Tuesday, May 20, 2008

A fun Causality mistake...

Lew Rockwell writes
A recent study claimed that labor unions increase the productivity of firms. How did the researchers discern this? They found that unionized companies tend to be larger with more overall output than non-unionized companies
Hard to believe the relationship is causal:

In fact, what we have here is a simple mix up of cause and effect. Bigger companies tend to be more likely to attract a kind of unpreventable unionization than smaller ones. The unions target them, with federal aid. It is no more or less complicated than that. It is for the same reason that developed economies have larger welfare states. The parasites prefer bigger hosts, that's all. We would be making a big mistake to assume that the welfare state causes the developed economy. That would be as much a fallacy as to believe that wearing $2,000 suits causes people to become rich.

Sunday, May 04, 2008

Sea Ice Continued

A friend of mine sent me a pointer to an interesting online article written to clarify some of the technical controversies endemic to climate change debate. I learned the following:
  • yes; it is acknowledged that some scientists have argued that sea ice in the Antarctic has increased until 2002.
  • the increase is possibly due to changing wind patterns due to the hole in the Ozone.
  • less warm air in the interior causes more ice to accumulate in the winter.
  • in contrast, on the exterior, sea ice is shrinking overall.
  • By 2006, the overall total is lower.
First, let me emphasize that sea ice on the exterior floats (e.g. the Wilkins Ice Shelf) so overall sea levels are inelastic with respect to changes in exterior ice. Second, the Ozone story is post-hoc interpretation; it is not science. Soft scientific analysis is only impressive when it makes successful and risky predictions. How did climate scientists do on that score? In 2006, it was reported that the total amount of ice was shriking at an alarming rate:

THE first survey of gravity changes caused by the Antarctic ice sheet has confirmed that it is shrinking at an alarming rate.
I turns out that the scientists looked at 2002-2005 data and yes, over that time that the total sea ice (mass; as opposed to area) in the Antarctic was indeed shrinking. Woops! If they had actually bothered to consider past data they would have seen the reality for what it is: changes that are well within the limits of natural variation. In fact, 2005 was an unusual large drop in area (as it can easily be seen from my previous graph) and that should have been noticed. A good analysis would have predicted some regression back to the overall mean in area (all the more so if the Ozone hole theory were taken into account). Three more years later and we are right back on the general increasing trend. Yet, our "climate change" guru has this to say

A more recent study based on satellite measurements of gravity over the entire continent suggests that while the ice sheets in the interior of Antarctica are growing thicker, even more ice is being lost from the peripheries.
Alas; the study was not current by the time this was written. It was already contradicted by current data and now with the 2008 numbers it seems that the point is wholly wrong.

Thursday, May 01, 2008

Southern Hemisphere Sea Ice

On the news page of the National Snow and Ice Data Center (NSIDC) there is an article about the possible collapse of the Wilkins Ice Shelf
Antarctic Ice Shelf Disintegration Underscores a Warming World Satellite imagery reveals that a 13,680 square kilometer (5,282 square mile) ice shelf has begun to collapse in Antarctica.
The article is all very interesting, but I wanted more information since I am not sure why we should care particularly about one ice shelf that is comparitively small. I was surprised to discover that this March has seen the largest increase in Southern Hemisphere sea ice since we started measuring: So which is it? Is global warming causing BOTH the melting of the Wilkins AND the increase in total Southern Hemisphere Ice? How on earth can the NSIDC justify such a misleading headline on their news page? A better headline would be "Antarctic Sea Ice increase undermines Warming World"