Climate Change and Climate Modeling

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Climate Change and Climate Modeling Kristina
Fitzhugh November 17, 2009
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Earthrise
The picture became known as Earthrise and the
image of the world from the perspective of a
desolate lunar surface became an iconic reminder
of our need to protect the Earths fragile
resources. Earthrise and images like it are
widely credited with inspiring the environmental
movement and indirectly the start of the
Environmental Protection Agency in 1970. (5)
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What is Climate Change?

• A long-term change in the Earths climate, or of
  a region on Earth
• Can be the change in average weather or change in
  weather distributions
• (ex fewer or greater extreme weather events)
• Can occur locally, regionally, or globally
  (1,2,4)

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Misconception 1

• Temperatures in some areas arent increasing, so
  global warming is a myth.
• It is certainly true that the temperature is not
  rising at every point on the planet...global
  warming refers to the rise in average
  temperature...the impacts of climate change will
  not be the same everywhere

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Climate Change vs. Global Warming

• Terms sometimes used interchangeably
• Global warming refers to the average surface
  temperature increase caused by rising levels of
  greenhouse gases (ghgs)
• Originally introduced in a 1975 Science article
  by geochemist Wallace Broecker of Columbia
  University
• Previously referred to as inadvertent climate
  modification (4)

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Climate Change vs. Global Warming

• Scientist knew human activity would affect the
  climate, but they didnt know how
• In 1979 the National Academy of Science conducted
  a study on the effects of carbon dioxide on
  climate
• Adopted Broeckers term when referring to rising
  surface temperatures
• Used climate change when referring to other
  changes to the climate (4)

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Misconception 2

• Scientists disagree about whether humans are
  causing the Earths climate to change
• Scientists overwhelmingly agree that the Earth
  is getting warmer, that this trend is caused by
  people, and that if we continue to pump
  greenhouse gases into the atmosphere, the warming
  will be increasingly harmful

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Causes of Climate Change

• Plate tectonics
• Ocean currents
• Volcanoes
• Earths orbit and tilt
• Greenhouse gases

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Plate Tectonics Ocean Currents

• Earths lithosphere is broken into tectonic
  plates
• Plates sit on the asthenosphere
• Plates move in relation with one another at plate
  boundaries
• Moved by convection currents beneath the plates
• Position of continents affect ocean currents
  (4)

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Plate Tectonics Ocean Currents

• The ocean is important in controlling heat and
  moisture transfer
• Location of land masses affects the distribution
  of temperature
• Affects climate around the world (4)

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Volcanoes

• Emit aerosols and carbon dioxide into the
  atmosphere
• Aerosols block sunlight and causes short term
  cooling, though no long term affects
• CO2 causes warming, but relatively small amount
  released compared to humans (6)

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Earths Orbit Tilt

• Majority of Earths land mass is above the
  equator
• Spring/Summer Northern Hemisphere is pointed
  toward the Sun
• Fall/Winter Northern Hemisphere is pointed away
  from the Sun (7)

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Greenhouse Effect

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Greenhouse Gases

• Water vapor the most abundant ghg, increases
  clouds and precipitation so important feedback to
  the climate
• Methane produced naturally and through human
  processes, much less abundant than other ghgs
• decomposition of waste, rice cultivation,
  livestock
• Nitrous oxide produced naturally and through
  human processes
• microbials in soil, agriculture soil management,
  sewage treatment
  
  (8)

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Greenhouse Gases

• Chlorofluorocarbons completely of industrial
  origin, severe depletion of ozone layer
• 1987 Montreal Protocol complete elimination of
  CFCs by 2000, gone from developing countries by
  2010
• Carbon dioxide produced naturally and through
  human processes, most important ghg
  
  
  (8)

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Carbon Dioxide Emissions
(9)
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Misconception 3

• Climate naturally varies over time, so any change
  were seeing now is just a part of a natural
  cycle
• Climate does naturally change....but these
  changes all took place with natural variations in
  carbon dioxide levels that were smaller than the
  one we are now causing...carbon dioxide levels
  are higher now than they have been at any time in
  the last 650,000 years, which means we are
  outside the realm of natural climate variation.

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Misconception 4

• Antarcticas ice sheets are growing, so it must
  not be true that global warming is causing
  glaciers and sea ice to melt.
• Some ice on Antarctica may be growing...study
  shows that overall the ice is shrinking in
  Antarctica...Globally more than 85 of glaciers
  are shrinking.

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Hurricane Katrina

• Less than a month before Hurricane Katrina hit
  New Orleans and the South with its huge forces,
  MIT had released a study that said...
• Major storms spinning in both the Atlantic and
  the Pacific since the 1970s have increased in
  duration and intensity by about 50 percent
  (7)

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Climate Models

• Study dynamic climate system
• Predict relation of ghg emissions and future
  climate
• Predict regional environments, such as future
  stream flow or vegetation changes
• 2007 International Panel on Climate Change Report
  models show predicted ranges for average
  worldwide temperature increase of
• Low range (1.1 2.9) 1.8 C
• High range (2.4 6.4) 4.0 C (11)

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Simple Climate Model

• Want to find Earths temperature from an energy
  model in equilibrium
• solar radiation (S) 1370/4
• of albedo (a) 0.3
• Stefan Boltzmann constant (q) 5.67 x 10-8
• Temperature (T)
  
• 
  
  (13)

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Stefan Boltzmann Constant

• All bodies radiate energy as electromagnetic
  radiation
• SB Law is the total energy, I, emitted by a black
  body at any temperature, T, by
• I(T) q(T4)
• I energy per unit area emitted per second
• T absolute temperature (K)
• q Stefan Boltzmann constant
• 
  
  (13)

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Simple Climate Model

• Looking for the Earths temperature
• T (S/q)(1/4)
• Plugging in values from previous slides we get...
• T (1370/4)/(5.67 x 10-8)(1/4) 279 K 6 C
• Too cold!
  (13)

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Slightly More Complicated Model

• Looking for the Earths temperature
• T (S(1-a)(1Tvis))/(q(1Tir)(1/4)
• S, a, and q are previously defined
• Tvisproportion of incoming energy absorbed by
  the atmosphere
• Tirproportion of infrared energy not absorbed by
  the atmosphere
• Plugging in we get...
• T 288.5 K 15.5 C
• Average surface temperature of Earth currently 16
  C (12,13)

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Climate Models

• More accurate model
• The model gets very complicated very fast
• Add seasonal cycle
• Cover whole Earth (sphere)
• Plants, clouds, etc.
• Derived from fundamental physical laws, empirical
  data, observations
• Ex Newtons Law of Motion, Conservation of
  Energy, etc.
• Altered to fit large-scale climate system by
  adding details about Earths geography
• Ex topography and vegetation
  (12,14,15)

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Climate Models
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Climate Models

• Earth Simulator
• Was the fastest supercomputer in the world from
  2002-2004
• Used to run global climate models to evaluate
  the effects of global warming and problems in
  solid earth geophysics
• 35.86 trillion floating point calculations per
  second (2)

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Earth Simulator
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Do They Really Work?

• IPCC says they have considerable confidence
• Have ability to reproduce features of past and
  current climate
• Cannot reproduce the weather of a specific day,
  but can calculate the average weather conditions
• Confidence higher for predictions of some weather
  circumstances than others
• Higher for temperature than precipitation
  (14)

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Implications of Climate Change

• Decrease in biodiversity
• Sea level rise
• Higher population concentration
• Spread of disease
• And the list goes on...
• The Himalayas contain 100 times as much ice as
  the Alps and provide more than half of the
  drinking water for 40 of the worlds
  population...that 40 of the worlds people may
  well face a very serious drinking water shortage
  (7)

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Misconception 5

• There is nothing we can do about climate change.
  Its already too late.
• There are lots of things we can do but we need
  to start now...We need to reduce our use of
  fossil fuels, through a combination of government
  initiatives, industry innovation, and individual
  action.

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What Can We Do?

• U.S. Mayors Climate Protection Agreement
• Over 500 cities
• Save energy at home
• Lighting, appliances, heating and cooling
• Reduce miles driven
• Public transportation, walk, bike
• Consume less, conserve more
• http//www.youtube.com/watch?vs-_LBXWMCAM

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Sources

• http//www.ecy.wa.gov/climatechange/whatis.htmQ1
• http//www.wikipedia.org
• http//www.epa.gov/climatechange/science/recentac.
  html
• http//www.nasa.gov/topics/earth/features/climate_
  by_any_other_name.html
• http//blog.epa.gov/blog/2009/07/01/science-wednes
  day-earthrise/
• http//www.epa.gov/climatechange/science/pastcc.ht
  ml
• An Inconvenient Truth by Al Gore
• http//climate.nasa.gov/causes/
• http//www.epa.gov/climatechange/emissions/co2_hum
  an.html
• http//www.atmos.washington.edu/aaron/How20do20
  Climate20Models20Work.ppt273,18,Greenhouse
  gases
• http//www.ipcc.ch/pdf/assessment-report/ar4/wg1/a
  r4-wg1-spm.pdf
• http//www.atmos.washington.edu/aaron/How20do20
  Climate20Models20Work.ppt273,18,Greenhouse
  gases
• http//www.scienceinschool.org/2008/issue9/climate
  
• http//www.ipcc.ch/pdf/assessment-report/ar4/wg1/a
  r4-wg1-chapter8.pdf
• http//www.southwestclimatechange.org/climate/mode
  ling/how-models-work