Complex sentence: Lindzen hypothesized that the Earth may act like an infrared iris; increased sea surface temperature in the tropics would result in reduced cirrus clouds and thus more infrared radiation leakage from Earth's atmosphere.
Split into simpler sentences: Lindzen hypothesized that the Earth may act like an infrared iris. A sea surface temperature increase in the tropics would result in reduced cirrus clouds and thus more infrared radiation leakage from Earth's atmosphere.