Ice Cores

Ice cores are used to demonstrate on charts what the global mean temperature was thousands of years ago.  I read this wikipedia article on Ice Core and it was talking about how the cores only show local temperature.  Put this great bit of knowledge together with today's explanation of cooler temperatures being a side-effect of global warming because an increase in global temperatures will cause a greater disparity of local temperatures, up or down.  So, how can we trust the temperatures in just a few locations to show us to any degree of accuracy of what the temperature really is?

Midieval Warm Period

Are we warmer now than in the Midieval Warm Period?  Or, is it colder?  I've found a chart from the IPCC that shows it was warmer then than now:

So, if that has changed, what data changed, or was it massaged because it was incorrect?  Help me out here!  I don't know what to believe.  Is global warming getting out of control, or are we slowly returning to a warmer temperature that we are supposed to be at?

How can I get my hands on the raw data for all this?