The iris hypothesis is a theory proposed by Prof. Richard Lindzen in 2001 [1] that suggested increased sea surface temperature in the tropics would result in reduced cirrus clouds and thus more infrared radiation leakage from Earth's atmosphere. This suggested infrared radiation leakage was hypothesized to be a negative feedback which would have an overall cooling effect. The consensus view is that increased sea surface temperature would result in increased cirrus clouds which would have the effect of warming the sea surface further and thus there would be positive feedback.
Other scientists have since tested the hypothesis. Some concluded that that there was simply no evidence supporting the hypothesis [2]. Others found evidence suggesting that increased sea surface temperature in the tropics did indeed reduce cirrus clouds but found that the effect was nonetheless a positive feedback rather than the negative feedback that Lindzen had hypothesized [3][4]. However, there has been some relatively recent evidence potentially supporting the hypothesis [5].
