How does the character of Scrooge change throughout the story?

In the beginning of A Christmas Carol, Ebenezer Scrooge  has not much to offer humanity except for his word.

  "And Scrooge's name was good upon 'Change, for anything he chose to put his hand to."

He is described as a cold man with hardened features who shared little and hung onto every penny.  He kept to himself, had no friends, and attended no social events.

"But he was a tight-fisted hand at the grindstone, Scrooge! a squeezing, wrenching, grasping, scraping, clutching, covetous, old sinner! Hard and sharp as flint, from which no steel had ever struck out generous fire; secret, and self-contained, and solitary as an oyster."

His clerk is kept with a small fire in a dismal office.  He wishes Scrooge a Merry Christmas but Scrooge rebukes his attention. 

Marley's ghost visits telling Scrooge that three spirits will visit him.  Scrooge attends different times in his life with the spirits.  He is scared that if he does not change he will be the alone and not at all missed old man he had seen in the future.  When he realizes it is Christmas morning he begins to feel joy.  He had not experienced joy in many years.

"Really, for a man who had been out of practice for so many years, it was a splendid laugh, a most illustrious laugh. The father of a long, long line of brilliant laughs."