1700s
Over the years Carlisle had become Aro's main confidant. He had told him about everything excluding the circumstances of Didyme's death and Bella's time as a member of the Volturi. In return Carlisle shared all his hopes and dreams with Aro.
Carlisle was set on the idea of going to see Bella, despite Aro's pleading. Aro knew that if Carlisle saw with his own eyes how the world had advanced while he was cooped up in the Volturi castle reading that he'd want to finally set out on his own.
"You must visit us soon, Carlisle." Caius said, figuring he wouldn't be coming back for at least two centuries, despite all the bribes Aro was trying to give Carlisle to make him come back. He was close to having Chelsea bind him to the Volturi, but he didn't want to force his friendship with Carlisle.
Aro was mainly worried about Carlisle's hope of rejoining Bella and work as a doctor on her territory. If Bella accepted him as part of her coven then due to his deal with her he'd never be able to talk to him again.
Of course he couldn't tell Carlisle this though. That would just lead to questions that Aro would rather not have to deal with.
So with much sadness Aro bid farewell to Carlisle.
Sad time for Aro.