# Why the 13-Month Moving Average on Satellite Data?

Explanation of the Satellite Data Moving Average:

Global area-averaged lower tropospheric temperature anomalies (departures from 30-year calendar monthly means, 1981-2010). The 13-month centered average is meant to give an indication of the lower frequency variations in the data; the choice of 13 months is somewhat arbitrary… an odd number of months allows centered plotting on months with no time lag between the two plotted time series. The inclusion of two of the same calendar months on the ends of the 13-month averaging period causes no issues with interpretation because the seasonal temperature cycle has been removed as has the distinction between calendar months.

While doing some research I stumbled upon an article on Think Progress that appeared to be mocking Dr. Spencer at the UAH regarding his usage of a 13-month moving average.

If you’re wondering why Spencer plots a 13-month running average when 13 months do not actually correspond to anything relevant to homo sapiens, well, you’ll have to ask him. It is slightly easier to do the math. In any case, here is the more meaningful 12-month running average from Sou at HotWhopper:

What is so funny about this, is that the “more meaningful 12-month running average from Sou at HotWhopper” showed almost the exact same increase, both peaking at essentially 0.50 Degree, and very slightly exceeding the previous peak.

Here is the chart Dr. Spencer produced:

Here is the chart “Hot Whopper” produced:

Dr. Spencer’s graph is a “centered” moving average and is why Dr. Spencer uses 13-months instead of 12. A “centered moving average” averages data behind and forward in a time series. The problem is, even numbers don’t work well with centered average. Using a 12-month period, the forward calculation includes June, July, August, September, October, November, and December or 7 months, and back calculation includes January, February, March, April, and May, or 5 months.

Even numbers create asymmetrical moving averages. To make “Hot Whopper’s” moving average a “centered” moving average and symmetrical, he would have had to apply a 2-period moving average to his 12-period moving average. The article made no mention of “Hot Whopper’s” chart being “centered.” To exaggerate the warming “Hot Whopper” stretched the vertical axis and compacted the horizontal axis relative to the UAH graphic.

The other benefit of a centered moving average is that it “hugs” the data better, and better fits the graph. That is why the moving average ends 6.5 months before the end of the data. Had one used the trailing 12-month average the graph would have been shifted to the right, and the moving average would be leading the data. The opposite would have occurred is you had used a forward 12-month average.

Either way, a moving average is simply a method to “smooth” data, and remove seasonality. One could make the case for using both Dr. Spencer’s and Hot Whopper’s, both give essentially the same result and are appropriate. The difference certainly doesn’t justify an article intended to smear one’s character and integrity.

In truth, none of this is funny. The lies of the professional deniers get repeated by the politicians and right-wing media who oppose action — and all that helps slow our response to the greatest preventable threat to our health and well-being. That is a tragedy we must all fight against.

The one thing “Think Progress” didn’t do however was to write a follow-up article now that temperatures are plunging. They were all eager to celebrate the Satellite data reaching a new high due to non-CO2 related El Nino, but are silent now that temperatures are collapsing. Funny how that works in the progressive world.

Sorry deniers, even satellites confirm record global warming
The planet just had its hottest 12 months on record.

One last note, the person writing the Think Progress article claims to have a Ph.D, and writes as if he is trying to entertain children. Additionally, the article is filled with unethical, unjust and unscientific Ad Hominin attacks. “Deniers” was used 10 times in a single short article.

Now here’s the funny part [not funny ha-ha, but that emoji where you are laughing so hard tears are coming out of your eyes and then you realize those aren’t tears of joys, they are just tears].

It is really an eye opener to see just how childish people of the left address this issue.

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