NARRATOR:
Picture a simple theoretical planet.
Real footage of the earth from space.
NARRATOR:
Simpler.
An accurate drawing of the earth, showing the green of vegetation, brown of deserts and blue of the oceans.
NARRATOR:
Simpler.
A plastic blow-up globe of the earth bounces on the floor.
NARRATOR:
Keep... keep going.
A childlike sketch of the earth, then, finally, a simple round blue dot.
NARRATOR:
Nope, that's too far, that is. That is just about... not even trying. OK, there.
Shot of a plasticine brown planet, covered with equal amounts of black and white plasticine daisies.
NARRATOR:
This is Daisy World, a place where only two things live - black daisies and white daisies. In the early days, the atmosphere of Daisy World is cooler and black daisies thrive in these cooler temperatures. The black daisy population does so well, in fact, that it absorbs more energy and begins to warm the little planet.
Sun rays blast into the planet and are absorbed by the growing population of black daisies.
NARRATOR:
But now it's too warm for black daisies but it's just right for the white daisies to blossom and expand. And while the planet is covered with more and more white daisies, they begin to reflect more energy back into space. We call this amount of reflectance 'albedo'.
Sun rays bounce off the growing population of white daisies.
NARRATOR:
The more reflective the surface of the planet, the higher its albedo. We can think of it as a percentage of how much energy is coming in and then bouncing back out into space. For instance, the albedo of a perfect mirror would be 100%. If we had a completely black surface, the albedo would be 0%. Or a water world, that could be 20%. Now, the white daisies cool the planet again and that makes it more favourable for black daisies to thrive once again. Now we're back to where we started. The black daisies have taken over, but they'll warm up the planet and then they'll die and the white daisies will grow, but then they'll reflect more heat back out and then they'll die, and on and on and on and back and forth.
Shot of a line graph. The X-axis is labelled 'Solar Input', the Y-axis 'Temperature'. A red line rises up at a 45-degree angle from where the axes meet. From halfway up the red line, it is labelled 'no daisies'. A purple line is drawn, looping up from a low temperature to about midway on the Y-Axis where it crosses the red line and continues horizontally across. After this intersection, it is labelled 'with daisies'. Black and white daisies sprout up along the purple line.
NARRATOR:
And over time, within a narrowly defined temperature range, Daisy World stays resilient and makes it possible for Daisies to exist at all. Of course, this is a theoretical planet. There are no variables, like rotation, seasons, diseases, geography, or even humans. It does illustrate how a change in one environmental condition can cause a change in a second condition which, in turn, can change the first condition again. We call this a 'feedback loop'. The Daisy World model is an example of a negative feedback loop because the initial changes to the climate are muted by the combination of black and white daisies. On Earth, we can see this kind of negative feedback loop with clouds. Let's say increasing temperatures cause more surface evaporation which cause more cloud formation. And clouds, much like our white daisies, have a higher albedo than the earth's surface.
Clouds form over plasticine mountains. Rays of sunlight strike the clouds and bounce off back into space.
NARRATOR:
Then the clouds will reflect more heat and cool the planet. When we look at snow and ice at the poles, which have a high albedo, we can see a positive feedback loop.
A plasticine model of the North Pole from space. Sun rays strike the white ice and reflect back into space.
NARRATOR:
When temperatures rise, the snow and ice melt and so even more energy is absorbed by the water, and this continues to melt the snow and ice even further.
The ice of the North Pole retreats until almost all of the sun rays are being absorbed into the water.
NARRATOR:
With increasing climate change, the natural reflectance of our icy poles dramatically declines. Daisy World is a much simpler place than our own planet. But it shows us that maintaining a population on Earth requires a delicate balance with the right organisms and the right range of environmental conditions.
End credits - 'Additional footage courtesy of pond5.com, FootageFirm.com.' A satellite flies beside the earth. Text on screen - 'NASA Goddard Space Flight Center. www.nasa.gov/goddard'.