Change is an extremely huge theme in A Christmas Carol, as it was during the Victorian era. So much was changing during this time, as we see with regards to the Carol.
First, the change in Scrooge is quite apparent, as we see from his past, from his present, and from his future. It was Scrooge's past that influenced his being so miserly and mean. If you recall, he was a neglected child during one of the most beautiful family times in the year, Christmas, which explains why he considers Christmas as a "humbug." This neglect changed Scrooge. But we do see a change occurring in Scrooge when he sheds a tear upon seeing himself as a very small boy at a boarding school all alone during Christmas.
In his past, we also see how Scrooge changed from valuing people, like his sister, Fan, and his fiance, to placing his love, if you will, in money, and this change results in Scrooge losing his fiance and living a very lonely life.
And that change is very apparent in Scrooge's present, for he does not celebrate Christmas, nor does he value his nephew, Fred, very much.We also see a change in Scrooge in the present when he inquires about Tiny Tim's fate.
Finally, we see an enormous change in Scrooge when he is given a look at his future, and realizes that Tiny Tim dies, and that no one cares about his death. And change Scrooge does, for he promises to celebrate Christmas in the past, the present, and in the future; he values family again for visits Fred, and he vows to help Tiny Tim by giving Bob Cratchit a raise, but first, Scrooge instructs Cratchit to buy more coal to fuel the fire in the fireplace of his office in order for everyone who comes in to feel the warmth of human compassion and generosity once again in Scrooge.