8 ms·

I found it a bit clickbaity. The title is correct to the letter but not really to the spirit, because down at the bottom there is: > Temperatures are known to

I found it a bit clickbaity. The title is correct to the letter but not really to the spirit, because down at the bottom there is: > Temperatures are known to vary wildly over Antarctica, and massive swings are common. Contrasting with this warm spell over eastern Antarctica, the South Pole observed just observed its coldest April to September period on record last year, with an average temperature of minus-78 degrees (minus-61 Celsius). But to be sure "The heat dome was exceptionally intense, five standard deviations above normal" is nuts. We should rename Antarctica to something like "Crazy continent".

ianai 5y ago
Uhh last I checked 5 standard deviations was the definition of a statistically significant difference. To me it sounds like a realization that climate changes will have drastic and possibly chaotic effects.
- WinterMount223 5y ago
  Do you know the temperature probability distribution in Antartica? Not all distributions are normal and not all even have a standard deviation.
  - ianai 5y ago
    Standard deviation is defined by the distribution under question.
  - deleted 5y ago
    [deleted]
  - FabHK 5y ago
    The probability that an observation is beyond 5 standard deviations is < 1/25 = 4%, according to Chebyshev's inequality, provided the variance of the distribution is finite (which, as you say, is not guaranteed, eg. for Cauchy distributed random variables). https://en.wikipedia.org/wiki/Chebyshev's_inequality https://en.wikipedia.org/wiki/Chebyshev's_inequality https://en.wikipedia.org/wiki/Cauchy_distribution https://en.wikipedia.org/wiki/Cauchy_distribution
    - WinterMount223 5y ago
      If the observed variable is “the mean temperature in a given day”, 4% can be expected to occur relatively frequently. Anyway until we know the probability distribution, and my intuition says that it’s definitely not Normal for wide periods of time, we can’t say if it’s significant or not.
      - ianai 5y ago
        You’re the only one introducing the normal distribution here.
        nobodyandproud 5y ago
        When discussing standard deviations, what meaning is there for non-normal distribution? https://stats.stackexchange.com/questions/108578/what-does-standard-deviation-tell-us-in-non-normal-distribution#197545 https://stats.stackexchange.com/questions/108578/what-does-s...
      - lanstin 5y ago
        Five standard deviations is not four percent, it is in the 1 in 3 Million range.
        FabHK 5y ago
        Yes, for a normal, which is known to have extremely thin tails (decaying with a squared exponential!). Chebyshev's bound holds for any possible distribution (with finite variance).
    - zmgsabst 5y ago
      4% would imply that we should expect about two weeks of such weather every year, in total. Which would make this article somewhat clickbait — nothing more than “wowza, July 15th is another hot one in California!” Since it’s currently summer, in the Southern Hemisphere.
      - 5y ago
teawrecks 5y ago
I think you're hearing "massive swings" and jumping to the conclusion that 5 std dev is somehow normal-ish behavior for the region. It's not. At all. By definition.
- mattcwilson 5y ago
  That’s absolutely right. But as the article itself says, we don’t know if this is the start of some trend or if this is a never previously observed fluke. Climate change is about regression to a mean that is itself higher than the previous mean. But with or without human contribution, weather events are still going to regress to a mean.
  - nwallin 5y ago
    > But as the article itself says, we don’t know if this is the start of some trend or if this is a never previously observed fluke. ...That's not how statistics works. A 2 sigma deviation can be a never previously observed fluke. A 5 sigma variation ... that means that the model is wrong. Observing a 5 sigma variation means that you need to stop, and consider why your model is incorrect. > Climate change is about regression to a mean that is itself higher than the previous mean. That's what we've been assuming, but this result upends that assumption. We talk about a new mean that's 5F higher than the old mean. But an event that's 70F higher than the current mean is also 65F above the the 'new' mean. And that throws out the possibility what we're talking about is a new mean that's higher than the old mean with the same standard deviation. The brave new world we're walking into doesn't just have a higher average temperature, it also has a significantly higher standard deviation. And this is potentially catastrophic. If Antarctica is, on average, 5F warmer, but is not prone to significant deviations, then Antarctica stays frozen. This is our old model; maybe the new extremes are a little bit more extreme, but Antarctica is still so cold and the rare high temperature events are mild enough that it's still gonna be super cold, and all the ice that's held up in the Antarctic ice sheets stay there. But if we have wild swings like this one, then our old models are quite simply wrong. We now need to start to consider models where Antarctica melts, and now we need to consider a 190 foot increase in sea level over the next century. AFAIK that means that a majority of Earth's population will be displaced. NYC, London, Tokyo, Florida, Rio, all gone.
yodon 5y ago
When you start calling five sigma events "click-baity" you may find others asking legitimate questions about your ability to assess what is significant. Encountering a headline that tries to get people to read the article is a roughly zero-sigma event. That's the purpose of a headline, and has been for about 150 years. Retailers also sell things for more than they paid for them and supply chains are hard. If you can understand what a five sigma event is, you can understand these things as well.
- tlokas 5y ago
  I must agree on the "click-baity" title. If it wasn't for the article being posted on HN, I would never have clicked on the title, as it includes something like "Scientists are flabbergasted".

ianai 5y ago

Uhh last I checked 5 standard deviations was the definition of a statistically significant difference. To me it sounds like a realization that climate changes will have drastic and possibly chaotic effects.

WinterMount223 5y ago
Do you know the temperature probability distribution in Antartica? Not all distributions are normal and not all even have a standard deviation.
- ianai 5y ago
  Standard deviation is defined by the distribution under question.
- deleted 5y ago
  [deleted]
- FabHK 5y ago
  The probability that an observation is beyond 5 standard deviations is < 1/25 = 4%, according to Chebyshev's inequality, provided the variance of the distribution is finite (which, as you say, is not guaranteed, eg. for Cauchy distributed random variables). https://en.wikipedia.org/wiki/Chebyshev's_inequality https://en.wikipedia.org/wiki/Chebyshev's_inequality https://en.wikipedia.org/wiki/Cauchy_distribution https://en.wikipedia.org/wiki/Cauchy_distribution
  - WinterMount223 5y ago
    If the observed variable is “the mean temperature in a given day”, 4% can be expected to occur relatively frequently. Anyway until we know the probability distribution, and my intuition says that it’s definitely not Normal for wide periods of time, we can’t say if it’s significant or not.
    - ianai 5y ago
      You’re the only one introducing the normal distribution here.
      - nobodyandproud 5y ago
        When discussing standard deviations, what meaning is there for non-normal distribution? https://stats.stackexchange.com/questions/108578/what-does-standard-deviation-tell-us-in-non-normal-distribution#197545 https://stats.stackexchange.com/questions/108578/what-does-s...
    - lanstin 5y ago
      Five standard deviations is not four percent, it is in the 1 in 3 Million range.
      - FabHK 5y ago
        Yes, for a normal, which is known to have extremely thin tails (decaying with a squared exponential!). Chebyshev's bound holds for any possible distribution (with finite variance).
  - zmgsabst 5y ago
    4% would imply that we should expect about two weeks of such weather every year, in total. Which would make this article somewhat clickbait — nothing more than “wowza, July 15th is another hot one in California!” Since it’s currently summer, in the Southern Hemisphere.
    - 5y ago

teawrecks 5y ago

I think you're hearing "massive swings" and jumping to the conclusion that 5 std dev is somehow normal-ish behavior for the region. It's not. At all. By definition.

mattcwilson 5y ago
That’s absolutely right. But as the article itself says, we don’t know if this is the start of some trend or if this is a never previously observed fluke. Climate change is about regression to a mean that is itself higher than the previous mean. But with or without human contribution, weather events are still going to regress to a mean.
- nwallin 5y ago
  > But as the article itself says, we don’t know if this is the start of some trend or if this is a never previously observed fluke. ...That's not how statistics works. A 2 sigma deviation can be a never previously observed fluke. A 5 sigma variation ... that means that the model is wrong. Observing a 5 sigma variation means that you need to stop, and consider why your model is incorrect. > Climate change is about regression to a mean that is itself higher than the previous mean. That's what we've been assuming, but this result upends that assumption. We talk about a new mean that's 5F higher than the old mean. But an event that's 70F higher than the current mean is also 65F above the the 'new' mean. And that throws out the possibility what we're talking about is a new mean that's higher than the old mean with the same standard deviation. The brave new world we're walking into doesn't just have a higher average temperature, it also has a significantly higher standard deviation. And this is potentially catastrophic. If Antarctica is, on average, 5F warmer, but is not prone to significant deviations, then Antarctica stays frozen. This is our old model; maybe the new extremes are a little bit more extreme, but Antarctica is still so cold and the rare high temperature events are mild enough that it's still gonna be super cold, and all the ice that's held up in the Antarctic ice sheets stay there. But if we have wild swings like this one, then our old models are quite simply wrong. We now need to start to consider models where Antarctica melts, and now we need to consider a 190 foot increase in sea level over the next century. AFAIK that means that a majority of Earth's population will be displaced. NYC, London, Tokyo, Florida, Rio, all gone.

yodon 5y ago

When you start calling five sigma events "click-baity" you may find others asking legitimate questions about your ability to assess what is significant. Encountering a headline that tries to get people to read the article is a roughly zero-sigma event. That's the purpose of a headline, and has been for about 150 years. Retailers also sell things for more than they paid for them and supply chains are hard. If you can understand what a five sigma event is, you can understand these things as well.

tlokas 5y ago
I must agree on the "click-baity" title. If it wasn't for the article being posted on HN, I would never have clicked on the title, as it includes something like "Scientists are flabbergasted".