[Pog0]

Assuming you play equally well multitabling as you do single tabling, varience is the same in both if your measurement of time is hands played rather than hours spent playing. The reason people say that you have lower varience multitabling is because the shorter the session, the larger the varience.

if you play 100k hands, although your varience is high over each individual session, if you count the 100k hand session as a whole, your return will be relatively close to your winrate (random guess would be True winrate +/- 1 BB/100, while over 10k hands you would have your True winrate +/- 3 BB/100).

The only way to decrease varience (and it doesn't really decrease varience but rather deem it less significant) is to play more hands. Multitabling you will make varience less significant in less time.

Best to think in terms of hands rather than time.