Let's suppose you have no particular axe to grind and are wondering about what 2011's average temperature will look like. What are some things you would do? First, of course, is try to get some data to work with. I'm choosing the NCDC global land and sea temperatures, annual average. If you prefer some other source, go with that. And if you're interested in something entirely different than this, have a go with that data source. I'll be talking about methods of dealing with data, not anything unique to annual average global mean 2 meter air temperatures.
Next is to do some basic looking around the data. That includes plotting it, finding the maximum, the minimum, the average, and the standard deviation. Since you're thinking about making a prediction of 2011, you also want to take a look at how things change from year to year. What does the plot of year to year change look like? What are the maximum, minimum, average, and standard deviations of change?
Time and Tide: Crash Course Astronomy Episode 8
5 hours ago