Tipping Point definitions as in what Earth climate change has passed- 5 dictionary takes at Heating Planet blog

American Heritage- A critical moment in a complex situation in which a small influence or development produces a sudden large or irreversible change.

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Physics- the point at which an object is no longer balanced, and adding a small amount of weight can cause it to topple. 

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Dictionary dot com- noun -the point at which an issue, idea, product, etc., crosses a certain threshhold and gains significant momentum, triggered by some minor factor or change. the point in a situation at which a minor development precipitates a crisis. Every infected person brings us closer to the tipping point, when the outbreak becomes an epidemic.First recorded in 1955–60

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CAMBRIDGE Dictionary: the time at which a change or an effect cannot be stopped: The earth has already passed the tipping point in terms of global warming. 

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OXFORD: ​the point at which the number of small changes over a period of time reaches a level where a further small change has a sudden and very great effect on a system or leads to an idea suddenly spreading quickly among a large number of people- The technology has reached a tipping point.

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Britannica does not have it -ke