I don't know how one could alter the strength of the barbarians' attack level. However, there are two methods that one can alter the science increment ... but both methods benefit and/or hurt *all* the players, not just the human one.
1. Cheat menu: Go under this menu and change the game file into a scenario file. Afterwards, there's an option w/i that menu which allows you to change the science increment. The higher the numerator, the longer it takes to get advances while vice-versa holds true as well.
2. Rules.txt: Enter this file and you can change the science increments under the universals part of the file. WARNING: This method IS NOT recommended by myself (and the programmers) because universals control the fundamental basics of Civilization games. If they're too far out of what the CPU expects to find, the program will react in really bad ways. I know, 'cause I found out the hard way (read: partial re-installation of program).
Resistance is futile. Lower your shields and disable your weapons. You will be assimilated into the Borg Collective.