Comment on Nonequilibrium thermodynamics and maximum entropy production in the Earth system by Chief Hydrologist

Hi Everybody -

Non-equilibrium thermodynamics is a fundamental description of the Earth system and can be captured in a simple 1st order difference calculation.

dS/dt = Ein/s – Eout/s – where dS/dt is the change in energy storage in the system and Ein/s and Eout/s are the average energies into and out of the system over a period.

Within the simple global overview are of course myriad – and powerful – processes through which energy cascades in the deterministically chaotic system that is the fundamental mode of operation of Earth’s climate.

ENSO is a sub-system that is itself deterministically chaotic. The intensity and frequency of ENSO events varies at least over at least 11 millennia that we know of – http://s1114.photobucket.com/albums/k538/Chief_Hydrologist/?action=view&current=ENSO11000.gif

We are used to thinking of the oceans as layer of warm water over cold water separated by the thermocline – the depth at which the rate of decrease of temperature with increase of depth is the largest. In terms of energy dynamics – this seems relatively arbitrary. The oceans heat as a whole and cool as a whole – but within this there are hydrodynamical and atmospheric processes that influence both local and average rates of warming or cooling. ENSO is a key process involving upwelling in the eastern Pacific in a La Niña and – when the trade winds falter – the flow eastward of a pool of warm water that had been piled up against Australia and Indonesia.

The cold surface of the central Pacific in a La Niña loses less heat than the warm surface in an El Niño – remembering the net direction of energy flux. There are in addition cloud feedbacks in ENSO that again change the planetary energy dynamic.

There are 2 lessons in this. First – that energy flux is complex and dynamic and that a maximum entropy principle tells us little about specific dissipation pathways. The specific and complex pathways cannot be neglected in simplifying assumptions without catastrophic loss of verisimilitude

Secondly – that a La Niña cools the planet and an El Niño warms the planet – suggesting both a contribution to warming between 1977 and 1998 and a cooling influence for 20 to 40 years from 1998. Unless we can get this from an equation of maximum entropy – we are as far from the truth as ever.

Cheers
Robert I Ellison