From what you say, they underestimated by 35%. That seems like quite a conservative underestimate.
But guess what. My second link, the NASA one, shows the global increase of temperature between 2001 and 2011 to be 0.03°C. The IPCC estimate was not that conservative, was it? Should I say it was aggressive by a factor of 6?
Nope, I'm not saying that. What I'm saying (and what IPCC is saying) is that generally their predictions appear to be in line with the outcome, and not to be very conservative.
Are we looking at the same graph? Because the graph clearly shows that yearly variation of ~0.2°C is quite normal, and picking any two years separated by 10 years is basically asking for random noise.
When IPCC said global temperature would increase "between about 0.15°C and 0.3°C" in 15 years, they didn't mean "between 1990 and 2005, every successive year will be between 0.01°C and 0.02°C warmer than the previous year." Nor did they mean the year 1990 and 2005 will be "average" years whose temperatures would be smack in the middle of the surrounding time period. To think otherwise shows a fundamental misunderstanding.
Climate scientists are not lawyers. They usually write for people with some scientific training, who can and are willing to follow their arguments for what they are.