BearsWickedBrew - Orfy has spoken.
Hydrometers are calibrated a certain temp, ambient temp / altitude is perhaps a difference of .002 at the most, if your vision and attention to detail is that great, you need to become a commercial brewmaster.
As to your original question.
If you want to up the OG - ABV, you can always just add more DME / LME / Honey / Sugar to the boil.
Each of these ingredients will change your final product unless you adjust, IE DME / LME will need some additional hops to offset the sweetness, honey will make the beer lighter and smoother and extend the brewtime if you use more than two pounds or so.
Sugar, I just do not like adding it to a brew, exceptions for me is making a Chimay or something that requires cracked sugar, etc.
May I recommend some online recipe calculators, they are great to play with, pick your style, build your brew, then all you need is to think about the final taste:
TastyBrew.com | Recipe Calculation
The Beer Recipator 2.2
If these don't meet your needs, then you may want to look at beersmith, Promash, etc.
Hope this helps.