John said:

> in a 2nd-order phase transition (like the point where the difference between the liquid and gas phases of water ceases to exist), a physical system becomes scale-invariant.

I've been reading about the [Walker circulation](http://en.wikipedia.org/wiki/Walker_circulation), where it says "When the Walker circulation weakens or reverses, an El NiƱo results". Does that sort of change - a change in the number of convection cells in a volume of fluid - count as a 2nd-order phase transition?