Megan,
given the best information we have now, there is more uncertainty at the high end of climate sensitivity than at the low end.
Does this conclusion from Nordhaus (2012) address your point?
we conclude that no loaded gun of strong tail dominance has been uncovered to date.
http://onlinelibrary.wiley.com/doi/10.1111/j.1467-9779.2011.01544.x/full