WEBVTT FILE

1
00:00:00.000 --> 00:00:04.040
Picture a simple theoretical planet. Simpler.

2
00:00:04.059 --> 00:00:08.070
Simpler. Keep, keep going, keep--nope that's

3
00:00:08.090 --> 00:00:12.110
too far. That is just a dot. Not even trying. Ok,

4
00:00:12.130 --> 00:00:16.130
there. This is DaisyWorld, a place where only two things

5
00:00:16.149 --> 00:00:20.150
live: black daisies and white daisies.

6
00:00:20.170 --> 00:00:24.170
In the early days, the atmosphere of DaisyWorld

7
00:00:24.190 --> 00:00:28.190
is cooler and black daisies thrive in these cooler temperatures.

8
00:00:28.210 --> 00:00:32.200
The black daisy population does so well in fact

9
00:00:32.220 --> 00:00:36.250
that it absorbs more energy and begins the warm the little planet.

10
00:00:36.270 --> 00:00:40.290
But now it's too warm for black daisies, but it's just right for the white

11
00:00:40.310 --> 00:00:44.390
daisies to blossom and expand. And while the planet is covered with

12
00:00:44.410 --> 00:00:48.429
more and more white daisies, they begin to reflect more energy back

13
00:00:48.450 --> 00:00:52.460
into space. We call this amount of reflectance albedo. The more reflective

14
00:00:52.480 --> 00:00:56.480
the surface of the planet, the higher its albedo. We can think of it

15
00:00:56.500 --> 00:01:00.519
as a percentage of how much energy is coming in and then bouncing back out

16
00:01:00.540 --> 00:01:04.539
into space. For instance, the albedo of a perfect mirror would

17
00:01:04.560 --> 00:01:08.570
be one hundred percent. If we had a completely

18
00:01:08.590 --> 00:01:12.680
black surface the albedo would be zero percent.

19
00:01:12.700 --> 00:01:16.720


20
00:01:16.740 --> 00:01:20.759
Or a waterworld, that could be twenty percent.

21
00:01:20.780 --> 00:01:24.800
Now the white daisies cool the planet again,

22
00:01:24.820 --> 00:01:28.839
and that makes it more favorable for black daisies to thrive once again.

23
00:01:28.860 --> 00:01:32.900
Now we're back to where we started. The black daisies have taken over

24
00:01:32.920 --> 00:01:36.950
but they'll warm up the planet, and then they'll die and the white daisies will grow

25
00:01:36.970 --> 00:01:41.000
but then they'll reflect more heat back out and then they'll die and on and on and on and back

26
00:01:41.020 --> 00:01:45.020
and forth.

27
00:01:45.040 --> 00:01:49.050
And over time, within a narrowly defined temperature range,

28
00:01:49.070 --> 00:01:53.070
DaisyWorld stays resilient and makes it possible for daisies to exist

29
00:01:53.090 --> 00:01:57.090
at all. Of course, this is a theoretical planet; there are no

30
00:01:57.110 --> 00:02:01.110
variables, like rotation, seasons,

31
00:02:01.130 --> 00:02:05.119
diseases,

32
00:02:05.140 --> 00:02:09.169
geography, or even humans.

33
00:02:09.190 --> 00:02:13.210
It does illustrate how a change in one environmental condition

34
00:02:13.230 --> 00:02:17.250
can cause a change in a second condition, which in turn, can change the first condition

35
00:02:17.270 --> 00:02:21.280
again. We call this a feedback loop.

36
00:02:21.300 --> 00:02:25.310
The DaisyWorld model is an example of a negative feedback

37
00:02:25.330 --> 00:02:29.340
loop because the initial changes to the climate are muted by the combination

38
00:02:29.360 --> 00:02:33.370
of black and white daisies. On Earth

39
00:02:33.390 --> 00:02:37.390
we can see this kind of negative feedback loop with clouds. Let's say

40
00:02:37.410 --> 00:02:41.400
increasing temperatures cause more surface evaporation, which cause more

41
00:02:41.420 --> 00:02:45.459
cloud formation, and clouds, much like our white daisies, have a

42
00:02:45.480 --> 00:02:49.510
higher albedo than the Earth's surface. Then the clouds will

43
00:02:49.530 --> 00:02:53.540
reflect more heat and cool the planet. When we look at snow

44
00:02:53.560 --> 00:02:57.570
and ice at the poles, which have a high albedo, we can see a positive

45
00:02:57.590 --> 00:03:01.610
feedback loop. When temperatures rise, the snow and ice

46
00:03:01.630 --> 00:03:05.630
melt, and so even more energy is absorbed by the water, and this

47
00:03:05.650 --> 00:03:09.640
continues to melt the snow and ice even further. With increasing climate change

48
00:03:09.660 --> 00:03:13.660
the natural reflectance of our icy poles dramatically declines.

49
00:03:13.680 --> 00:03:17.670
DaisyWorld is a much simpler place than our own planet,

50
00:03:17.690 --> 00:03:21.730
but it shows us that maintaining a population on Earth requires a

51
00:03:21.750 --> 00:03:25.780
delicate balance with the right organisms and the right range of

52
00:03:25.800 --> 00:03:29.800
environmental conditions.

53
00:03:29.820 --> 00:03:33.820


54
00:03:33.840 --> 00:03:37.850
Beep, beep.

55
00:03:37.870 --> 00:03:41.880


56
00:03:41.900 --> 00:03:46.340