One of the things that drives me berzerk about the global warming debate is the use of anecdotal evidence. Global warming supporters will cite Hurricane Katrina or a hot summer as evidence that global warming exists. Global warming detractors will cite a cold winter as evidence that it’s false.

In science, this is known as “cherry picking” — taking only the data that support your view instead of analyzing all the data. Global warming is a slow process, one that’s much more subtle than the natural year to year variations in global temperature. It doesn’t just show up in July all of the sudden.

Imagine that you were listening to the radio. Sometimes the music is loud, sometimes the music is soft. But the volume is being turned up slowly — so slowly you can hardly notice. But after a while, you have a headache.

A graph of the planet’s temperature will look very spikey as we have cold years and warm years — literally noise. But slowly, the spikes are moving upward.

Whatever you think of global warming, the plural of anecdote is not data (hat tip, Robert). A hurricane or a heat wave do not prove global warming any more than a cold snap disproves it. It’s the slow steady accumulation of planet-wide data that reveals the process.