As part of the NAMASTE project we study the global structural properties of the climate system and, more generally, of planetary atmospheres, using new diagnostic tools based on the second law of Thermodynamics as proposed by Lucarini (2009), who has found a link between the Carnot efficiency, the intensity of the Lorenz energy cycle, the entropy production and the degree of irreversibility of the climate system.

One of the main research lines concerns the study and inter-comparison of the  relevant   climate balances in complex global circulation models since these are fundamental validation metrics for their assessment. So far a broad look has been taken, going from the analysis of the meridional energy transports (Lucarini and Ragone, 2011), and entropy productions  (Lucarini et al. 2011) for the CMIP3 models and the hydrological cycle (collaboration starting with B. Liepert from NorthWest Research Associates, Redmond USA).  
The use of such diagnostic tools may be particularly useful in the  study of tipping points and climatic shifts.  The bistability properties of the Earth’s climate (warm climate vs. snowball Earth) have been explored   (Lucarini et al., 2010; Boschi et al. 2012) by varying the solar constant and the carbon dioxide concentration, showing that the two climate regimes (ice-covered and today-like) feature radical different thermodynamic properties.  In particular it is found that the loss of stability of a climate regime is accompanied by the transition to a regime featuring a less efficient climate.

Another important research line deals with the study of the properties of the entropy budget of the climate system (Fraedrich and Lunkeit, 2008) for its use and significance as a diagnostic tool.  In particular we are investigating the time and space coarse-graining properties of the entropy budget in order to understand how different time and space scales impact on the estimate of the entropy budget.  A relevant case is also the study of the thermodynamics of the large-scale eddies in the atmospheric flow in collaboration with J. Li (Canadian Center for climate modeling and analysis, Victoria, British Columbia, Canada).  This provides an example in which the material entropy production is used to give local information on the large scale processes, showing that turbulent non-linear processes in fluids may have non-diffusive behaviours associated with counter-gradient eddy-fluxes. The controversial Maximum Entropy Production conjecture also has received attention (Pascale et al., 2011; Pascale et al., 2012) and has been re-discussed in terms of the horizontal and vertical entropy production decomposition proposed by Lucarini et al. (2011).

We also are studying the circulation and thermodynamic properties of atmospheres with different rotation rates and surface exchange rates with the Planet Simulator.  This is relevant for planetary atmospheres and will allow us to test recent theoretic advancement on the thermodynamics of far-from-equilibrium systems (Lucarini, 2009).

At the moment we are starting a collaboration with P. Read and Y. Wang (University of Oxford, Department of Physics) on planetary atmospheres and with Alexander Clausius and Peter Hauschildt from Hambuger Sternwarte on exoplanetary atmospheres.

Also research on thermodynamics of electromagnetic radiation and phase change of the water components is carried out (Pelkowsky, 1994; Pelkowsky and Frisius, 2011). While the processes of absorption and emission have aroused some interest in recent times, phase changes still offer some fundamental issues waiting to be resolved. In general terms, and besides some issues regarding conceptual ambiguities, the question of the entropy production due to phase changes is being addressed at this time (on a phenomenological level). For radiation, extant theories of its irreversible character must be simplified so as to be useful in simple climate modelling. But the main goal of my activities is to have the classical framework of irreversible processes complemented with the two energetically most important exchange mechanisms within the climate system.