According to jisho.org, they all have the same meanings, to climb, to rise, to ascend. Is that true? And do they have differences in usage?
They do have differences in usage. I've gathered a few examples that, I hope, differentiate the meanings. First, I'll try to put them in English:
But I don't know how helpful that is. Certainly there isn't a one-to-one mapping between those English words and those ways of writing のぼる. I think you'll get a better sense of what each one means if you look at how they're used:
上る Go up
昇る Ascend, rise
For more examples, see the following links:
There are several words with a series of kanji like this. There is usually a common kanji used for the basic verb, in this case のぼる which is usually 登る.
The others becomes more clear in kanji compounds. When using jisho.org, search for kanji details, then click on "words containing" and look for what sorts of compounds the particular kanji is used in.