1 MET 112 Global Climate Change MET 112 Global Climate Change - Lecture 9 Daisyworld Eugene Cordero San Jose State University Outline  Introduction  Analysis  Conclusions

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 5 o C, no daisies grow,  Over 40 o C, all daisies die,  20 o C is optimal for growth of all daisies.

Imagine that the sun of Daisyworld varies from 50% to 150% of present luminosity over geologic time scales. What would happen to daisyworld during this change in solar luminosity?

Activity Answer the following questions in groups of 2 (new partner please!) 1.Plot out a graph of how you would expect the temperature of daisyworld to change as solar luminosity increases from 0.5 to 1.5 (plot, 0.5, 0.6, 0.7, 0.8, …1.4, 1.5) without any daisies on the planet. 2.Graph the temperature versus solar luminosity for daisyworld with daisies (from computer program) 3.If it takes 1 billion years for the solar luminosity to increase by 0.1, then for how many years are the daisies alive on daisyworld? 4.If daisies didn’t affect climate, then for how many years would daisies be alive on daisyworld? 5.Explain how the daisies influenced the temperature. Hint: Describe the relationship between the albedo, black daisies, white daisies and the temperature. 6.Describe the feedback processes that occur during this experiment. Hint: there may be more than one!

orld/Daisy.htm?l1=0.75&aw=0.2&ab=0.2

6 MET 112 Global Climate Change  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 earth’s surface remained in narrow range for last 3.6 billion years when heat of sun has increased by 25%?  A new theory of how the world works…

7 MET 112 Global Climate Change  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 earth’s 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%? A new theory of how the world works…

8 MET 112 Global Climate Change Answers   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:

9 MET 112 Global Climate Change 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 Sparser Vegetation, More Desertification Increased Planetary Albedo Reduced Temperature

10 MET 112 Global Climate Change What kind of feedback is this 1.Postive 2.Negative 3.Neither 4.Both Increased Planetary Temperature Sparser Vegetation, More Desertification Increased Planetary Albedo Reduced Temperature

Life collectively has a significant effect on earth’s environment Gaia Hypothesis (proposed in late 70’s) 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

Life collectively has a significant effect on earth’s environment Gaia Hypothesis (proposed in late 70’s) 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 Atmosphere-Biosphere interactions are Dominated by negative feedback Life optimizes the abiotic environment to best meet biosphere’s needs

13 MET 112 Global Climate Change A scientific twist of an ‘old idea’?   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.“ 

14 MET 112 Global Climate Change 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 (or equilibrium)

15 MET 112 Global Climate Change 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.”  Lovelock’s Gaian Processes – – – –

16 MET 112 Global Climate Change 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.”  Lovelock’s Gaian Processes –Oxygen levels –Surface Temperatures –Sea Salinity –Carbon Burial

17 MET 112 Global Climate Change Gaia Theory  Maintenance of Surface Temperatures –According to Gaia, life regulates surface temperature because it has remained within C for over 3 billion years. –It has also remained constant since life appeared. –  Maintenance of Oxygen Levels –Gaia is responsible for maintaining the oxygen levels within the range of oxygen-breathing animals. –There has to be oxygen for ozone and that is when life traveled to land.

18 MET 112 Global Climate Change Gaia Theory  Maintenance of Surface Temperatures –According to Gaia, life regulates surface temperature because it has remained within C for over 3 billion years. –It has also remained constant since life appeared. –This is remarkable because the sun’s 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. –There has to be oxygen for ozone and that is when life traveled to land.

19 MET 112 Global Climate Change 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.” –

20 MET 112 Global Climate Change 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)

21 MET 112 Global Climate Change Daisyworld Experiments  A simple mathematical model [Watson and Lovelock (1983)]  To demonstrate the principle of biological homeostasis –Automatic stabilization of a planet’s temperature in the face of increased solar luminosity through biological feedbacks 

22 MET 112 Global Climate Change Daisyworld Experiments  A simple mathematical model [Watson and Lovelock (1983)]  To demonstrate the principle of biological homeostasis –Automatic stabilization of a planet’s temperature in the face of increased solar luminosity through biological feedbacks  Daisyworld supports the hypothesis of Gaia

23 MET 112 Global Climate Change 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 Earth’s 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

24 MET 112 Global Climate Change How many years are the daisies alive on daisyworld? 1.2 billion years 2.4 billion years 3.7 billion years 4.10 billion years 0 of 250

25 MET 112 Global Climate Change Activity Question 5: If daisies were not able to influence climate, then for how many years would daisies be alive on daisyworld? 1.2 billion years 2.4 billion years 3.8 billion years 4.12 billion years

Activity Question 7: Describe the feedback processes that occur during this experiment. Hint: there may be more than one! 1.Positive 2.Negative 3.Neither 4.Both

27 MET 112 Global Climate Change – Results from Daisyworld:

Activity 8: continued Question 8: 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.

29 MET 112 Global Climate Change –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. homeostasis

30 MET 112 Global Climate Change – Results from Daisyworld:

31 MET 112 Global Climate Change  Two Gaia Models –Soft Gaia hypothesis: There exists a co- evolution of biological, physical and chemical elements –Hard Gaia hypothesis: Flavors of Gaia

32 MET 112 Global Climate Change  Two Gaia Models –Soft Gaia hypothesis: There exists a co- evolution of biological, physical and chemical elements –Hard Gaia hypothesis: All earth’s climate systems under biological control including plate tectonics Flavors of Gaia

33 MET 112 Global Climate Change 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

34 MET 112 Global Climate Change 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 (CH 3 -S-CH 3 ) 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

Solar Luminosity (Time) Temperature billion years Daisies Without Daisies

Solar Luminosity (Time) Temperature billion years Daisies With Daisies