Distribution of temperature changes, U.S. vs. Worldwide

I published this map of weather station in the U.S. that reported consistently from Winter of 1955 to Fall of 2010. The color of the dots represent the difference in the era averages of 1999 to 2010 minus the average from 1955 to 1975. The darkest dots show severe warming, the hollow red dots show warming of less than a degree Celsius and the blue dots show stations that cooled.

Red dots outnumber blue dots, but by how much?

Here are the numbers put on a bar chart. The bar chart looks to be somewhat normally distributed and the average is in the moderate warming range. The severe warming stations slightly outnumber the stations that are cooling.

The worldwide differences still show the average to be in the moderate range, but there are more stations showing severe warming and less showing cooling trends.

In a set of numbers like this, two questions should be asked.

1. Are we measuring something important or not?
2. Could the differences we see just be random chance or is there an underlying reason?

If the measurement is important and it's not just random variation, it could mean that something the United States has been doing for the last half century or so might help slow down the warming trend seen in so many places.