Jones, Roger ORCID: 0000-0001-6970-2797 (2015) Reconciling anthropogenic climate change and variability on decadal timescales: history and philosophy. Working Paper. VISES, Victoria University, Melbourne, Australia.

Abstract

How the climate changes on decadal timescales can be described by two alternative hypotheses: 1) externally forced climate change is gradual and linear within a background of random variability and 2) the two phenomena interact, producing a distinct nonlinear response. Current methods for analysing and communicating climate change self‐select the linear hypothesis. This is characterised by linear trends applied within a signal to noise model and is communicated through a scientific narrative that describes climate change as being gradual. Theory and a growing set of observations support the nonlinear hypothesis, suggesting that decadal scale climate change is episodic, exhibiting nonlinear complex system behaviour. Scientific paradigms are a mix of methods, theory and scientific values that evolve at different rates. This paper examines how the gradualist paradigm arose, why nonlinear phenomena are treated as noise despite being a fundamental part of the climate system and why it has taken over 50 years since Lorenz’ discovery of fundamentally nonlinear behaviour for the gradualist paradigm to be seriously challenged. Linear methods and their supporting cognitive values trace back to the scientific enlightenment. Uniformitarianism and gradualism began as cosmological values within the earth sciences, later evolving into cognitive values that underpinned the development of the signal‐to‐noise model. The recent attacks on climate science by political and vested interests have discouraged mainstream climate science from openly investigating theoretical alternatives to the status quo. While other areas of the physical and natural sciences have moved to explicitly represent complex system behaviour, climatology is the last branch of the earth sciences to do so.

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