
December 2015 – the warmest month since 1880 (NOAA report) - jrslv
https://www.ncdc.noaa.gov/sotc/global/201513
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nanis
There are, of course, several problems with these kinds of "warmest
evvvaaahhh!!!!" analyses.

First, records in the GHCN date back much further than 1880. Second, the
selection of the records into the GHCN database follows no established
statistically valid process. Historically, humans measured temperature where
they went, not at a random selection of locations on the earth's surface. More
recently, the number of locations at which we have measurements has been
shrinking rapidly.

You can compare statistics from two random samples at different points in
time. You can also compare a series of observations at the same or similar
locations over time. Finally, if you know some econometrics, and you can do
interesting things with panel data while modeling the selection process.

You can't do any of those things with the GHCN.

So, while you can easily say "the average of recorded temperatures is showing
a trend this way or that way," given the fact that what you have is nothing
more than a convenience sample, you cannot say anything about the temperatures
that were not recorded.

If you want to see where humans have recorded temperatures according to the
GHCN, you can take a look at a couple of animations I put together:
[https://www.youtube.com/watch?v=58mDaK9bH5o](https://www.youtube.com/watch?v=58mDaK9bH5o)
and
[https://www.youtube.com/watch?v=gNMgqnUEMGM](https://www.youtube.com/watch?v=gNMgqnUEMGM)

It is not hard for anyone with modest skills to verify this stuff. See
[https://www.nu42.com/2015/11/ghcn-climate-
files.html](https://www.nu42.com/2015/11/ghcn-climate-files.html)

This chart shows the number of observations in the GHCN by year:
[https://www.nu42.com/2015/11/ghcn-obs.png](https://www.nu42.com/2015/11/ghcn-
obs.png)

Finally, here are the sources of 21st century temperature data:

    
    
        Country                             %
        ----------------------------------- -----
        United States of America            45%
        Russian Federation (Asian Sector)    4%
        China                                3%
        Australia                            3%
        Japan                                3%
        Argentina                            2%
        Canada                               2%
        Turkey                               2%
        Algeria                              2%
        India                                1%

