Cold Snap

cold-snapClick to enlarge. It's cold in the winter. Some people think that cold weather disproves global warming. That's because they don't understand the difference between weather and climate.

Weather measures the local environmental conditions, typically on the scale of hours or days. Climate measures the average environmental conditions over larger scales of time, typically on the scale of decades or even centuries. The weather conditions of any single day (or even a month) really don't matter much. And in fact, you would expect to have some days that were significantly hotter or significantly colder than others. That's why we talk about average conditions: so that one freezing day (or two or ten) doesn't distort the big picture.

It may be cold today, but that doesn't change the fact that 2010 tied with 2005 for the warmest year on record.

Comic originally posted: Dec. 5, 2009