@Japrim - That's a speculation with some good points. Then again, a lot also depends on how you go about changing the past.
For instance, maybe it wasn't intended for a certain time traveler to be visible in a certain place at a certain time. If that time traveler makes a physical presence there and says and/or does things he/she wasn't supposed to do at that place and time, contrary to the way the past went before, then I could see catastrophe possibly arising.
However, I think that if that time traveler were to make his/her self invisible in that certain place and time, and use the power of the mind to influence and/or change the actions of people involved in that particular place and time, things would go much more smoothly without catastrophic consequences.
As I go about my own journey in changing things in the past, I'd prefer using mind power, anyway. I can see myself using some sort of mind control helmet, something
@Genius has brought up several times on this site.
In a nutshell, the aftermath of changing history may not always be catastrophic, as mainstream science or various works of science fiction would like to have you believe.