MET 112 Global Climate Change Lecture 14

1
MET 112 Global Climate Change - Lecture 14

• Daisyworld
• Eugene Cordero
• San Jose State University

• Outline
• Introduction
• Analysis
• Conclusions

2

• A long time ago, in a galaxy far, far away...
• existed a land called Daisyworld.
• Planet of same size, rotation, distance from the
  Sun as Earth
• Sun of the same mass and luminosity as our sun,
• Daisyworld is cloudless, no greenhouse gases,
  more land than ocean area.
• Fertile, well watered soil, plants will grow
  anywhere if the temperature is right
• Environment characterized by a single variable
  temperature
• 2 daisy species, one with light colored flowers,
  one with dark colored flowers.
• ?light 0.7, ?dark 0.2, ?bareground 0.4.
• All daisies are capable of reproducing.
• Below 5oC, no daisies grow,
• Over 40oC, all daisies die,
• 20oC is optimal for growth of all daisies.

3

• Imagine that the sun of Daisyworld varies from
  60 to 150 of present luminosity over geologic
  time scales.
• What would happen to daisyworld during this
  change in solar luminosity?

4
http//cs.clark.edu/mac/physlets/DaisyWorld/Daisy
.htm?l10.75aw0.2ab0.2
5

• Activity 7
• Answer the following questions in groups of 2
  (new partner!)
• Graph the temperature versus solar luminosity for
  daisyworld.
• Explain how both temperature and albedo change on
  Daisyworld as the solar luminosity increases from
  0.5 to 1.5 (0.5, 0.7, 0.9, 1.1, 1,3, 1.5)
• 3. Describe the feedback processes that occur
  during this experiment. Hint there may be more
  than one!
• 4. What conclusions might you come up with in
  regards to how the daisies affected climate?
• 5. How could the conclusions of daisyworld be
  applied to the climate of earth? (not in terms
  of just daisies but more broadly in terms of
  life)

6
A new theory of how the world works

• In 1965, James Lovelock, a atmospheric chemist,
  was thinking about why life evolved on earth and
  not on Mars or Venus
• Why has temp of earths surface remained in
  narrow range for last 3.6 billion years when heat
  of sun has increased by 25? Also, why has
  oxygen remained near 21?

7
Answers

• Difficult to understood without considering role
  of life
• We understand that abiotic (non-living) factors
  (physical, geological and chemical) determine
  biological outcomes
• New idea is that Biotic (living) factors feedback
  to control abiotic factors.
• Example

8
Answers

• Difficult to understood without considering role
  of life
• We understand that abiotic (non-living) factors
  (physical, geological and chemical) determine
  biological outcomes
• New idea is that Biotic (living) factors feedback
  to control abiotic factors.
• Example

Increased Planetary Temperature
Increased Planetary Albedo
Sparser Vegetation, More Desertification
Reduced Temperature
9
Gaia Hypothesis(proposed in late 70s)
Life collectively has a significant effect on
earths environment

Goes beyond simple interactions amongst biotic
and abiotic factors
Evolution of life and Evolution of its
environment are intertwined

Biosphere can be modeled as a single giant
organism
10
Gaia Hypothesis(proposed in late 70s)
Life collectively has a significant effect on
earths environment
Atmosphere-Biosphere interactions are Dominated
by negative feedback
Goes beyond simple interactions amongst biotic
and abiotic factors
Evolution of life and Evolution of its
environment are intertwined
Life optimizes the abiotic environment to best
meet biospheres needs
Biosphere can be modeled as a single giant
organism
11
Gaia Hypothesis

• Proposed by James Lovelock in mid 1960s
• States that the earth is alive as a complex
  living being.
• Life and environment evolve as a single system.
• Quite controversial theory

12
A scientific twist of an old idea?

• The concept of Mother Earth has been part of
  many cultures.
• The ancient Greeks called their Earth goddess Ge
  or Gaia
• Lovelock defines Gaia
• "as a complex entity involving the Earth's
  biosphere, atmosphere, oceans, and soil the
  totality constituting a feedback or cybernetic
  system which seeks an optimal physical and
  chemical environment for life on this planet.
• Through Gaia, the Earth sustains a kind of
  homeostasis

13
A scientific twist of an old idea?

• The concept of Mother Earth has been part of
  many cultures.
• The ancient Greeks called their Earth goddess Ge
  or Gaia
• Lovelock defines Gaia
• "as a complex entity involving the Earth's
  biosphere, atmosphere, oceans, and soil the
  totality constituting a feedback or cybernetic
  system which seeks an optimal physical and
  chemical environment for life on this planet.
• Through Gaia, the Earth sustains a kind of
  homeostasis (metabolic equilibrium maintained by
  various mechanisms),

14
Gaia Theory

• According to Dr. Lovelock
• Gaia theory predicts that the climate and
  chemical composition of the Earth are kept in
  homeostasis for long periods until some internal
  contradiction or external force causes a jump to
  a new stable state.
• Lovelocks Gaian Processes

15
Gaia Theory

• According to Dr. Lovelock
• Gaia theory predicts that the climate and
  chemical composition of the Earth are kept in
  homeostasis for long periods until some internal
  contradiction or external force causes a jump to
  a new stable state.
• Lovelocks Gaian Processes
• Oxygen levels
• Surface Temperatures
• Sea Salinity
• Carbon Burial

16
Gaia Theory

• Maintenance of Surface Temperatures
• According to Gaia, life regulates surface
  temperature because it has remained within 10-20
  C for over 3 billion years.
• It has also remained constant since life
  appeared. This is remarkable because the suns
  output has increased by 30 or 40.
• Maintenance of Oxygen Levels
• Gaia is responsible for maintaining the oxygen
  levels within the range of oxygen-breathing
  animals.
• The oxygen buildup began with the first
  appearances of eukaryotic cells.
• There has to be oxygen for ozone and that is when
  life traveled to land.

17
Gaia

• Burial of Carbon
• a constant rain of carbonate bearing shells
  sinks toward the ocean floor, where it ultimately
  forms beds of chalk or limestone rock and thus
  prevents the stagnation of carbon dioxide in the
  upper layers of the sea
• This process helps regulate the carbon dioxide
  content of the atmosphere.

18
Gaia

• Burial of Carbon
• a constant rain of carbonate bearing shells
  sinks toward the ocean floor, where it ultimately
  forms beds of chalk or limestone rock and thus
  prevents the stagnation of carbon dioxide in the
  upper layers of the sea
• This process helps regulate the carbon dioxide
  content of the atmosphere.
• Carbon to silicate conversion process (negative
  feedback process)

19
Daisyworld Experiments

• A simple mathematical model Watson and Lovelock
  (1983)
• To demonstrate the principle of biological
  homeostasis
• Automatic stabilization of a planets temperature
  in the face of increased solar luminosity through
  biological feedbacks
• Coupled vegetation-climate model subject to
  external perturbations

20
Daisyworld Experiments

• A simple mathematical model Watson and Lovelock
  (1983)
• To demonstrate the principle of biological
  homeostasis
• Automatic stabilization of a planets temperature
  in the face of increased solar luminosity through
  biological feedbacks
• Coupled vegetation-climate model subject to
  external perturbations
• Daisyworld supports the hypothesis of Gaia

21
Daisyworld

• Planet of gray colored surface with two types of
  plants black daisy and white daisy.
• Barren surface and surface covered with black or
  white daisies have different albedos.
• By natural selection, the percentage of area
  covered with black or white daisies varies.
• This varies total albedo, thus affecting global
  temperature.
• The color of daisies indicates the amount of
  surface reflection which, in turn, affects the
  Earths temperature.
• When temperature is too cold, daisy seeds cannot
  germinate.
• When temperature is too hot, all daisies die.
• The growth rates depend only on the local
  temperature.
• Local temperature in part affected by local
  albedo

22
Results from Daisyworld

• http//www.gingerbooth.com/courseware/daisy.html

23

• Activity 7 continued
• Question 6 For each value of solar luminosity
  (0.5, 0.7, 0.9, 1.1, 1,3, 1.5), sketch the
  approximate location of the black and white
  daisies and explain your answer.

24

• At the beginning of the simulation, Daisyworld is
  so cold that only a few black daisies, and almost
  no white daises, can survive. Whenever the
  planet's temperature decreases, the black flowers
  tend to predominate, they absorb a little heat
  from the sun, which causes the planet's
  temperature to rise, allowing a greater
  proliferation of black daisies, more absorption
  of heat, and so on. As the planet becomes hotter
  white daisies begin to breed as well, and
  eventually the planet reaches a point of
  temperature equilibrium. Any increase in
  temperature is combated by a greater proportion
  of white daisies any decrease leads to more
  black daisies. Such a system is remarkably stable
  against varying solar input the entire planet
  maintains homeostasis. Eventually the external
  temperature becomes too hot for the daisies to
  oppose, and heat overwhelms the planet.

25
Without Daisies
80 -
Temperature
40 -
Daisies
5 -
1 billion years
-20 -
Solar Luminosity (Time)
26
With Daisies

80 -

Temperature
40 -

Daisies

5 -

2 billion years

-20 -
Solar Luminosity (Time)
27
Results from Daisyworld

• http//www.gingerbooth.com/courseware/daisy.html

28
States of equilibrium

• An equilibrium can be stable or unstable

Feedback
Feedback
1
Stable
Unstable
Stable equilibrium
29
States of equilibrium

• An equilibrium can be stable or unstable

Feedback
Positive
Feedback
Negative
1
2
2
3
3
1
Stable
Unstable
Stable equilibrium
30
States of equilibrium

• The system may have multiple states of
  equilibrium

1
Stable to small perturbations
31
States of equilibrium

• The system may have multiple states of
  equilibrium

2
3
1
Stable to small perturbations, until a big force
perturbs the system into a new equilibrium
32
Flavors of Gaia

• Two Gaia Models
• Soft Gaia hypothesis There exists a
  co-evolution of biological, physical and chemical
  elements
• Hard Gaia hypothesis

33
Flavors of Gaia

• Two Gaia Models
• Soft Gaia hypothesis There exists a
  co-evolution of biological, physical and chemical
  elements
• Hard Gaia hypothesis All earths climate
  systems under biological control including plate
  tectonics

34
Example

• Recall the faint sun paradox Explanations
• Abiotic explanation
• Biotic explanation
• Dimethylsulfide (CH3-S-CH3) production by ocean
  phytoplankton (DMS)
• When this led to too high global temperatures,
  phytoplankton die off, thus providing a
  stabilizing, negative feedback on planetary
  temperature.
• Ocean DMS production accounts for about ½ of
  total global sulfur flux to the atmosphere

35
Example

• Recall the faint sun paradox Explanations
• Abiotic explanation
• High greenhouse gases, less clouds, more ocean
  surface area could have reduced global albedo on
  the early earth
• Biotic explanation
• Dimethylsulfide (CH3-S-CH3) production by ocean
  phytoplankton (DMS)
• causes aerosol formation, in turn reducing
  planetary albedo.
• When this led to too high global temperatures,
  phytoplankton die off, thus providing a
  stabilizing, negative feedback on planetary
  temperature.
• Ocean DMS production accounts for about ½ of
  total global sulfur flux to the atmosphere