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SUMMARY:Life\, hierarchy\, and the thermodynamic machinery of planet Earth
  - Kleidon\, A (Max-Planck-Institut)
DTSTART:20100826T090000Z
DTEND:20100826T100000Z
UID:TALK25888@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Throughout Earths history\, life has increased greatly in abun
 dance\, complexity\, and diversity. At the same time\, it has substantiall
 y altered the Earths environment\, evolving some of its variables to state
 s further and further away from thermodynamic equilibrium. For instance\, 
 concentrations in atmospheric oxygen have increased throughout Earth's his
 tory\, resulting in an increased chemical disequilibrium in the atmosphere
  as well as an increased redox gradient between the atmosphere and the Ear
 th's reducing crust. These trends seem to contradict the second law of the
 rmodynamics\, which states for isolated systems that gradients and free en
 ergy are dissipated over time\, resulting in a state of thermodynamic equi
 librium. This seeming contradiction is resolved by considering planet Eart
 h as a coupled\, hierarchical and evolving non-equilibrium thermodynamic s
 ystem that has been substantially altered by the input of free energy gene
 rated by photosynthetic life. Here\, I present this hierarchical thermodyn
 amic theory of the Earth system. I first present simple considerations to 
 show that thermodynamic variables are driven away from a state of thermody
 namic equilibrium by the transfer of power from some other process and tha
 t the resulting state of disequilibrium reflects the past net work done on
  the variable. This is applied to the processes of planet Earth to charact
 erize the generation and transfer of free energy and its dissipation\, fro
 m radiative gradients to temperature and chemical potential gradients that
  result in chemical\, kinetic\, and potential free energy and associated d
 ynamics of the climate system and geochemical cycles. The maximization of 
 power transfer among the processes within this hierarchy is closely relate
 d to the proposed principle of Maximum Entropy Production (MEP). The role 
 of life is then discussed as a photochemical process that generates substa
 ntial amounts of additional free energy which essentially skips the limita
 tions and inefficiencies associated with the trans fer of power within the
  thermodynamic hierarchy of the planet. In summary\, this perspective allo
 ws us to view life as being the means to transform many aspects of planet 
 Earth to states even further away from thermodynamic equilibrium than is p
 ossible by purely abiotic means. In this perspective pockets of low-entrop
 y life emerge from the overall trend of the Earth system to increase the e
 ntropy of the universe at the fastest possible rate. The implications of t
 he theory presented here are discussed regarding fundamental deficiencies 
 in Earth system modeling\, applications of the theory to reconstructions o
 f Earth system history\, to evaluate human impacts and regarding the limit
 s of renewable sources of free energy for future human energy demands.
LOCATION:Seminar Room 1\, Newton Institute
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