What are some possible causes that might explain why the global temperature has remained relatively constant in the last decade?
Not my field but I have a couple of thoughts:


According to your link, the blue line represents the change in the trend and the red bars are the temperatures. These have not remained that stable, it is the bar that gives that illusion:


A much more important point are the grey bars extending above and below each year's value. This is the range of uncertainty, the actual values could be anywhere within the range of those bars. Notice how the uncertainty decreases the closer you get to the current date. 


I think a lot of the stability you observe is probably due to the line hiding the detail and the far lower precision of the older measurements.