Guest Post by Willis Eschenbach
Those who know me are aware that I’m a tropical boy, a hopeless addict of warm blue seas and coconut-laden islands with white sand beaches. Here’s where I used to live and work, Liapari Island in the Solomon Islands.
That is how I like my water to behave, soft, warm, and inviting. But when the ice jumps out of my tropical-type adult beverage and starts running around the countryside covering everything in white and floating in giant chunks all over the ocean, well, I call that “water behaving badly”.
And as you might imagine, other than brief visits I tend to avoid places where water behaves badly.
However, thinking about such icy climes when I’m someplace warm, that’s a more pleasant matter. So I got to considering ice, in particular, sea ice. And as is my wont, when I consider something I go get the longest dataset that I can find. In this case, that was the HadCRUT ice and sea surface temperature dataset. It claims to go back to 1870 … but that doesn’t mean that it’s good back to 1870. Figure 1 shows why.
(As an aside, Figure 1 also shows the importance of starting by running the old Mark I Eyeball over your data before subjecting it to any mathematical gymnastics … but I digress.)
Notice the very regular signal in the early days of both the northern and southern hemisphere data, and as a result in the global data. This is obviously just a perfectly regular repeating signal added to the later actual observations. We can get a better idea of when the real observations start (and stop) by removing the regular repeating seasonal signal from our dataset. Figure 2 below is the same as Figure 1, but with the regular repeating average seasonal variation removed.
The regular signal in the earlier parts of the record is an artifact. It is an interference pattern resulting from the removal of the seasonal signal. Only the latter part of the datasets contain valid observations.
In Figure 2 above we can see that Arctic measurements (northern hemisphere, blue above) are only good since about 1960. Note the odd lack of data (with missing data replaced by a regular signal) from about 1940 to 1952.
Antarctic ice area (southern hemisphere, red above) actual measurements are more recent. The Antarctic record is only good since 1973. As a result, we can only look at global data since 1973. However, that’s approaching a half-century, so it is still of interest. Here’s the global ice area since 1973, the period where we have actual observations. It’s worth noting that since 1979 we have full satellite observations of ice areas.
Now, I was surprised by Figure 3. Surprise is the very best part of science to me. I love the first sight of the graphics, turning what before was just a bunch of numbers into a record of the past.
There were a couple of surprises in Figure 3. First, from 1980 through 2004, a quarter-century during which there was general global warming, there was no trend at all in global ice area. None. Well, to be accurate, the trend 1980 through 2004 is -0.0000000000000001% per decade … and as you imagine, not statistically significant.
After 2005 the global ice area went down, but by 2010 it had recovered. From there to 2015, it was above average. And since 2015 global ice area has dropped precipitously but then recovered back to average. Finally, there is no statistically significant trend in the full 1973 – 2019 dataset.
So … lots of things of interest in Figure 3. However, I gotta say, I’m not seeing the evil hand of steadily increasing atmospheric CO2 in that record. Nor am I seeing any “anthropogenic fingerprint”. Perhaps most importantly, am I unable to detect any sign of any “climate emergency” in that record.
The final surprise was the recent several-year deep drop and then recovery of the ice area. I figured it must be from what alarmists have termed the “Arctic death spiral”, the widely trumpeted decrease in Arctic sea ice. So I added the separate Arctic and the Antarctic records to Figure 3 above. Figure 4 below shows those records.
Curiously, the amount of ice at the two poles is just about the same, at ~2% of the globe. But that makes it hard to compare the Arctic and Antarctic ice. So in Figure 4 below, I’ve offset the northern hemisphere (blue line) by 1% for clarity. You’ll need to add 1% to the northern hemisphere ice areas to get the actual values. Figure 4 shows the globe as well as the two halves of the planet separately. Note that in this graphic they are all to the same scale.
And for my final surprise, it turns out that the recent variations in global ice area are largely the result of variations in the Antarctic ice area, and not in the Arctic ice area that we spend so many electrons discussing …
So what I found out regarding the global ice areas was that I didn’t know all that much about global ice areas … and speaking of which, just what the heck did cause the drop and subsequent recovery in Antarctic sea ice area from 2015 to the present?
Here on the north coast of California, it’s the leading edge of autumn. We had our first rain this week, which left the forest full of the damp dark green smell of life, decay, and rebirth. And when I just looked outside, the rain had come again. What a joy it is to investigate the mysteries of this endless universe, even the vagaries of water behaving badly!
Best to everyone,
via Watts Up With That?
September 30, 2019 at 12:18PM