Conventionally, the latitudes between 23.5oN (the Tropic of Cancer) and 23.5oS (the Tropic of Capricorn), the most northerly and southerly latitudes at which the sun is directly overhead in midsummer (21 June and 21 December respectively). The tropics, alternatively defined as those latitudes creating global-scale updraughts, are expanding by up to 1o of north and south latitude per decade owing to climate change, and the associated tropical storms are reaching their maximum intensity 52–63km further north and south every decade.

This definition is abridged from A – Z of tree terms: A companion to British arboriculture.
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