New data method: Consistent weather station map

I had a new idea for how to look at the big data set made available by Berkeley Earth Surface Temperature. While I now understand the effects of La Niña and El Niño are not worldwide, they do make a difference over a huge amount of the earth's surface so I will continue to consider eras that start and end with a strong La Niña years (or conversely with a strong El Niño years) to be time periods that are worth comparing.

I took the data set and wrote a C program that is interested only in the weather stations worldwide that reported a temperature for every season from 1955 to 2010, both of which are strong La Niña years.  The earliest La Niña to La Niña era is 1955 to 1975, while the most recent spans from 1999 to 2010.  Complete data for 2011 and 2012 is dribbling in, but neither is measured as strong La Niña or strong El Niño, so these are the time periods I use to avoid cherry picking the data, which will often mean the data is not completely up to date.

Tomorrow, I will start showing the results for these consistent weather stations, looking at the difference of the averages of the early and late eras. Splitting the data into the two hemispheres, the northern hemisphere is much better covered than the south, completely unsurprising given the differences in both land mass and population. There are many ways to look at a data set this big and as the week progresses we will go from the simplest ideas to the more complex.