Daisyworld Lab

Students explore Daisyworld, a model of a self-regulating system incorporating positive and negative feedbacks. Daisyworld is a planet on which black and white daisies are the only things growing. The model explores the effect of a steadily increasing solar luminosity on the daisy populations and the resulting planetary temperature. The growth function for the daisies allows them to modulate the planet's temperature for many years, warming it early on as radiation absorbing black daisies grow, and cooling it later as reflective white daisies grow. Eventually, the solar luminosity increases beyond the daisies' capability to modulate the temperature and they die out, leading to a rapid rise in the planetary temperature. Daisyworld was conceived of by Andrew Watson and James Lovelock to illustrate how life might in part have been responsible for regulating Earth's temperature as the Sun's luminosity increased over time. This exercise guides students through some of the mathematics behind the modeling, and uses STELLA or Fortran 90 code.