On Saturday, 30 January 2016 00:06:57 UTC, Martin Dixon wrote:

As an engineer with an understanding of system dynamics I have
commented elsewhere about the effects of feedback. But all I need to
say here is that positive feedback causes instability which the
behaviour of the earths climate system has never demonstrated. The
climate has shown itself to be remarkably stable over millions of
years, indicating that any feedback mechanisms must be predominantly
negative.

As an engineer with an understanding of system dynamics, and having taken Open University courses in geology, I can assure you that the Earth's climate system has shown severe examples of instability. During the current Holocene inter glacial the climate has been relatively stable, but that was preceded by the Younger Dryas stadial when temperatures in the Northern hemisphere returned to ice age conditions in less than 30 years. When the YD ended, temperatures rose by 20 C in Greenland in an event which may have lasted only three years long!

These facts are unbelievable but true.

My OU geology lecturer did not know the difference between negative and positive feedbacks, and there is the problem. The geologists think that the YD was caused by an event, Lake Agassiz flowing into the North Atlantic and halting the ocean currents. But why did the YD end suddenly? Did Lake Agassiz suddenly refill?

From a systems POV, these events were caused by the action of a positive feedback which can act just as abruptly in both directions. The system will remain stable until a tipping point is passed and the positive feedbacks take over. Note, that we are talking about an abrupt change so we will have no warning. Larry will be able to cry out "Where is this disaster?" until it happens!

As an engineer you only deal with systems which are designed to be stable. But the Earth system was not designed by a competent system engineer.