Models of global climate warming from CO2 often frame the earth’s temperature as the consequence of a single simple physical system. Radiative balance determines temperature and CO2 perturbs that balance in the direction of warming. End of story. With, of course, an important caveat of “everything else being equal”.
The radiative physics behind this and the emission height story have been thoroughly studied and are no doubt broadly correct. But I’ve always had the feeling that this is not the whole story. Something is missing. Climate has a magnificent complexity which must surely defy reduction to a single trace gas and it’s infrared photon interactions.
But such “feelings”are hardly scientific. Add heat to a system and its temperature will increase. Change the rate of heat loss and temperature change will result. That’s physics – feelings are irrelevant.
But what if, by brushing aside complexity and emergent chaotic-nonlinear dynamics, we are overlooking a crucially important player in planetary temperature? Do we really know what determines the temperature of a planet with an atmosphere, ocean, lithosphere and biosphere? Glib answers to this question are likely to be humbled by reality.
There are many systems participating in the climate of the earth. These include as already mentioned the atmosphere, oceans, ice sheets and glaciers, and cyclical changes of the biosphere with the changing seasons. None of these are single systems but a mosaic of local subsystems across the planet’s surface. What is the combined effect of all these systems? Is it no more than the added sum of all of them together? Simply totted up, so that all we need are “climate accountants” to chase down the amounts of “carbon” and energy and their movements, and end up with a simple single number bottom line?
But what if the multiple systems participating in climate are not just serial entries in an accountant’s spreadsheet? What if they are a community that interact in emergent dynamics? If they are in a way, “alive” and responsive to each-other? This is the completely different paradigm that is presented in this paper by Bartlett and Bullock 2016: it is published in ALIFE 2016, the Fifteenth International Conference on the Synthesis and Simulation of Living Systems:
Here’s the abstract:
We demonstrate the emergence of spontaneous temperature regulation by the combined action of two sets of dissipative structures. Our model system comprised an incompressible, non-isothermal fluid in which two sets of Gray-Scott reaction diffusion systems were embedded. We show that with a temperature dependent rate constant, self-reproducing spot patterns are extremely sensitive to temperature variations. Furthermore, if only one reaction is exothermic or endothermic while the second reaction has zero enthalpy, the system shows either runaway positive feedback, or the patterns inhibit themselves. However, a symbiotic system, in which one of the two reactions is exothermic and the other is endothermic, shows striking resilience to imposed temperature variations. Not only does the system maintain its emergent patterns, but it is seen to effectively regulate its internal temperature, no matter whether the boundary temperature is warmer or cooler than optimal growth conditions. This thermal homeostasis is a completely emergent feature.
As a gross simplification, Bartlett and Bullock found that a class of systems exhibiting emergent pattern formation “preferred” a narrow temperature range, and that, if the system contained both endothermic and exothermic components, the system could engage these components actively to maintain temperature within their preferred range.
Now Bartlett and Bullock were not talking about climate. But could the community of interacting systems the authors are describing, include the climate system? It is well known that climate is dissipative. Heat enters from the sun, distributes in complex ways and never reaches equilibrium. What about multiple systems with different enthalpy? Well we know that there are excitable fluid systems that can experience excursions of positive feedback self reinforcement. Which can both warm and cool. In ocean circulation, the Atlantic Meridional Overturning Circulation (AMOC) engages a positive feedback linking salinity transport from the Caribbean to the Norwegian Sea with deep water formation and southward flow of Atlantic bottom water. This is a positive feedback that propels warming, transporting equatorial water poleward. The AMOC is the best known example but no doubt not the only such oceanic system that does this.
Then also you have the ice sheets that from time to time enter a regime of albedo positive feedback, where their expansion increases albedo with all that snowy whiteness reflecting sunlight, driving temperatures still lower and leading to an excursion of runaway cooling and abrupt glaciation. So in principle, these respective systems – ocean circulation moving warm water poleward and sea ice engaging in albedo feedback, could be described as exothermic and endothermic. One acts to warm the system and the other to cool.
There are many other components of the fantastically intricate earth system driven largely by the three phases of water in dynamic and chaotic exchange. Along with atmospheric turbulent mixing and all the multi-scale ocean mixing processes.
So in principle, the earth’s climate could be envisioned to fall into the category of systems described by Bartlett and Bullock, exhibiting emergent temperature regulation. This means that as an emergent property, the climate system would forcibly act to keep temperature within a narrow limit, and resist processes that might change temperature.
One emergent thermo-regulatory process has been identified by Willis Eschenbach, namely the process of tropical thunderstorm formation by which ocean surface heat is spontaneously ejected to space in the case where sea surface temperatures exceed about 30 degrees C.
This is a paradigm in which the demonstration that increased CO2 causes infrared atmsphere warming, would be insufficient to conclude that global climate warming would result. It is the contribution of only one part of the system, and ignores the thermo-regulatory behaviour of the system as a whole.
A much more sophisticated approach would be needed to analyse effects of perturbation of such a quasi-living system; something perhaps like attractor landscape analysis. Something way beyond the scope of current climate science. It would be a good first step to recognise that – in a way – earth’s climate is acting like a living system. More like biology, less like physics. And least of all – like the dismal science, accountancy.