(CNN)This week, a trillion-ton hunk of ice broke off Antarctica.
You probably know that. It was all over the Internet.
Among the details that have been repeated ad nauseam: The iceberg is nearly the size of Delaware, which prompted some fun musing on Twitter about where exactly Delaware is and how anyone is supposed to approximate the square footage of that US state. The ice, which has been named A68, represents more than 12% of the Larsen C ice shelf, a sliver on the Antarctic Peninsula. And most important: None of this has anything to do with man-made climate change.
The problem: That last detail -- the climate one -- is misleading at best.
At worst, it's wrong.
Some scientists think this has a lot to do with global warming.
I spent most of Thursday on the phone with scientists, talking to them about the huge iceberg off Antarctica and what it means. Here are my five takeaways.
http://www.cnn.com/2017/07/14/world/sutter-iceberg-antarctica-climate-change/index.html
[Warning: CNN autoplay video - Ed]
(Score: 5, Insightful) by maxwell demon on Monday July 17 2017, @06:52AM (14 children)
Maybe they should start with a clear definition of what it means to "have anything to do with man-made climate change". Because it's absolutely not clear what this is supposed to mean.
Consider a biased coin that has slightly higher odds to give heads. I toss it and it gives heads. Does this result have anything to do with the coin being biased? On one hand, yes, the coin being biased means it more likely did give heads, so getting heads on that toss was certainly influenced by the coin's bias. On the other hand, no, I could also have gotten heads with an unbiased coin, and I need many tosses to see the difference between the unbiased and the biased coin.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by moondrake on Monday July 17 2017, @08:34AM (5 children)
I came here to post such an example, but could not have formulate it so eloquently as you did.
This is exactly what is going on here, and is why it can be both interpreted as evidence and as coincidence. It is a single data point.
Now the gradual thinning in ice in the area over decades correlated to warmer temperatures (I have no idea if this is true) might be stronger evidence of a link (but is still only a correlation).
In the end, it does not matter. Ice melting is no evidence for climate change, it is simply a consequence of it.
(Score: 0) by Anonymous Coward on Monday July 17 2017, @09:04AM
Another issue is that human contribution is accelerating and magnifying the effect of global warming. Global warming itself is not unexpected and is part of a regular equilibrium our planet had fallen into the past ~million or so years. Granted, we should have long since (in terms of temperature/CO2, not necessarily time) begun to stabilize and enter into the next ice age, but the degree, length, and scale of warming are all very relevant here. Ultimately this just looks like more Clickbait News Network.
(Score: 1) by khallow on Monday July 17 2017, @09:23AM (3 children)
Consequence and evidence is not mutually exclusive. A car wrapped around a tree can be both evidence and consequence of poor driving.
(Score: 2) by moondrake on Monday July 17 2017, @01:57PM
that was sort of exactly my point though. Which is why different people explain this iceberg differently.
(Score: 0) by Anonymous Coward on Monday July 17 2017, @02:06PM (1 child)
Isn't that evidence of insufficient logging?
(Score: 1) by khallow on Tuesday July 18 2017, @01:51AM
(Score: 2) by PiMuNu on Monday July 17 2017, @09:49AM
Good metaphor
(Score: 0) by Anonymous Coward on Monday July 17 2017, @02:56PM (6 children)
I actually never like these examples. They seem to say that flipping a coin is the only way to determine if it is biased. I'd say it is clearly one of the worst ways to try going about that. Instead you should measure the physical properties of the coin, balance it on its edge in a vibration/wind free environment, etc.
Flipping it is what social/medical researchers would do. The latter is what physicists/engineers would do.
(Score: 2) by maxwell demon on Monday July 17 2017, @06:49PM (5 children)
Not instead. In addition. If you measure the physical properties of the coin, you can say that it is not entirely symmetric, but you will not convince those who deny that the asymmetry actually leads to a bias in heads vs. tails. After all, coin tossing is a complex process, and lots of things like air currents in the room influence it, how can you say what this asymmetry really does for the probabilities? Sure, you can make simulations, but then, what about the effects you neglected because your computer is only so powerful?
The Tao of math: The numbers you can count are not the real numbers.
(Score: 0) by Anonymous Coward on Monday July 17 2017, @08:00PM (4 children)
Yes, measure the physical properties of the coin and use these to predict the coin should come up heads x% of the time. Then when you test the coin by flipping it should be close to this value you have predicted (rather than the NHST approach of checking "50% heads").
(Score: 1) by khallow on Tuesday July 18 2017, @02:04AM (3 children)
We ignore here that the NHST does work here without the need for model building of the coin which may be costly and still miss biases of the coin (particularly, if those biases are designed to hide from your measurements of the physical properties of the coin). And what does "test the coin by flipping it should be close to this value you have predicted" mean? NHST in disguised form.
NHST has its place. Here, low cost testing of numerous supposedly unbiased, identical, independent observations is one of its more useful roles.
(Score: 0) by Anonymous Coward on Tuesday July 18 2017, @03:32AM (2 children)
No, it is not the same at all. In my suggested case we are building a physical model of the coin and saying "coin is biased by this much", if the model then predicts the correct amount of biasedness (with "enough" precision and accuracy) we can trust the model that the coin is actually biased.
In the NHST case we assume "coin has exactly zero bias" and test this by just checking the results of flipping the coin. As pointed out by maxwell demon there are many schemes and environmental effects that can result in a bias while the coin is just fine.
The second difference is that once your model is tested repeatedly and shown to work, you no longer "need many tosses to see the difference between the unbiased and the biased coin." In the NHST case you will keep having to collect huge amounts of data each time. There is no cumulative knowledge being gained.
(Score: 1) by khallow on Tuesday July 18 2017, @11:40AM (1 child)
Once again I reiterate my claim that we have NHST here. You describe hypothesis testing, with an implicit comparison to the null hypothesis.
Those schemes and environmental effects will be just as much a problem with your testing of your model's predictions.
(Score: 0) by Anonymous Coward on Tuesday July 18 2017, @02:30PM
NHST is not the same as hypothesis testing, which is not the same as significance testing. What I describe is closest to Fisher's significance testing, there is a huge literature about the mass confusion caused by the mash up of hypothesis testing and significance testing. If you were trained in the last 50 years to do applied stats there is 99% chance you were taught NHST (which is wrong).
The schemes and environmental effects would not be a "problem", they are further parameters to include in the model once discovered. There is no way to do this for the NHST case.