At the Foresight Institute, J. Storrs Hall had some interesting graphs made from NOAA ice core data (Alley, R.B. 2000. The Younger Dryas cold interval as viewed from central Greenland. Quaternary Science Reviews 19:213-226.)
Note the unique rise from 1840 to about 1880. This is a terribly sudden rise. Now just as Mann and Briffa look at their bristlecone and tree ring data sets with flat temperature histories in much of this same period and then append the land surface instrumental measurement data to the late 20th Century as enhanced by the urban heat island effect to create a similar hockey stick set of temperature data, we examine this data in the same mindset. Well, clearly the early industrial age, though limited to Britain mostly at that time, with the U.S. and Germany as minor players, was very effective in altering the world's climate! Shame on those Brits! It's really their fault. They should pay us punitive taxes! Indeed, the Brits owe everyone in the whole world.
We should note that there has been a further temperature rise in fits and starts after 1900 of about another 0.5 C. Dare we look further back in history as seen by Greenland ice? Awwww......sure, why not. We are intrepid explorers here!