In select places on Area51 you can see your total reputation, and on each SE site you can see a temporal graph of your reputation for that site. Is there any way to see a temporal graph of your total reputation across all sites?
You can see a graph of you reputation on all sites where you have over 200 reputation from your global Stack Exchange profile:
This one's mine, but you get the idea.
This is certainly possible from a purely technical standpoint, but I doubt that implementing it would be worth the effort it would take. The "combined flair" can be fun to look at — wow, look how much bigger that number is than any of my individual site reputations! — but it doesn't have a huge amount of meaning.
Stack Overflow reputation points and Seasoned Advice reputation (and rep from other sites) are like apples and oranges (and bananas and hawthorns and mangoes and pitayas). It's hard enough to compare two apples to each other, let alone two crates of mixed fruit.
Going from a simple total sum to a graph just adds more information that has little actual significance.