Two global problems

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Two global problems

• Ozone layer depletion
• Global warming

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Ozone layer depletion
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The Optical Properties of Ozone
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The Optical Properties of Ozone

• In 1879, Marie Alfred Cornu observes a sharp
  cutoff (300 nm) in the ultraviolet (UV) solar
  spectrum.
• In 1881, Walter Noel Hartley measures the ozone
  absorption cross section in the laboratory and
  recognizes that this UV cutoff is produced by the
  presence of ozone in the atmosphere.
• In 1913, John William Strutt (Lord Rayleigh)
  shows that the UV absorption does not happen in
  lower atmosphere

Alfred Cornu Professor at Ecole Polytechnique
in Paris
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Ozone Observations

• Paul Götz during a Spitzbergen expedition in 1929
  (by inverting Dobson spectrophotometer
  measurements at high solar zenith angles) shows
  that the maximum ozone concentration is located
  near 25 km altitude.
• Götz and Hans Dütsch conducted systematic ozone
  observation in Arosa, Switzerland since 1926.

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Ozone and Chlorine

• At a scientific conference in Kyoto, Japan in
  1974, Richard Stolarski and Ralph Cicerone, then
  at the University of Michigan, suggested that
  chlorine could catalytically destroy ozone in the
  stratosphere.
• They note that large amounts of chlorine are
  released during volcanic eruptions

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Chlorofluorocarbons and Ozone

• In 1974, Mario Molina and Sherry Rowland at the
  University of California, Irvine, show that
  industrially manufactured chloro-fluorocarbons
  could provide the major source of stratospheric
  chlorine and therefore are a major threat to the
  ozone layer.

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The Ozone Hole A challenge for the scientific
community Observations made at the British
Antarctic station of Halley Bay (Farman and
coworkers) and the Japanese station Syowa
(Chubachi) during the 1970s and 1980s show a
dramatic decrease in the ozone column that is not
simulated by atmospheric models.
Halley Station
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The Explanations

• Early theories to explain the observed ozone hole
  refer to dynamical perturbations and solar
  variability.
• Susan Solomon and colleagues suggest that
  chlorine can be activated on the surface of polar
  stratospheric cloud (PSC) particles observed over
  Antarctica, and can destroy most of the lower
  stratospheric polar ozone in a few weeks.
• Considerable experimental work is initiated to
  study heterogeneous chemical processes

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The Antarctic Ozone Hole

• The most efficient catalytic reaction cycle
  responsible for the ozone hole is discovered by
  Mario Molina.
• Airborne field campaigns and space observations
  confirm that anthropogenic chlorine is
  responsible for the formation of the ozone hole.
• Substantial ozone destruction is also observed in
  the Arctic.

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A Success Story
The international protocol signed in Montreal,
Canada in 1987, and the subsequent amendments,
lead to a phase-out of the most ozone-damaging
chlorofluorocarbons. The ozone hole is predicted
to disappear around year 2050.
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An example to ozone destruction reactions

• CFCl3 h? ? CFCl2 Cl
• Cl O3 ? ClO O2
• ClO O ? Cl O2
• O3 O ? 2 O2
• One single free chlorine atom can catalytically
  destroy 2 ozone molecules

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Ozone destruction reactions

• If this catalytic circle is not interrupted by
  the formation of the compounds such as HCl or
  ClONO2 , one single chlorine atom continues to
  destroy ozone molecules for two years.
• Ozone destruction effect of bromine is even
  higher. Although bromine amount in the atmosphere
  is less than that of chlorine, bromine-ozone
  relation is still under investigation.

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Global warming
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Global Warming

• GW is the increase in the average temperature as
  a result of the increase in the greenhouse gases
  in the atmosphere as a result of human activities.

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IPCC report

• According to the results of the last report (4th
  report) of IPCC (Intergovernmental Panel on
  Climate Change) published in 2007
• The world climate system is under warming effect
  and this is because of human activities

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IPCC 4th Assessment Report (2007)

• More than 2500 expert views
• Contribution of 800 authors
• 450 main authors
• Contribution from more than 130 countries

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Extraordinary meteorological conditions

• In most regions, the frequency of excess rainfall
  has increased
• From 1900 to 2005, in the east of North and South
  America, in Northern Europe and in Central and
  Northern Asia amount of precipitation has
  significantly increased in the Sahel, in the
  Mediterranean, in Southern Africa and in some
  parts of Southern Asia amount of precipitation
  has significantly decreased.
• Globally, total area affected by drought seems to
  have increased since 1970.
• Global average sea level increase rate has
  increased from 1.8 mm/year in 1961 to 3.1 mm/year
  in 1993.
• Projections of sea level increase by the end of
  the 21st century is in the range of 18-59 cm

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• Difference from 1961-1990 average
• Average global temperature
• Average sea level
• Snow cover at the North Pole

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• 2020de Afrika
• 75-250 milyon insanin yasadigi su stresi artmis
  olacak
• Bazi ülkelerde, yagmura dayali tarim
  ürünlerindeki verim 50 azalacak
• 2050de Asya
• Projeksiyonlara göre tatlisu kaynaklari azalacak
• Kiyi bölgeleri, özellikle nüfus yogunlugunun
  yüksek oldugu büyük delta bölgelerinde büyük
  deniz taskini riski altinda olacak

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Global Warming Potential (GWP)

• GWP is the indicator of the contribution of a
  greenhouse gas to global warming.
• It is a relative scale. It is the comparison of
  the potential of the gas of concern to that of
  the potential of CO2 with the same mass.
• GWP of CO2 is 1.
• It is estimated for a certain time interval

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GWP values according to the 4th IPCC report (the
values in parentheses are from the 3rd assessment
report)
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Most Important Greenhouse Gases

• CO2
• CH4
• N2O
• HFCs
• PFCs
• SF6
• CFCs

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Water

• Although H2O is one of the strongest greenhouse
  gases, GWP value is generally not estimated for
  water.
• THe reason of this is that the atmospheric levels
  of water vapor depends on meteorological
  conditions, especially temperature.
• Although there is water vapor emission from
  anthropogenic sources such as combustion, this
  factor is not significant compared to the effect
  of the meteorological conditions.
• But Since the average water vapor amount of the
  atmosphere is predicted to increase as a result
  of global warming, the effect of water vapor is
  still of important concern in global warming
  studies

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Sources of Greenhouse Gases

• CO2 Fossil fuel combustion, fermentation
  byproducts, thermal desorption of CaCO3, food
  industry, chemical industry, etc
• PFC medicine, eye surgery, ultrasound
  applications, refrigerants, fire extinguishers,
  etc
• CH4 Natural sources (wetlands, rice production,
  oceans, etc) and anthropogenic sources (energy,
  waste dumps, biomass burning, etc)
• N2O Medicine, anesthetics, sprays, food
  additive, rocket motors, race cars, soil and
  ocean bacteria, biomass burning, etc
• SF6 Electric industry, magnesium industry,
  medicine, filling material (car tires, windows),
  etc
• HFC Polymerization, refrigerants, fire
  extinguishers

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Radiative Forcing

• In climate science, radiative forcing is
  (loosely) defined as the change in net irradiance
  at the tropopause. "Net irradiance" is the
  difference between the incoming radiation energy
  and the outgoing radiation energy in a given
  climate system
• The radiative forcing of the surface-troposphere
  system due to the perturbation in or the
  introduction of an agent (say, a change in
  greenhouse gas concentrations) is the change in
  net (down minus up) irradiance (solar plus
  long-wave in Wm-2) at the tropopause AFTER
  allowing for stratospheric temperatures to
  readjust to radiative equilibrium, but with
  surface and tropospheric temperatures and state
  held fixed at the unperturbed values

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Global warming or cooling?

• According to one opinion, since particulate
  matter emission increases because of pollution
  and since particulate matter mostly has a cooling
  effect( because of the scattering of sunlight),
  the net radiative forcing is not positive (i.e.
  there is no net warming)

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IPCC (2007)