John Michael Greer, communicating articulately about perturbations to complex systems (read: climate) at The Archdruid Report:
The next time you fill a bathtub, once you’ve turned off the tap, wait until the water is still. Slip your hand into the water, slowly and gently, so that you make as little disturbance in the water as possible. Then move your hand through the water about as fast as a snail moves, and watch and feel how the water adapts to the movement, flowing gently around your hand. .
Once you’ve gotten a clear sense of that, gradually increase the speed with which your hand is moving. After you pass a certain threshold of speed, the movements of the water will take the form of visible waves—a bow wave in front of your hand, a wake behind it in which water rises and falls rhythmically, and wave patterns extending out to the edges of the tub. The faster you move your hand, the larger the waves become, and the more visible the interference patterns as they collide with one another.
Keep on increasing the speed of your hand. You’ll pass a second threshold, and the rhythm of the waves will disintegrate into turbulence: the water will churn, splash, and spray around your hand, and chaotic surges of water will lurch up and down the sides of the tub. If you keep it up, you can get a fair fraction of the bathwater on your bathroom floor, but this isn’t required for the experiment! Once you’ve got a good sense of the difference between the turbulence above the second threshold and the oscillations below it, take your hand out of the water, and watch what happens: the turbulence subsides into wave patterns, the waves shrink, and finally—after some minutes—you have still water again.
This same sequence of responses can be traced in every complex system, governing its response to every kind of disturbance in its surroundings…
… Once things begin to oscillate, veering outside usual conditions in both directions, that’s a sign that the limits to resilience are coming into sight, with the possibility of chaotic variability in the planetary climate as a whole waiting not far beyond that. We can fine-tune the warning signals a good deal by remembering that every system is made up of subsystems, and those of sub-subsystems, and as a general rule of thumb, the smaller the system, the more readily it moves from local adjustment to oscillation to turbulence in response to rising levels of disturbance.