From the abstract we have:
A controversial hypothesis suggests that the dry and clear regions of the tropical atmosphere expand in a warming climate and thereby allow more infrared radiation to escape to space. This so-called iris effect could constitute a negative feedback that is not included in climate models. We find that inclusion of such an effect in a climate model moves the simulated responses of both temperature and the hydrological cycle to rising atmospheric greenhouse gas concentrations closer to observations.(Bold is mine.)
That is a complete understatement. Many readers will be familiar with the 'tropics troposphere of doom' such as this:
Another line of evidence that the oceans are the real climate regulator.