There is a Neils Bohr aphorism - 'prediction is very difficult, especially if it's about the future'.  Climate is a 'cascade of powerful mechanisms' that is characterised by abrupt, rapid, frequent and sometimes extreme change:    classic behaviour of a dynamic and complex system in chaos theory.  The limits of predictability of climate may be much broader than we think.     

  

‘Researchers first became intrigued by abrupt climate change when they discovered striking evidence of large, abrupt, and widespread changes preserved in paleoclimatic archives. Interpretation of such proxy records of climate - for example, using tree rings to judge occurrence of droughts or gas bubbles in ice cores to study the atmosphere at the time the bubbles were trapped -is a well-established science that has grown much in recent years. This chapter summarizes techniques for studying paleoclimate and highlights research results. The chapter concludes with examples of modern climate change and techniques for observing it. Modern climate records include abrupt changes that are smaller and briefer than in paleoclimate records but show that abrupt climate change is not restricted to the distant past.’
US National Academy of Science, Committee on Abrupt Climate Changes (2002), Abrupt Climate Change: Inevitable Surprises NAP – p19

Abrupt climate change, and its theoretical underpinning in complex systems theory, are not new ideas but are not ones that have permeated the zeitgeist deeply.  Somewhat like Einstein’s Special Theory of Relativity – it is counterintuitive and demands nothing less than a complete overturning of the way we think.  Judging by the continued dominance of the arrow of time concept in public expressions – Einstein’s thoughts about space and time has likewise not permeated deep into the zeitgeist in 100+ years.  A complex systems metatheory of climate is not incremental knowledge.  It doesn’t add to the pool of knowledge about climate.  Rather, it reveals fundamental properties of climate that completely invalidate conventional thinking.  It is somewhat more important than relativity theory, given the short and medium term implications for human societies, that the dynamical and complex systems metatheory of climate is understood more widely and an abrupt paradigm shift occur in climate science.      

We are given to thinking in terms of simple cause and effect analogous to a crowbar on a fulcrum.  Push at one end and there is a defined and linear change at the other.  Thus, if we add X amount of carbon dioxide there will Y amount of warming.  Thinking in terms of simple cause and effect, linear climate thinking, is embodied in the climate sensitivity formula:

∆T_s =   λ. RF                                                             

Where:              ∆T_s is the change in surface temperature;
                         λ is the climate sensitivity constant;
                         and RF is the radiative forcing from greenhouse gases.

 Climate reality is that abrupt and nonlinear climate change is the norm and the dynamic sensitivity formula must have the form:

 DT_s/Dt = Ʃ∆RF. F(X₁, X₂, X₃,…, X _n)         

 Where: DT_s/Dt is the change in surface temperature over time;

 ∆RF are changes in radiative forcing from any source; and

 X_1… X_n are nonlinear (and dynamic) climate sub-system responses.        

The meaning of the revised formulation is that small changes in radiative forcing, from changes in solar activity, orbital wobbles and atmospheric composition, push climate past threshold points triggering large fluctuations in ice and cloud cover, heat transport, dust, changes in the polar vortices, variations in surface and deep ocean currents and changes in wind, ocean upwelling and precipitation modifying ecologies globally along with Earth albedo.  Abrupt climate change is theoretically determinant but practically incalculable.       

Abrupt climate change occurs on all scales from interannual ENSO events, to decades, ice ages and beyond.   More important than the detail of specific abrupt climate changes is in understanding the principle in mathematical physics of abrupt change and applying it as a fundamental property of climate. 

Abrupt change is not unusual in systems as diverse as the human heart, nervous systems, ant colonies, global economies or whole ecologies.  Many physical (and social) systems exhibit abrupt (so called chaotic) changes. Weather has been known to be ‘chaotic’ since the 1960’s.  All these systems share properties that are defined in terms of complex systems theory.  Chief amongst these commonalities is that the systems are sensitive to small initial changes – the so called butterfly effect.  Complex systems theory is a metatheory, a theory of theories, under which umbrella climate science is now to be located along with other dynamic and complex systems.