Blast (of cold) from the past

I met my first climate denier at the end of my first semester sophomore year.  During finals week, my roommates and I ran back to our dorm from the dining hall during a relatively typical (at the time) December morning in the upper Midwest.  With a couple of inches of snow on the ground, and temperatures hovering in the single digits, one of my roommates (from Texas no less!), shouted, "Global warming, my ass!"

This December, for the first time in what feels like twenty years, the temperatures have dropped into the single digits with snow and wind chills below zero.  This bout of cold weather, coupled with a recent decrease in the rate of increase of mean temperatures, has given ammunition to those who have the most to lose economically from a clean energy future.  When faced with circumstances like this, we need to remember one important fact:

Climate is not weather.

The day-to-day atmospheric events that affect the temperature and moisture content of the air depend on the climate of a region, but those parameters can vary greatly on a micro-scale (spatially or temporally).  A month or two of seasonally cold weather in one part of the world does not necessarily mean that the climate has shifted one way or another.  Long-term trends of weather define the climate of a region, and the aggregate temperature and moisture conditions across the globe define the global climate.  If this nostalgic December leads to an equally cold remainder of the winter, a seasonable spring, and a summer of limited ninety degree days, then this repeats for ten years, we can say that our climate has returned to what we knew as normal.  Until then, we can lament (or as an avid skier, enjoy) this turn of events, but can draw no conclusions that would cause us to question accepted climate science.

Just two years ago, the weather pattern for the year included a tripling of the average number of ninety degree days, and almost a full year without snow accumulation in the city.  The year before, we had a twenty inch snow event.  Weather changes from year to year, and the level of these swings should give us more pause than the conditions in any one season.  Climate change encompasses the consistency and severity of weather events as well as the temperature.  Assuming that one cold month means the end of climate change makes as much sense as assuming that climate change means we can sell our heavy coats.  Doing so further risks our preparedness, and if predictions continue to come true, we have seen that we need all the preparedness we can get.