From greenhouse to hothouse: the language of climate change

Feedback effects could spark irreversible global warming, says scientists. But what does the word ‘hothouse’ imply?

Scientists warned this week that feedback effects in global warming might tip the Earth into a “hothouse state”, recovery from which could be impossible, even by reductions in CO2 emissions. How frightened should we be about moving from a greenhouse to a hothouse?

The mechanism by which atmospheric gases warm the planet has been well understood since the 19th century. High CO2 levels early in the Earth’s history, wrote the geologist Thomas Sterry Hunt in 1867, had created the sort of climate that would have resulted if we “had covered the Earth with an immense dome of glass, had transformed it into a great orchid house”. The term “greenhouse effect” was coined in 1907.

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