100,000 yr cycle
• Tilt the Earths tilt wobbles from 21.5 to
  24.5 every 40,000 yrs.
• Precession of the seasons, change in the
  direction the axis is pointing 20,000 yr cycle.
  
• All these orbital changes affect solar
  insolation, which is related to changes in global
  climate

20
Milankovitch Cycle
Kump et al. (1999)
21
Atmospheric Gasses

• Certain gasses in the atmosphere trap terrestrial
  radiation, analogous to a blanket.
• CO2 especially
• Review the Global Energy Balance and pay
  attention to the interaction of long-wave
  radiation and the atmosphere.
• Theoretically by increasing or decreasing the
  concentration of greenhouse gasses will result in
  trapping more terrestrial heat or allowing more
  heat to escape to outer space, respectively.
  Thus the concentration of CO2 (and other gasses)
  affects global temperature.
• From your textbook.

22
Figure 20-3
23
Current Warming Trend

• It is believed by many (and refuted by many) that
  the recent warming trend is related to an
  increase in CO2 following the Industrial
  Revolution.

24
Ways to Measure Previous Climates

• Oxygen Isotope From Ice cores, cooler climates
  will have the lighter oxygen isotope (O16) in
  more abundance than the heavier O18. When its
  cooler, the lighter oxygen is evaporated
  preferentially the heavier oxygen stays in the
  oceans.
• Marine sediments show the opposite trend.
• Ice cores also trap minute gas bubbles. The gas
  bubbles can be used to measure the gas
  composition of the atmosphere when the ice layer
  was deposited.

25
Changes in the Oxygen isotopic Composition of
Seawater During the Growth of Continental Ice
Sheets
Kump et al. (1999)
26
Ice Core
www.homepage.montana.edu
27
Deep Sea Cores

• Evidence from the sediment cores (O18/O16 ratios
  in marine sediment) collected from the ocean
  depths reveal climate variability over the last
  700,000 years. This correlates nicely with
  climatic variability associated with Milankovich.

28
18O/16O Ratio from Deep-Sea Sediment Cores
Raymo (1994) Ann. Rev. of Earth Plan. Scil,
22353-383 taken from Kump et al. (1999), The
Earth System, pg 214
29
Vostok Ice Core

• Cores from Antarctica also show climatic
  variability. They also show a highly correlative
  relationship between CO2 concentration (from the
  gas bubbles in the ice core) and temperature
  (from O18/O16 ratio in the ice).

30
CO2 (a) and Global Temperatures (b) from the
Vostock Ice Core
Note the Correlation Of CO2 And temp.
From R.W. Christopherson, Geosystmes AN
Introduction to Physical Geography, 3/e, 1997.
Reprinted by permission of Prentice Hall, Upper
Saddle River, N.J.) taken from Kump et al.
(1999), pg 221.
31
Other Paleoclimate Methods

• Palynology the study of pollen. Pollen
  preserved in lake sediments (and other
  environments) is reflective of the vegetation
  around the lake when it was deposited.
  Determining the type and amount of each pollen
  type can allow scientists to determine vegetation
  changes, such as from forest to grassland or from
  tundra to forest.
• Vegetation is strongly linked to climate. So the
  fossil pollen grains are records of previous
  climates.

32
Various Pollen Types
Oak
Elm
Beech
Spruce
Bush (1999)
33
Sediment Core from Dukes Pond, GA
My Colleague Andrew Ivester (West Georgia
University) and I collecting Sediment cores for
pollen analysis in southeastern Georgia
Pollen is preserved in The anaerobic, mucky soils
modern
4000 years ago
34
Pollen Diagram for Silver Lake, Ohio
Mixed Deciduous Forest
Boreal forest
Note the change in pollen types around 12,000
years. What do you Think would be causing this
change? Retreat of the glaciers perhaps?
Bush (1999)
35
Dendrochronology

• The width of annual rings in trees are strongly
  reflective of the environment the tree is growing
  in.
• Note Trees in more marginal or stressful
  habitats are more sensitive to environmental
  ameliorations.
• Not all trees produce visible annual rings. Some
  wood types (hardwoods especially) have an
  abundance of a plant tissue called vessel
  members which obscure annual rings. Usually the
  conifers, which lack vessel members, have the
  clearest ring development.

36
Extruding core from borer
Me coring a tree on South Core Banks Island, NC.
I was much younger And enthusiastic back then!
37
Some trees are really old

• Trees out west can be very old. The bristle cone
  pine, for example, has a life span of several
  thousands of years.
• Tree rings from these old individuals can push
  the climatic record back to thousands of years.
• Dendrochonology is really cool because it allows
  you to see annual climatic changes. Pollen
  analysis on the other hand can go back further in
  time (last couple hundred thousands of years) but
  it has a very coarse resolution maybe the last
  50 or 100s of years get blended.

38
Bristlecone Pine - Oldest living tree, 4900 years
old
39
Conclusion of Volume 1

• The Earths climate is variable. I want you to
  be aware of how it varies because I believe that
  it will help you understand the current global
  warming debate.
• In discussing the future state of the planet, I
  believe that we must have a working knowledge of
  what has gone on in the past.
• From this part of the lecture I want you to be
  able to recognize important climatic time periods
  (Wisconsin Glacial Max, Holocene, Hypsothermal,
  Little Ice Age, etc.) understand the climatic
  oscillations that have occurred in the past and
  understand a little about how these climatic
  variations have been estimated.

40
Lecture 6 Climate Change, Volume 2

• Current Global Climate Change Debate

41
Lecture 6, Volume 2 Outline

• Current Trends
• Temperature
• Carbon Dioxide
• Consequences of a warmer planet
• Sea Level
• Hurricanes
• Uncertainties with feedback loops
• Government Panels on Climate Change
• Concluding Remarks

42
A set of temperature records from over 7,000
stations around the world has been compiled by
the NOAA National Climate Data Center to create
the Global Historical Climatology Network - GHCN
(GHCN Version 2 data set Peterson and Vose
1997). About 1,000 of these records extend back
into the 19th century.
http//www.ncdc.noaa.gov/paleo/globalwarming/instr
umental.html
43
Satellite Data from NOAA

• The current rate of warming is 0.06C per decade,
  which is slower than ground-based thermometers
  (NOAA, 2006). It is unclear why the satellite
  and ground thermometers show discrepancies.

http//www.ncdc.noaa.gov/paleo/globalwarming/instr
umental.html
44
Current Trends

• For the last 100 years or so global temperatures
  have warmed

http//www.ncdc.noaa.gov/img/climate/research/2005
/ann/global-blended-temp-pg.gif
45
Sea Surface Temperatures have also been rising
46
In addition to higher temperatures, the
atmospheric concentration of CO2 has also
increased in the last 100 years

• Current CO2 concentrations are

http//www.ngdc.noaa.gov/paleo/ctl/cliihis100.html
47
Cloud Cover has also increased
Northern Hemisphere during the past century
(Groisman, 1999). While water vapor is the most
abundant greenhouse gas, low clouds also shade
and cool the surface. Currently the role that
water vapor and clouds play in warming or
cooling the Earth's climate system is being
investigated.
http//www.ngdc.noaa.gov/paleo/ctl/cliihis100.html
48
Earths Climate is Changing?

• So there are signs that the global temperatures
  are warming, especially over the last 100 years.
  I dont think too many people would argue against
  that.
• Is this directly related to elevated atmospheric
  CO2? Are there feedback mechanisms to mitigate
  this?
• Is this part of a significant warming trend or is
  this just background noise in a complex time
  series?
• These are questions that are difficult to answer
  with any certainty, at least at this time.

49
What are the consequences of a warmer climate?

• The most noted global change from a warmer planet
  is a rise in sea level. Currently the global sea
  level is rising at a rate of 2mm/year.
• Sea level rises due to
• Glacio-Eustatic changes
• Thermal expansion
• Changes in ocean shape

50
Sea Level Rise, US Rates
Davis and Fitzgerald, 2002 Beaches and Coasts.
51
Ice Sheet

• The two large ice sheets, Greenland and
  Antarctica, contain enormous volumes of water.
  Should these glaciers melt, then sea level would
  rise.
• If Greenland melted sea level would rise by as
  much as 7 feet.
• IF Antarctica melted, sea level would rise by as
  much as 70 feet.

52
Greenland and Antarctica Ice

• Currently the Greenland Ice sheet is melting.
  The Jakobshavn Isbrae doubled its meltwater flow
  from 1997 2003, and this influx of meltwater
  has caused a measurable rise in sea level (The
  Heat is On, The Economist, Vol 380, No. 8494 pg
  9)
• The western Antarctic ice sheet, Larsen B, is
  also melting (The Economist article cited above).
• Will this trend continue? Is this part of a
  natural glacial cycle? Is this related to the
  current global warming trend? Should we be
  preemptive and purchase beach front property in
  Iowa? How much will this affect global sea
  level? There is still a large degree of
  uncertainty, more research is needed.
• In any event, with higher sea level countries
  such a Bangladesh, The Bahamas, and much of the
  Atlantic Seaboard and Gulf Coasts are in trouble.

53
Themohalocline Circulation

• Related to the melting of ice is the risk of
  interrupting the Thermohaline Circulation

54
Thermohaline Circulation
www.ncdc.noaa.gov/paleo/abrupt/story3.html
55
The Concern

• The concern is that cool, freshwater melting off
  of the Greenland glacier will interrupt the
  Thermohaline circulation. An influx of cold
  freshwater would eliminate the halocline gradient
  and the warm Gulf Stream would cease flowing
  northward. This would act like a positive
  feedback loop in which the cooler ocean
  temperatures may spawn another ice age.
• The influx of cold water is thought to have been
  responsible for the reversal of the post-glacial
  warming trend around 14,500 years ago (aka the
  Younger Dryas Period). The blip in the warming
  trend after the Laurentide glacier retreated may
  be related to an influx of cold, freshwater in
  the Northern Atlantic.

56
Younger Dryas Example of when the Thermohaline
Circulation stopped - from the influx of glacier
meltwater
It took the Earth several thousand Years to
recover
Dryas
www.ncdc.noaa.gov/paleo/abrupt/story3.html
http//www.toyen.uio.no/botanisk/nbf/plantefoto/dr
yas _octopetala_Roger_Johansen.jpg
57
Other Concerns about a Warming Planet

• Hurricanes and Severe Weather.
• Most of the increase in hurricane size and
  periodicity (Hurricane Katrina) is related to
  decadal oscillations (AMO), and not really
  associated with global warming.
• Some researchers believe that larger and more
  hurricanes are inevitable during a warmer
  climate. Dr. Kerry Emanuel at MIT suggested
  that the intensity of Atlantic storms had on
  average doubled over 30 years (The Economist,
  Vol. 384 pg 12).
• The Tropical Storm Zeta on 12/31/05 may be
  evidence of an extended hurricane season.

58
Other Concerns

• There are far too many other topics to include.
  As a shortened summary, other factors that may be
  affected by global warming
• Changing distribution of organisms (Red fox are
  now competing with Artic fox in Alaska).
• Effects on agriculture. Russia would benefit as
  more agricultural land would be exposed the US
  might suffer with hotter/drier conditions.
  England is now growing wine again (hasnt
  occurred since Medieval periods.

59
Review to this point

• The Earths climate is getting warmer, but the
  length of this warming trend and the consequences
  that this warming trend will have are debatable.
  
• The Earth-Atmosphere system is extremely complex,
  more so then we can understand. Several
  uncertainties exist regarding how the Earth will
  react to increasing temperatures

60
Uncertainties

• The baffling complexity of the climate-and thus
  the difficulty of predicting what is going to
  happen to it-arises principally from its feedback
  loops (The Heat is On The Economist, Vol.
  384, pg. 4). The following feedbacks are
  reported from the above issue
• Albedo with an increase in ice and the
  resulting increase in the worlds albedo, more
  solar radiation should be reflected back to
  space. Thus there would be a positive feedback
  of global cooling. The converse would be that
  the reduction of glaciers would decrease the
  albedo, resulting in more solar radiation being
  absorbed.
• Ocean Absorption CO2 is more soluble in water
  in colder temperatures. As sea surface
  temperatures warm, the oceans ability to store
  CO2 would be lessened. This would be a positive
  feedback in which a warmer ocean would release
  more CO2, and in turn this would blanket the
  earth.
• Soil Respiration Warming leads to more
  microbial activity, which in turn produces more
  CO2 (via cellular respiration).
• Clouds Clouds could be a positive or negative
  feedback. By positive feedback a warmer
  climate produces more clouds that trap more solar
  radiation. Conversely the negative feedback
  could be a warmer climate produces more clouds,
  more clouds increases the atmosphere's albedo,
  which reflects more solar energy. This would
  result in a cooling trend

61
Additionally

• In addition to the complexity in understanding
  the feedback mechanisms, there are other factors
  that need to be accounted for.
• For one, temperature data over the last several
  hundred years has some inconsistencies
• Thermometers have become more accurate and more
  precise over time. Data from the early part of
  the century may not be at the same accuracy level
  as modern measurements.
• Areas have become more urban over time. The same
  thermometer may be reading warmer values in more
  recent times do to the increased urbanization
  (and resulting urban heat island). The warming
  trend , then, is more a reflection of
  urbanization than global warming.
• Weather stations have moved. See Dr. Barry
  Keims research (LSU, and Louisiana State
  Climatologist) on what affect NWS station
  relocations have had on temperature measurements.
• I bring up these points to illustrate an
  important point there are a lot of factors that
  have to be considered when examining global
  climate change, regardless of whether you are on
  one side or the other. It is not a simple, cut
  and dry issue. I am neither ruling the current
  global warming trend out or advocating it, but
  instead suggesting that more research is needed.

62
Government Responses

• What is the government doing about climate
  change?
• There are several US Government agencies
  monitoring climate change.
• There is even a US law that states the US Govt.
  must be cognizant of climate change.

63
CCSP

• The U.S. Climate Change Science Program (CCSP)
  was launched in February 2002 as a collaborative
  interagency program, under a new cabinet-level
  organization designed to improve the government
  wide management of climate science and
  climate-related technology development.
• Quote from the CCSP website.

64
U.S. Global Change Research Act of 1990Public
Law 101-606(11/16/90) 104 Stat. 3096-3104

• An Act To require the establishment of a United
  States Global Change Research Program aimed at
  understanding and responding to global change,
  including the cumulative effects of human
  activities and natural processes on the
  environment, to promote discussions toward
  international protocols in global change
  research, and for other purposes.
• Government definition of "Global change" means
  changes in the global environment (including
  alterations in climate, land productivity, oceans
  or other water resources, atmospheric chemistry,
  and ecological systems) that may alter the
  capacity of the Earth to sustain life
  (http//www.gcrio.org/gcact1990.html)

65
Other US Govt. Agencies

• In addition to the previous, other agencies are
  responsible for keeping an eye out on global
  climate change. Perhaps the most noted is NOAAs
  
• The Climate Program Office (CPO), created in
  October 2005, incorporates the Office of Global
  Programs, the Arctic Research Office, and the
  Climate Observations and Services Program and,
  coordinates climate activities across all NOAA.
  The new CPO focuses on developing a broader user
  community for climate products and services,
  provides NOAA a focal point for climate
  activities within NOAA, leads NOAA climate
  education and outreach activities, and
  coordinates international climate activities.
• NOAA's Climate goal is to "Understand and
  describe climate variability and change to
  enhance society's ability to plan and respond".

http//www.climate.noaa.gov/
66
State Law California

• On August 31, 2006 the California legislature
  passed a bill establishing the most extensive
  carbon dioxide (CO2) emission controls yet in the
  United States. The law requires a 25 percent
  reduction in state CO2 emissions by 2020, with
  the first major controls taking effect in 2012.
  The California Air Resources Board, the agency
  that enforces the states air pollution controls,
  will be the main authority in establishing
  emission targets and noncompliance penalties for
  the law, which also allows for business
  incentives to reach the goals.
  http//www.worldwatch.org/node/4499

67
Global UNs IPCC

• The Intergovernmental Panel on Climate Change
  (IPCC)
• "The role of the IPCC is to assess on a
  comprehensive, objective, open and transparent
  basis the scientific, technical and
  socio-economic information relevant to
  understanding the scientific basis of risk of
  human-induced climate change, its potential
  impacts and options for adaptation and
  mitigation. IPCC reports should be neutral with
  respect to policy, although they may need to deal
  objectively with scientific, technical and
  socio-economic factors relevant to the
  application of particular policies. Review is
  an essential part of the IPCC process. Since the
  IPCC is an intergovernmental body, review of IPCC
  documents should involve both peer review by
  experts and review by governments"

68
The Kyoto Protocol

• Meeting of 160 countries in 1997 to discuss
  measures to mitigate CO2 emissions. The
  international treaty to reduce greenhouse gasses
  took affect in 2005.
• "stabilization of greenhouse gas concentrations
  in the atmosphere at a level that would prevent
  dangerous anthropogenic interference with the
  climate system" UNFCCC-2. Quote taken from
  Wikipedia.org.
• The US and Australia did not participate and will
  not ratify the CO2 reduction legislation. Some
  of the US disagreements with the legislation are
  (1) it exempts China (the second largest producer
  of CO2) and (2) economic concerns. The absence of
  US participation (the largest CO2 producer)
  raises serious questions about the effectiveness
  of the Kyoto Protocol.

69
Concluding Remarks

• What do I hope that you got from Lecture 6
• A realization that the Earths climate changes.
  There are cooling periods and warming periods,
  and this is not uncommon during our planets
  history
• Changing climate can have really severe
  implications. This is a topic that is certainly
  worthy of attention.
• There is a great deal of uncertainty regarding
  global climate change. There are several climate
  interactions that are not fully understood.
  There are also several inconsistencies with our
  data. These factors must be taken into
  consideration.
• More research is needed. Global climate change
  is important and it could have severe
  consequences to our society. It is not to be
  taken lightly. Media hype and bad science may be
  misleading, confusing, and may be polarizing our
  society more than it needs. We need careful
  observations and unbiased interpretations.