Handy image shows how climate deniers manipulate data
This image from Skeptical Science is a great illustration of how data can be manipulated to serve your purpose. It shows how skeptics point to small declines in temperature by comparing warm years with cold ones seven to 10 years later — but if you trace the trend over 40 years, you see an obvious warming pattern. Temperatures may cycle over the decades, but each cycle gets a little warmer.
Going Down the Up Escalator, Part 1, Skeptical Science.