WSET.com - ABC13The New Normal by Matt Ferguson

In each weathercast you see on ABC 13 News the current normal high and low temperatures for Lynchburg are shown. While you can think of it as what you would normally expect for that particular day of the year, it's actually an average from 30 years of data. As of July 1, 2011, we are now using a NEW 30 year average from 1981 to 2011, instead of the averages previously used from 1971 to 2001. This is not only the case for temperatures, but also includes rainfall, snowfall, humidity, wind and pressure as well.

Whether you believe in Global Warming or not, it is a fact that the earth's climate has been constantly changing through history. With those ups and downs (in precipitation and temperatures), that is going to affect the average weather for a particular city. The last set of normals came from a period when the US was cooler. Many of you may remember the 1970s being a time of snowier winters. From 2001 to 2010 has been a much warmer period of time for the US. Because of this Global Warming has made headlines often from its advocates. Therefore, when you take out the cool measurements from the 1970s and add the warmer ones from the 2000s, you've got normals that will be warmer than the normals we've used in years past.

Below are several maps from NOAA showing how the normals have changed to a new warmer normal for virtually the entire US.

While I believe the earth's climate has changed with time and will continue to change in the future there are other factors to consider as well. Keep in mind many cities across the country get their official temperature readings from the city's airport. Most airports are in the same place as they were in the 1970s, however the city itself in many areas has grown closer to the airport. So keep in mind the heat island effect. Where the pavement from roads and parking lots, as well as buildings give off heat all night, keeping low temperatures from falling to cooler levels that would possibly happen 10 miles away in more of a countryside location. While the heat island effect is factoring into our new normals, satellite imagery that measures earth's temperatures are not. Since the 1970s satellite data has shown ups and downs in the world wide temperature objectively. It is very interesting to see these highs and lows in 11 year cycles. Currently we are in a warm period, and in years to come it will be fascinating to see if the cycle continues and it becomes cooler once again.

In the coming months don't be surprised to see warmer normal temperatures. As a few years ago, a normal January afternoon high of 49 now may be 50!