Chapter 3 Daisyworld Objectives Albedo Couplings between daisy

Chapter 3 Daisyworld Objectives: • Albedo • Couplings between daisy coverage & T • Equilibrium states in Daisyworld • Response of Daisyworld to incr. solar output ENSC 425/625 Chapter 3 UNBC 1

A view of Daisyworld from outer space ENSC 425/625 Chapter 3 UNBC 2

ENSC 425/625 Chapter 3 UNBC 3

Couplings between daisy coverage & T • Incr. daisy coverage of planet => decr. T. T Daisy coverage Daisy Coverage albedo Daisy Coverage T T ENSC 425/625 Chapter 3 UNBC 4

• Daisies can live between a min. T & a max. T daisy coverage Daisy coverage T T daisy coverage optimum min. ENSC 425/625 Chapter 3 UNBC max. T 5

• Intersection of 2 curves means the 2 effects are balanced => equilibrium points P 1 & P 2. Daisy coverage T daisy coverage T Effects of daisy coverage on T P 1 Effects of T on daisy coverage P 2 T ENSC 425/625 Chapter 3 UNBC 6

Daisy coverage Feedback loops Effects of daisy coverage on T Effects of T on daisy coverage P 1 P 2 T ENSC 425/625 Chapter 3 UNBC 7

• Perturb daisy coverage at P 1 => sys. returns to P 1 Daisy coverage (stable equil. pt. ) P 1 A large perturb. => daisies all die from extreme T P 2 T ENSC 425/625 Chapter 3 UNBC 8

• Large incr. in daisy cover => very low T => Daisy coverage decr. in daisy cov. => very high T => lifeless. P 1 P 2 T ENSC 425/625 Chapter 3 UNBC 9

• From P 2, incr. daisy cov. => decr. T => Daisy coverage further incr. in daisy cov. => converge to P 1 daisy T coverage P 1 unstable P 2 equilib. pt. T ENSC 425/625 Chapter 3 UNBC 10

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Daisy coverage Gradual incr. in solar luminosity For any particular value of daisy cov. , T incr. P 1 The effect of T on Daisy unchanged P 1 To Teq P 2 Tf ENSC 425/625 Chapter 3 UNBC P 2 T 12

• As solar lum. % daisy cov. incr. , T incr. => daisy cov. incr. • Eventually, daisies cannot expand, but T keeps incr. => daisies dying => decr. albedo => rapid T incr. (pos. feedback) => daisies extinct. T Min. T for daisy survival Max. T for daisy survival Solar luminosity ENSC 425/625 Chapter 3 UNBC 13

Lessons from Daisyworld • Despite change in forcing, climate sys. can counter part of the change by negative feedback loops. ENSC 425/625 Chapter 3 UNBC 14