As even with the Muller analysis, temperature spikes like we're experiencing are relatively rare.
What I gather from Richard Muller's assessment of Michael Mann's temperature spike graph (the hockey stick) is that the math used to chart that graph was flawed.
What I gather from my understanding of paleoclimatology methods (interpreting tree ring and ice core data) is that they aren't 100% accurate. We know that tree ring data is unreliable because it didn't respond to 20th Century warming of northern latitudes. We know that ice core data isn't totally reliable because we get different data from Antarctica than we do from Greenland. Also, we have no ice core data from most of the planet's surface. That's a lot of missing data. We can't say definitively that there wasn't a 30 year stretch of warming during the Eemian period (the last interglacial period) comparable or even more extreme than the years 1979 to 2009. To do so would be an argument over less than a degree Celsius and there's too many blind spots to go back 120,000 years and attempt to do that.