Was the Arctic Ice Cap ‘Adjusted’? -Still more proof of bogus climate claims

April 6, 2010 19:49

Actually, the rate of growth is statistically insignificant, meaning that a statistician would say that it is neither growing nor shrinking; it just bobs up and down randomly.

By Randall Hoven at American thinker

There is an entity called the National Snow and Ice Data Center. If you go to its website, you can find data and plots of sea ice extent. In particular, you can find the size of the Arctic ice cap, or what the NSIDC calls Northern Hemisphere sea ice. The graph shown on April 2, 2010 is reproduced below.

The data points in this chart reflect the extent of northern hemisphere sea ice in March of each year. The chart indicates that the arctic ice cap is melting — at a rate of 2.6% per decade (about 0.41 million square kilometers). At that rate, the polar ice cap would be gone in 385 years.
Such data have a lot of folks dismissing the CRUgate shenanigans as not all that relevant. Who cares about temperature data when you have the Arctic ice cap staring you in the face? For example, Katie Couric said, “A picture is worth a thousand e-mails, and pictures of the polar ice caps show a 20% decrease since 1979.”
First off, the above graph shows only an 8% decrease over the last 31 years, not a 20% decrease. So Katie would seem to have exaggerated.
But things get really interesting if you look at NSIDC’s raw data, which come from the National Ocean and Atmospheric Administration (NOAA). You will notice that the above chart is of sea ice “extent.” The data actually come in two versions: “extent” and “area,” which are not quite the same.  Here is how the NSIDC explains it.
Important Note: The "extent" column includes the area near the pole not
imaged by the sensor. It is assumed to be entirely ice covered with at least
15% concentration. However, the "area" column excludes the area not imaged
by the sensor. This area is 1.19 million square kilometers for SMMR (from
the beginning of the series through June 1987) and 0.31 million square
kilometers for SSM/I (from July 1987 to present). Therefore, there is a
discontinuity in the "area" data values in this file at the June/July 1987 boundary.
My reading of those “important” words is that the only thing really measured by satellites was “area.” Yet the plot also shows “extent,” something more than was measured. And the difference is something they “assumed.” (If you have a better explanation of that “Important Note,” please enlighten me.)
What were the differences? From the above words from the NSIDC, you would think that the differences would be constant offsets (1.19 million sq km from 1979 through June of 1987, and 0.31 million since). But the actual differences in the data file were not constant at all; they varied between 1.93 and 3.42 million sq km.
Why is the area of an assumed region included in the NSIDC’s graph? More importantly, why does that assumed, non-measured area vary from year to year and month to month in no apparent pattern?
The NSIDC does not provide a plot of the one thing that is measured: area. But I do, below, all based on the raw data provided at the NSIDC’s website.

Using the raw data from the NSIDC, I was able to reproduce its results for “extent.” My calculations using the raw data showed a decline of 2.6% per decade, just as the NSIDC said. So far, so good (or bad, depending on your point of view).
However, the “area” is a different story. Just by eyeball, no trend is apparent. In fact, calculations say that the ice is growing 0.3% per decade!


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