How do we measure a "global mean temperature"? I was a bit curious about that and Steven Bloom, a commenter at Climate Science, provided a link to the NASA site that has a database and neat maps to show all of that global warming.
The map below shows the really cold spell in North America and arctic Russia, but the vast areas of heat in the polar north and central Asia. There are some gray areas but the planet is pretty well measured. Right? Well, maybe not. This happens to be a map with a 1,200 km (500+ mile) "resolution". Kind of like watching a TV with 1" pixels. You kind of, maybe, could make out the picture.
Note the scale which is "variance from seasonal normal." Minus 8 degrees to plus 8 degrees. Most of the heating is in the northern hemisphere.
Now let's take a look at the data from the database plotted out to a finer resolution of 250 km (100+ miles).
Whoa! Where are all of the measurements? What happened to Canada and Africa and Australia and those overheating polar regions? Suddenly most of the planet looks gray!
And the scale is different, too. The minus 8 degrees to plus 8 degrees suddenly becomes minus 21 degrees to plus 10 degrees.
Okay, lets presume no one is fudging the data, but this is what happens when you build some algorithms to "fill in the blanks".
You can read my additional climate at Climate Science.