Lecture: June 24, 2:15 pm

Prof. Dr. Gerrit Lohmann


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Time required for each lecture: 7 h


11) Earth system models including tracers and dynamical vegetation


Learning outcome:

Earth System Models

Carbon, Radiocarbon

Tracers in the Sea

Vegetation dynamics,

Vegetation & Ecosystem models

Daisy World

I) Daisy World dynamics,
II) Green Sahara,
III) stochastic equations of the Earth system


Interactive Daisy World model


“elements of a biological feedback system which might help regulate the temperature of the Earth”

Exercise I: Interactive Daisy World model

  1. Run Daisy World with the the Daisies - black and white. Notice for what range of luminosity the daisies manage to control the planet temperature.

  2. Do you think control would be better if you set the low and high albedos (for black and white) to a wider spread?

  3. You will notice that the living area (“total daisies”) doesn’t exceed 70%. The deathrate is set to 0.3, which may explain the living percentage being no more than 0.7. What does the deathrate do to the daisies’ ability to control their environment’s temperature? To the species mix?

  4. What is the effect with no daisies for the global temperature ? This can be studied by increasing the death rate to 1.

  5. What is the influence of the optimal growth temperature? Please vary the numbers and describe the consequence !

  6. Daisyworld Model quizz

PS: here is the Python code


Exercise II: Vegetation Dynamics and the African humid period

  1. Describe the vegetation dynamics for the Holocene (8000 years ago)! Which evidences?

  2. Which feedbacks are acting in the system ?

  3. Is it possible to generate a green Sahara and Sinai under present conditions?

  4. Is this an option solving political conflicts ?



Exercise III: Random Systems

  1. Simulate the velocity evolution of one particle which is determined by the following stochastic dx/dt = -bx + kW(t)

  2. What happens if you change the timestep ?

  3. Simulate the ensemble of multiple particles and plot the time evolution of the v-distribution and compare with the diffusion equation !

  4. Test the ergodic theorem: time average is equal ensemble average !

  5. Have a look at the more complex 2D diffusion equation program. When are the two colors are mixed?



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