You will notice that the reported bias is always in the direction of AGW. Convenient.
Study: Climate Models Have Been Estimating Rainfall Incorrectly This Whole Time
Most global climate models are underestimating increased rainfall caused by global warming, according to a study released Monday. NASA and four universities compared climate data from 1995 to 2005 to 23 climate model simulations for the same period. More than 70 percent of the climate models underestimated the amount of rain compared to the real world observations.