Neither Necessary Nor Sufficient

Abstract

Lewis examines the key scientific concept of knowability using case studies from climate science. By unpacking the ideas of a settled climate science and scientific consensus, Lewis presents the uncertain and unknown as fundamental aspects of the world. Lewis discusses two disparate understandings of causality by exploring the attribution of extreme climate events to particular causes. The first is a mathematical framework of cause and effect, while the second embraces the capacities of both the human and the nonhuman to cause important effects as actants. Lewis explores these differing conceptualisations of causality through a critical reflection on her own scientific research, her proximity to a tragedy and her personal experiences of an extreme climate event. In response to these experiences, Lewis concludes with a recommendation around scientific terminology of causality.

Glossary

Actants

 An actant is a source of action, either human or nonhuman, or both. Bruno Latour (1996, p. 7) defines it as ‘something that acts or to which activity is granted by others. It implies no special motivation of human individual actors, nor of humans in general.’ An actant is neither an object, nor a subject, but an ‘intervener.’

Agency

 The capacity to act independently.

Anthropogenic

 Changes in the environment resulting from human influences, for example, increases in greenhouse gas concentrations from industrialisation.

Extreme weather-blame question

 Following Hulme (2014, p. 2) this is ‘Was this particular weather caused by greenhouse gases emitted from human activities and/or by other human perturbations to the environment?’

Forcing

 Any influence on the climate that originates from outside the climate system itself. For example, changes in solar radiation and greenhouse gas concentrations are forcings.

Fraction of attributable risk (FAR)

 The change in risk of an event (such as a heatwave occurring) that can be attributed to particular factors (such as greenhouse gases). This value is widely used in epidemiological studies, for example, probabilistically relating the risk of lung cancer with smoking.

Knowability

 The capability of being known, apprehended and understood.

Null hypothesis significance testing (NHST)

 A statistical method used for testing whether a select factor has a statistically significant effect on an observation.

Probabilistic

 An approach or way of thinking related to probabilities. For example possible scenarios, outcomes or explanations are assessed, with each having a different degree of certainty.

Probability of necessary causation

 The probability that the event Y would not have occurred without the event X, given that both Y and X did occur. This quantifies how likely it is that X caused Y.

Probability of sufficient causation

 The probability that an event Y would have occurred in the presence of X, given that Y and X did not occur.

Sensible external world

 The idea of a world consisting of objects that exist independently of us, but can be experienced and apprehended through our senses, such as by sight and touch.

Signal/noise

 In signal processing, the noise of a system is the unwanted modifications of a signal. More generally, noise is the useless information surrounding useful information (the signal).

Significance

 A number used in statistics that expresses the likelihood that a result of an experiment could have arisen purely by chance.

Vibrant materiality

 From Bennett (2009, p. viii), referring to the capacity of the nonhuman ‘not to impede or block the will and designs of humans but also to act as quasi-agents or forces with trajectories, propensities, or tendencies of their own.’

Uncertainty

 I refer to uncertainty broadly, meaning both not knowing and also how well something is known.

Uncertainty principle

 A rule of quantum mechanics stating that the more precisely one measure of a particle is made (its position), the less precise another measurement of the same particle (its momentum) will become.