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Wednesday, May 14, 2008

A Fresk Look At NCDC Absolute - Data Source Notes

Update: I was advised yesterday, May 16th, that JunkScience corrected the errors described in the following.

In the text of the first part of this series, I wrote that I originally downloaded the .csv files from JunkScience. I have not noted that I had subsequently downloaded the NCDC monthly anomaly data found here:

Then followed the NCDC directions for creating the absolute data:

There are no differences in the global land and sea and the global sea data if you use the JunkScience spreadsheets or create your own, but there are insignificant differences in the January and February mean land temperatures. This is apparently caused by an NCDC change in base monthly mean temperature data for January and February (two of those twelve monthly numbers). Since these differences in the monthly mean land temperatures effect the data for each year, and since they are so small in comparison to the annual variations in mean land temperatures, there is no problem using the JunkScience spreadsheets for simple blog evaluations such as these. The graph resolution can’t pick up the differences. However, if you’re going to process the data using the multitude of available filters, you would be wise to follow the NCDC directions and create your own absolute global temperature data.

That way you won’t have to go back and update your work halfway through your analysis or, worse, after you’ve created all the graphs and uploaded them!

This morning I notified JunkScience of their need to update the Land data. I was later notified they will post a note on the webpage and correct the problem shortly.

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