1 met 112 global climate change met 112 global climate change - lecture 9 daisyworld eugene cordero...

1 MET 112 Global Climate MET 112 Global Climate ChangeChange

MET 112 Global Climate Change - Lecture 9

Daisyworld

Eugene CorderoSan 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 EarthSun 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 rightEnvironment 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.

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!

http://cs.clark.edu/~mac/physlets/DaisyWorld/Daisy.htm?l1=0.75&aw=0.2&ab=0.2





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…


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


What kind of feedback is this

Postiv

e

Negat

ive

Neith

erBot

h

100%

0%0%0%

1. Postive

2. Negative

3. Neither

4. Both

Increased Planetary

Temperature

Sparser Vegetation, More Desertification

Increased Planetary Albedo

Reduced Temperature

Life collectively has a significanteffect on earth’s environment

Gaia Hypothesis(proposed in late 70’s)

Goes beyond simple interactions amongst biotic and

abiotic factorsEvolution of life and Evolution of

its environment are intertwined

Biosphere can be modeled as asingle giant organism

Atmosphere-Biosphere interactions areDominated by negative feedback

Life optimizes the abiotic environmentto best meet biosphere’s needs


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)


Gaia Theory

According to Dr. LovelockAccording to Dr. Lovelock– ““Gaia theory predicts that the climate and chemical Gaia theory predicts that the climate and chemical

composition of the Earth are kept in homeostasis for long composition of the Earth are kept in homeostasis for long periods until some internal contradiction or external force periods until some internal contradiction or external force causes a jump to a new stable state.”causes a jump to a new stable state.”

Lovelock’s Gaian ProcessesLovelock’s Gaian Processes– Oxygen levels Oxygen levels – Surface Temperatures Surface Temperatures – Sea Salinity Sea Salinity – Carbon BurialCarbon Burial


Gaia Theory

Maintenance of Surface TemperaturesMaintenance of Surface Temperatures– According to Gaia, life regulates surface temperature According to Gaia, life regulates surface temperature

because it has remained within 10-20 C for over 3 billion because it has remained within 10-20 C for over 3 billion years. years.

– It has also remained constant since life appeared. It has also remained constant since life appeared. – This is remarkable because the sun’s output has increased This is remarkable because the sun’s output has increased

by 30% or 40%.by 30% or 40%.

Maintenance of Oxygen LevelsMaintenance of Oxygen Levels– Gaia is responsible for maintaining the oxygen levels Gaia is responsible for maintaining the oxygen levels

within the range of oxygen-breathing animals. within the range of oxygen-breathing animals. – There has to be oxygen for ozone and that is when life There has to be oxygen for ozone and that is when life

traveled to land.traveled to land.


Gaia

Burial of CarbonBurial of Carbon– “…“…a constant rain of carbonate bearing shells sinks toward a constant rain of carbonate bearing shells sinks toward

the ocean floor, where it ultimately forms beds of chalk or the ocean floor, where it ultimately forms beds of chalk or limestone rock and thus prevents the stagnation of carbon limestone rock and thus prevents the stagnation of carbon dioxide in the upper layers of the sea…”dioxide in the upper layers of the sea…”

– ““This process helps regulate the carbon dioxide content of This process helps regulate the carbon dioxide content of the atmosphere.” the atmosphere.”

– Carbon to silicate conversion process (negative feedback Carbon to silicate conversion process (negative feedback process)process)


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


How many years are the daisies alive on daisyworld?

25% 25%25%25%1. 2 billion years

2. 4 billion years

3. 7 billion years

4. 10 billion years

0 of 250


Activity Question 5: If daisies were not able to influence climate, then for how many years would daisies be alive on daisyworld?

0% 0%0%

100%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!

Positi

ve

Negat

ive

Neith

erBot

h

0% 0%0%

100%1. Positive

2. Negative

3. Neither

4. Both


– http://www.gingerbooth.com/courseware/daisy.html

Results from Daisyworld:

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

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


– 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.

http://www.wikipedia.org/wiki/Homeostasis


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

Solar Luminosity (Time)

Tem

pera

ture

5 -

-20 -

40 -

80 -

4 billion years

Daisies

Without Daisies

Solar Luminosity (Time)

Tem

pera

ture

5 -

-20 -

40 -

80 -

7 billion years

Daisies

• •

• • • •

• • •

• • • •

With Daisies

1 met 112 global climate change met 112 global climate change - lecture 9 daisyworld eugene cordero...

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