A new public alerting scheme for terrorism was introduced in Australia this week, with the 5 color-coded levels shown here. The previous scheme, introduced in 2003, had 4 levels (low, medium, high and extreme), primarily reflecting the scale or severity of the threat. The new scheme's levels primarily reflect the probability of an attack.
I'm puzzled because, as generally understood, risk reflects both aspects - the likelihood, probability or chance of an incident coupled with its scale, severity, consequences or impact.
With the new system, even if a threat is deemed "certain" and coded red, the scale gives us no idea of the likely scale of the incident/s. Are we talking about a lone gunman on the rampage in one location, a coordinated series of attacks across a number of locations, or what?
Perhaps I should suggest the Analog Risk Assessment method to the Australian government.