How to study

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How to study

• Course and lecture goals!

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Efficiency

• A 100g bar of chocolate contains about 500 kcal
  2100 kJ of chemical energy. If ones body can
  convert it to 315kJ of mechanical energy we say
  that the efficiency is 315/2100 15
• Similarly if a car engine converts 20 of
  chemical energy contained in gas to mechanical
  energy we say that its efficiency is 20.

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• Combining these two equations
• s TEarth4 e s TA4 s Ts4
• TA4 Ts4 /2
• we have s TEarth4 e s Ts4/2 s Ts4
• Ts4 2TEarth4/(2-e)
• Analyzing the infrared absorption
• curve gives average e 0.9
• so we obtain
• Ts 23 ºC

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Earth Energy Balance

• The more complex models involving multilayer
  atmosphere partly transparent in infrared are
  coming up with proper average temperature of the
  surface of the Earth, which is about 15 ºC
• The process we followed is the process of
  consecutive approximation in modeling. Very often
  we start with a very simple model and progress to
  more complicated once getting (hopefully) closer
  and closer to reality.

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Different layers of the atmosphere
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Earth Energy Balance
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Feedback Negative feedback and its role in
keeping the equilibrium

• Examples
• thermostat,
• steering wheel corrections on a straight road,
• water level in the toilet reservoir.
• Bull and Bear markets negative feedback
• Bull market a prolonged period in which
  investment prices (shares) rise
• bear market a prolonged period in which
  investment prices fall

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Feedback Positive feedback and its role in
leading to catastrophe

• Examples
• reverse connected steering wheel,
• water level in the toilet reservoir with badly
  connected valve.
• Bull and Bear markets positive feedback

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Greenhouse Effect

• http//phet.colorado.edu/web-pages/simulations-bas
  e.html

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History of Earth Climate
http//vathena.arc.nasa.gov/curric/land/global/cli
mchng.html
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History of Earth Climate
http//vathena.arc.nasa.gov/curric/land/global/cli
mchng.html
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History of Earth Climate How do we know it?

• The geological record of carved mountain valleys,
  scratched bedrock, and glacial debris and
  moraines gives evidence of the past several
  million years.
• Recently, cores have been removed from the ice at
  Vostok Station in Antarctica. The longest cores
  are about 2000 meters, sampling layers of ice
  deposited as early as 160,000 years ago. The ice
  trapped bubbles of air when it froze. The ratio
  of oxygen isotopes in this air indicates the
  average air temperature at the time the bubble
  was trapped in ice. The bubbles also trap
  atmospheric greenhouse gases that can be
  measured.
• Fossil plants and the distribution of pollen show
  that vegetation has changed, consistent with
  changing climate. Pollen from plants, buried in
  shallow deposits of earth, indicate the
  distribution of vegetation since the last
  glaciation, about 20,000 years ago. Ancient
  Plant Distribution describes how vegetation has
  changed as the ice retreated, and offers a
  student activity.
• Tree rings provide a record of the weather back
  3,000 years in some cases, and hundreds of years
  in many areas. See Tree Rings, a Study of Climate
  Change.
• The historical record speaks to us for some 2,000
  years and there have been real quantitative
  measurements since about 1850.

http//vathena.arc.nasa.gov/curric/land/global/cli
mchng.html
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Feedback in the Earth's climate system

• Albedo effects positive feedback
• Snowball Earth
• Black Earth
• Final state how the feedback mechanism ends?
• Ways out
• Volcano eruptions,
• Large asteroid impact

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What may influence climate

• Solar activity
• Earth orbit
• Earth axis tilt
• Volcanoes
• nuclear winter or ash winter
• deposits
• Asteroid impacts

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History of the climate

• Climate and human history
• Journey webpage
• Why worry now?

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Solar movie
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(No Transcript)
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Greenhouse Effect

• http//phet.colorado.edu/web-pages/simulations-bas
  e.html

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Absorption in the infrared region.
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Positive Feedback example in climate

• CO2 is a greenhouse gas.
• It dissolves in water.
• As the temperature increases the solubility of
  CO2 decreases.
• Increase of amount of CO2 leads to increase of
  temperature, which leads to release of CO2 from
  the oceans.
• Positive feedback.
• Notice that a small increase of CO2 in the
  atmosphere can start this process

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Negative Feedback example in climate

• Increase in temperature increases evaporation
  rate of water from the Oceans and therefore
  increases the amount of cloud cover. The
  increased cloud thickness or extent increases
  Earths Albedo and therefore could reduce
  incoming solar radiation and limit warming.
• On the other hand it is not obvious that if
  additional cloud cover happens at what latitudes
  and at what times might it occur. Also it is not
  obvious what types of clouds might be generated.
  Thick low clouds would have a stronger ability to
  block sunlight than extensive high (cirrus) type
  clouds.

http//www.globalchange.umich.edu/globalchange1/cu
rrent/lectures/samson/feedback_mechanisms/
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The same process can create both positive and
negative feedback

• Increase of the amount of water vapor in the
  atmosphere increases the cloud cover and so
  decreases the temperature.
• But the water is a greenhouse gas so the increase
  in temperature would permit more water vapor to
  be stored in the atmosphere. The amount of water
  vapor the atmosphere can hold increases
  exponentially with temperature so increases in
  temperature can yield increases in atmospheric
  water vapor. The increased water vapor, as a
  greenhouse gas, enhances the greenhouse effect
  and could lead to further warming as long as this
  positive feedback isn't modified by an increase
  in cloud cover that could lead to a negative
  feedback.

http//www.globalchange.umich.edu/globalchange1/cu
rrent/lectures/samson/feedback_mechanisms/
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Compelling evidence for global warming

• Temperature curves
• Glaciers and arctic ice disappearing
• Possible explanations
• Continuation of warming after little ice age in
  middle ages
• Solar activity
• Human influence
• Modeling of the climate.
• Difficulties
• Model testing
• Fits, available amount of data (remember fitting
  to 4 points and than to more during the lab?)

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http//vathena.arc.nasa.gov/curric/land/global/cli
mchng.html
The last century curve
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Temperature variation last 150 years
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(No Transcript)
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If humans, than what we did?

• Greenhouse gases
• Ozone layer
• What is the influence of ozone layer on climate
• Ozone layer destructive gases
• Deforestation - what is the feedback effect here?

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The net effect of Ozone depletion on Earth
temperature is cooling. It is a greenhouse gas in
the region different from CO2 and H2O
http//www.ipcc.ch/press/SPM.pdf
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http//www.globalchange.umich.edu/globalchange1/cu
rrent/lectures/samson/feedback_mechanisms/
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Sophisticated climate models
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We will discuss the effects of energy production
later
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August 4, 2007Walking to the shops damages
planet more than going by car

• Food production as a source of greenhouse gases.
• Assumptions made by the author of this statement
• The caloric intake needed to walk taken solely
  from beef.
• No accounting of making and recycling of the car

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Other controversial statements about the climate
changes

• Traditional nappies are as bad as disposables, a
  study by the Environment Agency found. While
  throwaway nappies make up 0.1 per cent of
  landfill waste, the cloth variety are a waste of
  energy, clean water and detergent
• Paper bags cause more global warming than
  plastic. They need much more space to store so
  require extra energy to transport them from
  manufacturers to shops
• Diesel trains in rural Britain are more polluting
  than 4x4 vehicles. Douglas Alexander, when
  Transport Secretary, said If ten or fewer
  people travel in a Sprinter train, it would be
  less environmentally damaging to give them each a
  Land Rover Freelander and tell them to drive
• Burning wood for fuel is better for the
  environment than recycling it, the Department for
  Environment, Food and Rural Affairs discovered
• Organic dairy cows are worse for the climate.
  They produce less milk so their methane emissions
  per liter are higher
• Someone who installs a green light bulb undoes
  a years worth of energy-saving by buying two
  bags of imported vegetables, as so much carbon is
  wasted flying the food to Britain
• Trees, regarded as shields against global warming
  because they absorb carbon, were found by German
  scientists to be major producers of methane, a
  much more harmful greenhouse gas
• Sources Defra How to Live a Low-Carbon Life, by
  Chris Goodall Absorbent Hygiene Products
  Manufacturers Association The Times BBC

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• Prof. John Mitchell OBE FRS, Chief Scientist at
  the Met Office explores some of the common myths
  about climate change.The Met Office recognises
  that climate change is a complex subject. There
  are genuine areas of uncertainty and scientific
  controversy. There are also a number of
  misunderstandings and myths which are recycled,
  often by non-climate scientists, and portrayed as
  scientific fact.Recent coverage has questioned
  the influence of humans on the climate. While the
  arguments used might have been regarded as
  genuine areas of sceptical enquiry 20 years ago,
  further observed warming and advances in climate
  science render these out of touch. Myth 1 - Ice
  core records show that changes in temperature
  drive changes in carbon dioxide, and it is not
  carbon dioxide that is driving the current
  warming
• Levels of atmospheric CO2 are higher than at any
  time in the last 430,000 years Click on the image
  for a larger view Only the first part of this
  statement is true. Over the several hundred
  thousand years covered by the ice core record,
  the temperature changes were primarily driven by
  changes in the Earths orbit around the sun. Over
  this period, changes in temperature did drive
  changes in carbon dioxide (CO2). Concentrations
  of CO2 are now much higher and increasing much
  faster than at any time in at least the last
  600,000 years. This should be a warning that what
  is happening now is very different to what
  happened in the past. In fact, over the last 100
  years CO2 concentrations have increased by 30
  due mainly to human-induced emissions from fossil
  fuels. Because CO2 is a greenhouse gas, the
  increased concentrations have contributed to the
  recent warming and probably most of the warming
  over the last 50 years.The bottom line is that
  temperature and CO2 concentrations are linked. In
  recent ice ages, natural changes in the climate
  (due to orbit changes for example) led to cooling
  of the climate system. This caused a fall in CO2
  concentrations which weakened the greenhouse
  effect and amplified the cooling. Now the link
  between temperature and CO2 is working in the
  opposite direction. Human-induced increases in
  CO2 is enhancing the greenhouse effect and
  amplifying the recent warming. Myth 2 - Solar
  activity is the main driver of climate change
• Temperature change, 1850-2000 Click on the image
  for a larger viewThere are many factors which may
  contribute to climate change. For example, over
  the last million years most of the long-term
  changes in climate were probably due to small but
  well understood changes in the Earths orbit
  around the Sun. Over much of the last 1,000 years
  most of the variability can probably be explained
  by cooling due to major volcanic eruptions and
  changes in solar heating.However, the situation
  in the 20th century is more complicated. There is
  some evidence that increases in solar heating may
  have led to some warming early in the 20th
  century, but direct satellite measurements show
  no appreciable change in solar heating over the
  last three decades. Three major volcanic
  eruptions in 1963, 1982 and 1991 have led to
  short periods of cooling. Throughout the century
  CO2 increased steadily and has been shown to be
  responsible for most of the warming in the second
  half of the century. The final piece of the
  jigsaw is that as well as producing CO2, burning
  fossil fuels also produces small particles called
  aerosols which cool the climate by reflecting
  sunlight back into space. These have increased
  steadily in concentration over the 20th century,
  which has probably offset some of the warming we
  have seen. Only when all of these factors are
  included do we get a satisfactory explanation of
  the magnitude and patterns of climate change over
  the last century.The bottom line is that changes
  in solar activity do affect global temperatures.
  However, what research also shows is that
  increased greenhouse gas concentrations have a
  much greater effect than changes in the Suns
  energy over the last 50 years. Myth 3 - There is
  less warming in the upper atmosphere than at the
  surface which disproves human-induced warming
• We expect greater warming in the upper atmosphere
  than at the surface in the tropics, but the
  reverse is true at high latitudes. This
  expectation holds whether the cause of warming is
  due to greenhouse gases or changes in the Suns
  output. Until recently, measurements of the
  temperature changes in the tropics in recent
  decades did not appear to show greater warming
  aloft than at the surface. It has now been shown
  that allowing for uncertainties in the
  observations, the theoretical and modelling
  results can be reconciled with the
  observations.The bottom line is that the range of
  available information is now consistent with
  increased warming through the troposphere (the
  lowest region of the atmosphere). Myth 4 - The
  intensity of cosmic rays changes climate
• Solar activity, 1850-2000 Click on the image for
  a larger viewA recent experiment has apparently
  shown that gamma radiation can form ions
  (electrically charged particles) in the
  atmosphere. Under certain circumstances, these
  can subsequently form ultra-fine particles (or
  aerosols), which could conceivably act as cloud
  condensation nuclei (CCN) and therefore form
  clouds. However, the mechanism by which cosmic
  rays might affect climate is as yet purely
  speculative and unquantified. While it has long
  been known that radiation could form ions and, in
  theory, ultimately lead to cloud formation, the
  importance of this process compared to all the
  other major sources of particles and CCN has not
  been proven. Indeed, there is no evidence that
  the flux of cosmic rays has decreased over the
  last 30 years.The bottom line is, even if cosmic
  rays have a detectable effect on climate (and
  this remains unproven), measured solar activity
  over the last few decades has not significantly
  changed and cannot explain the continued warming
  trend. In contrast, increases in CO2 are well
  measured and its warming effect is well
  quantified. It offers the most plausible
  explanation of most of the recent warming and
  future increases. Myth 5 - Climate models are too
  complex and uncertain to provide useful
  projections of climate change
• There have been major advances in the development
  and use of models over the last 20 years. The
  models are based mainly on the laws of physics.
  There are also empirical techniques which use,
  for example, studies of detailed processes
  involved in cloud formation. The most advanced
  computer models also include detailed coupling of
  the circulations of atmosphere and oceans, along
  with detailed descriptions of the feedbacks
  between all components of the climate system
  including the cryosphere and biosphere. Climate
  models have been used to reproduce the main
  features of the current climate, the temperature
  changes over the last hundred years and the main
  features of the Holocene (6,000 years ago) and
  Last Glacial Maximum (21,000) years ago.The
  bottom line is that current models enable us to
  attribute the causes of past climate change and
  predict the main features of the future climate
  with a high degree of confidence. We now need to
  provide more regional detail and more complete
  analysis of extreme events. Met Office work on
  climate change
• The Met Office Hadley Centre was opened in the
  early 1990s and is a world-leading climate
  centre. It has over 150 world-renowned climate
  experts who draw from the expertise of the
  supercomputer modellers at the Met Office.It is
  the UKs official centre for climate change
  research partly funded by Defra (the Department
  for Environment Food and Rural Affairs) and MOD
  which provides in-depth information and advice to
  the Government on climate change issues.It
  undertakes studies of the global climate using
  similar, though more extensive, models of the
  atmosphere used for the prediction of weather
  conditions.It informs the work of the
  Intergovernmental Panel on Climate Change (IPCC)
  and was the leading UK contributor to the Fourth
  Assessment Review published in February 2007. It
  assembled much of the scientific basis of the
  Stern Review on the Economics of Climate Change
  (pub. October 2006). Its research also informs
  the UK Climate Impacts Programme on how climate
  change will impact at regional and national
  levels in the UK.It advises businesses and
  governments on the science of climate change and
  strategies for mitigation and adaptation.Media
  centre
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