In November 2011 Dana N. at Skeptical Science produced this striking animated graph called ‘The Escalator.’ The graph clearly demonstrates how critics cherry-pick short periods of time to convince themselves that ‘warming is over.’ [See "Skeptical cherry-picking, brilliantly exposed!"]
‘The Escalator’ went viral, and has also become a target for skeptics, who try to poke holes in it by questioning the actual data from which the graph is constructed, rather than concentrating on its learning point.
But challenging the data misses the whole point. It does not matter what the data represents because the point of the graph is to expose a simple fact: Whenever there are many random variations (noise) in a graph, it is possible to find short periods when an observer can be deceived about the actual pitch (steepness) of the slope. The overall trend becomes apparent only when we zoom out to look at a longer time period.
This is why to extract a meaningful trend for global temperatures, which are influenced by so many variables, scientists recommend looking at a minimum period of about 30 years.
It’s a bit like climbing up a rocky mountain in a fog. Have we reached the top, or is it just a false crest? Only when the path starts to climb downhill for a while can we be reasonably confident that we have passed the peak. And even then, not until we get back to the starting altitude can we say for certain that our climb is over.
For anyone who needs more evidence that global temperatures are still rising, check out NASA’s site: http://climate.nasa.gov/keyIndicators/