Sea Ice – Because I Promised
Posted by Jeff Id on April 30, 2012
This post is in fairness to the sea ice doom mongers. Some have written that sea ice is the Achilles heel of the non-alarmist. The implication is that the melting is unequivocal and absolutely destructive to the skeptic argument. I’m not an idiot, so why keep posting on sea ice?
Because my opinion is that sea ice isn’t melting from global atmospheric warming – at least not in a major way. My Mrs. Cleo impersonation, which is no better than Klimatologists, is that we will see a little sea ice egg-on-the-face data in the next 5 years. Still, the data is the data, and I did promise to perform the same cutoff for the Antarctic as I had done for the Arctic and provide some kind of global single year ice trend.
Unfortunately, the Antarctic has a strong circumpolar current which catches sea ice in a strange pattern that is not suited to latitudinal cutoffs. Big deal, I knew about this result before I said I would do it.
The result is explained below. I cut off all data below -65 degrees Latitude South and above 72 degrees Latitude North.
From those plots I excluded all Antarctic sea ice North of -65 latitude, an admittedly pro AGW choice as the vast majority of the ice in the Antarctic vanishes even south of that line.
My calculation for the southern hemisphere single year ice trend is:
Southern hemisphere (Antarctic) Sea ice North of -65 Latitiude doesn’t exhibit a significant positive trend. It is close though and there are some oddities in the data. Every year this sea ice returns to basically zero. The wiggles are hard to spot but this zero value causes an artificially increased variance in the standard anomaly calculation. It also alters the very basic lag-1 value such that “significance” here is not very accurate.
We have eliminated a LOT of the Antarctic sea ice by this calculation. This is the absolute area value for the Antarctic sea ice North of -65
You can see that sea ice really does return to zero North of -65 degrees. More importantly for us is that the average sea ice level for the above plot is 2.89 million Km^2 whereas the total Antarctic is 9 million Kilometers^2. Yet the average minimum Antarctic sea ice is only 1.8 Km^2 so 80% of the annually melting Antarctic ice is being ignored. We need a non-circular mask.
All that means is that this next plot is pretty worthless. It shows the trend in sea ice for the globe comprised of a reasonable, yet imperfect, Arctic mask and a piss-poor Antarctic mask. Still, I promised I would do it.
We have a statistically significant trend in sea ice for underrepresented Antarctic data and Arctic data on a global scale. I suppose that it is now up to me to provide a more interesting version of this post. After all, if SWAG (Super Warming Activists Guild) is happy with an incomplete presentation here, that is probably something we need to rectify.