Single Cause
Also: Single Cause
Logical Fallacy: Single Cause
Assuming a single cause or reason when there might be multiple causes or reasons.
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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.