Snow, snow, snow

News article on how there's snow in 49 out of the 50 states - Hawaii being the only exception.

While a common remark to such news is often a sarcastic "damn global warming!" (I've jokingly said it myself), it's important to realize there's an important difference between weather and climate.  Weather is the day-to-day stuff and sometimes it's hotter than normal and sometimes it's colder than normal.  What's "normal"? 

I can go to a National Weather Service (NWS) website and get weather data for Poughkeepsie, NY (the closest NWS station to where I live).  Today's high temperature was 31 F.  The normal high temperature for this date was 37 F so it was colder than normal today (Saturday, February 13).  Where did this "normal" value come from.  It came from taking the high temperatures for February 13 from 1971 to 2000, adding them together, and dividing by 30 years.  That's how climate is defined - a 30 year average.  We currently use 1971-2000 but on February 13, 2011, the "normal" temperature will be defined as the 30-year average from 1981-2010 (it will switch over on January 1, 2011).

In other words, a bitter cold winter someplace with lots more than normal snowfall doesn't mean global warming isn't true.  One storm or even one winter does not equate with longer term climate change.  If I look at the NWS monthly data report for January 2010, we see that the average monthly temperature was 26.1 F which was 1.6 F warmer than normal. So far February is running a bit colder than normal but the month is only half over.