Earth Systems Science Chapter 1

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Earth Systems ScienceChapter 1

• I. CHANGES
• it is the nature of dynamic systems to change,
  often even in the absence of external forcings.
  Some important environmental problems today
  require discriminating between natural and
  anthropogenic changes.
• Human impact on local environments have been
  known for years e.g. deforestation in New
  England and Europe
• Today, regional impacts (acid rain, air
  pollution) and global impacts (global warming,
  stratospheric ozone, deforestation) are also
  realized to be important.

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• II. 3 MAJOR THEMES OF THE TEXT
• 1. Global environmental issues (global warming,
  stratospheric ozone, deforestation)
• 2. Paleo-environmental changes
• 3. Systems
• Our goal in this class is to cover 1 and 2 as
  we go, but to really focus on 3.
• The Earth System atmosphere, hydrosphere,
  lithosphere, biosphere. In this course we focus
  on the first three, the continuation of this
  course will focus more on the biosphere.

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• III. GLOBAL CHANGE ON SHORT TIME SCALES
• 1. Global Warming
• 2. Stratospheric Ozone Depletion
• 3. Deforestation and Loss of Biodiversity
• How are these problems related?
• How are they examples of dynamic systems /
  dynamic equilibrium

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• 1. GLOBAL WARMING
• define global warming, greenhouse effect
• EVIDENCE OF GREENHOUSE GAS CHANGES
• CO2 fluctuations Keeling curve, and ice core
  data
• Other greenhouse gases methane (CH4), nitrous
  oxide (N20), and CFCs.
• EVIDENCE OF TEMPERATURE CHANGES
• Surface temperature observations

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The Keeling Curve
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Ice Core Data and The Keeling Curve
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Warming over the past 50 years

• Simulations with natural and human factors match
  observations best
• Correspondences increase with time
• Probability is low that natural-only earth
  would have such correspondences

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The Land Surface We see
that the physical processes that occur at the
surface of the Earth are, have to be, in the
middle of the controversy over the impact of
human activities on climate, since there is where
we live and it is over land that most of the
anthropogenic climate forcing is found.
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Deforestation in the U.S. Loss of Virgin Forests
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Deforestation and urbanization are human
activities that impact the land surface
heterogeneities, as the example of fish-bone
pattern of deforestation typical of small farm
holdings in Rondônia, Brazil, illustrates.
Deforestation of Rondônia within 13 years
(Landsat image) This introduces small-scale
heterogeneities at the surface.
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US-Mexico border in California, area of 24
by 30 km.
El Centro, CA
Mexicali-Calexico
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Surface Temperature Observations
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http//www.cru.uea.ac.uk/cru/info/warming/
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• 2. STRATOSPHERIC OZONE DEPLETION
• stratospheric vs tropospheric ozone
• The ozone hole How was it discovered, how was it
  solved (not in text)
• Ozone depletions in other regions

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The Antarctic Ozone Hole
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The Antarctic Ozone Hole
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• 3. DEFORESTATION AND LOSS OF BIODIVERSITY
• e.g. Europe, New England, and now tropical
  forests
• Always changes the landscape, often reduces the
  complexity (e.g. forest to crops) in terms of
  flora and fauna
• Global tropical forest coverage less than half
  the area estimated for prehistoric times.

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• Global Warming
• Stratospheric Ozone Depletion
• Deforestation and Loss of Biodiversity
• HOW ARE THESE DIFFERENT PROBLEMS RELATED?
• HOW ARE EACH OF THESE AN EXAMPLE OF DYNAMIC
  EQUILIBRIUM ?

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• IV. GLOBAL CHANGE ON LONG TIME SCALES
• Long thousands of years or more
• Geologic Time Scale eon, era, period, epoch
• Three examples of long term changes
• 1. GLACIAL CYCLES The Vostok Ice core data
• 2. MASS EXTINCTIONS Iridium at the K-T boundary
• 3. CHANGES IN SOLAR LUMINOSITY the faint
  young sun paradox

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• GEOLOGIC TIME SCALE
• Eon 108-1010 yrs
• Era 107-108 yrs
• Period 106-107 yrs
• Epoch 104-106 yrs

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GEOLOGIC TIME SCALE
Glacial Cycles
K-T Boundary
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1. GLACIAL CYCLES THE VOSTOK ICE-CORE DATA
C02, CH4, and temperature time series for the
last 400,000 years How are they derived
isotope analysis (O and H) These co-varying
changes are interpreted as evidence of
system-like behavior
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• 2. MASS EXTINCTIONS IRIDIUM AT THE K-T BOUNDARY
• Extinction of dinosaurs, many other marine and
  terrestrial species (both animal and plant)
• Iridium deposited at a very slow, but known,
  rate from extraterrestrial sources. The iridium
  concentrations in the layer at the K-T boundary
  were so high that it could not have been
  deposited by normal deposition. So, it must have
  been a very massive, sudden extraterrestrial
  source.
• Example of a shock to the earth system. The
  climate, biosphere, recovered, but at different
  rates. Biosphere recovery was very different
  from prior biosphere.
• Relevance to anthropogenic changes in
  biodiversity today

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IRIDIUM AT THE K-T BOUNDARY
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• 3. CHANGES IN SOLAR LUMINOSITY
• Solar physicists tell us that the amount of
  energy emitted by the sun was 30 less 4.6
  billion years ago when the sun formed
• The faint young sun paradox why wasnt the
  earth frozen over when the solar luminosity was
  so low?

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• 3. CHANGES IN SOLAR LUMINOSITY (contd)
• The Gaia Hypothesis Lovelock and Margulis.
  Believe that the biosphere, responding to
  climatic changes, have affected the earth system
  in such a way as to help maintain a relatively
  stable climate. Not a conscience action not
  resilient to all possible changes
• Also possible that abiotic factors in the earth
  system played a role, not necessarily the
  biosphere.