The earth is always in a constant state of temperature change. This has been true since long before humans were here, and will continue long after we are gone. The question of the last couple generations has been; Are Humans causing an above average temperature shift?
XKCD, one of my favourite online comics, has done an excellent graphic detailing the comparative shift of temperature in the planet. This graph clearly outlines how the planet has gone through minor temperature fluctuations in years past, but is accelerating exponentially now.
I would like to note that I have NOT verified any of the data that XKCD has used to make their graph, so I can not confirm it’s accuracy. Given the scientific depth that XKCD usually uses to make their comics, I tend to lean on the side of believing their interpretation of the data. Of course, I invite you to verify the data yourself.Direct Link