In the natural world, the weather is an example of both controlled and uncontrolled variation.
| Controlled | Uncontrolled |
|---|---|
|
Rain Sunshine Wind Tides |
Tornado Drought Hurricane Floods |
In each case, the usual pattern of controlled variation (i.e. strength of the wind, height of tide) becomes subject to a Special Cause which leads to the variation becoming uncontrolled: tornadoes and hurricanes are caused by the collision between warm and cold air masses.