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Color me a little skeptical - but I remember a big noise about how the drought that california was intensified by climate change.. I mean I guess its possible t

by Aloha 9y ago

Color me a little skeptical - but I remember a big noise about how the drought that california was intensified by climate change.. I mean I guess its possible that the drought and increased rainfall are caused by the same thing. https://www.nytimes.com/2015/08/21/science/climate-change-intensifies-california-drought-scientists-say.html https://www.nytimes.com/2015/08/21/science/climate-change-in... When I look at the weather patterns California has had over the last 5-10 years, I see something that fits within the historical norms for the state.

kbutler 9y ago
The model projections provide enough variability to allow for virtually any result, so the results most likely to get press are emphasized. They have no predictive power.
- KirinDave 9y ago
  I don't really understand why you'd say this. They absolutely have predictive power. This is like saying that because there are error margins that we can't take the mean and extract meaningful data from it. If that were the case, nearly all classic statistics would be powerless. Spoiler alert: it is not.
  - kbutler 9y ago
    It's because the model results project more snow and less snow. More rain and less rain. More severe weather and less severe weather. The example cited by the GP illustrates this - 2 years ago during the drought, climate models predicted continuing severe droughts for California. Now, they predict continuing increased precipitation. The results haven't actually changed, just different subsets are being reported. The global results are better than the regional results, but tend to run hotter than observations, suggesting they don't yet account for the full range of natural variability. Statistics don't help you predict a coin flip (actually I think tails is ever-so-slightly more likely) Edit: the point is not that a particular model can't make predictions. Some models will actually be correct. We just don't know which regional models are correct, and because of the range of results, they cannot all be correct. Therefore, as a whole, the regional models have no predictive power. The stock market is a good example. Lots of people make lots of money betting on their models, but lots of people lose lots of money when their model stops working. There is also a general rising trend underlying the whole system.
    - KirinDave 9y ago
      The model that predicts your lifespan predicts people with more and less life, with varying probability. It actually does have predictive power for your lifespan, but it does so in a probabilistic way. The idea that a distribution doesn't have power because it is a distribution is a bizarre opinion to encounter in a community that prides itself on education, computer science, business acumen, machine learning, and informed decision making.
      - jackmott 9y ago
        it is pretty similar to the latest meme on climate change which is that imperfect models are not suitable for making policy decisions. so I guess we have perfect models for economics and social issues and geopolitical issues now.....so that we can make any policy decision.
    - jackmott 9y ago
      the model predicts more heat, not less. the model predicts less ice, not more. period. so, you've got that.
    - cjbprime 9y ago
      > (actually I think tails is ever-so-slightly more likely) Why do you say this? For which coin?
      - kbutler 9y ago
        Heads tends to be heavier (not sure if this is a general rule). Discussion of US penny: http://www.smithsonianmag.com/science-nature/gamblers-take-note-the-odds-in-a-coin-flip-arent-quite-5050-145465423/ http://www.smithsonianmag.com/science-nature/gamblers-take-n... But with a coin flip, the initial side up is a bigger bias.
        KirinDave 9y ago
        … Its precisely statistics that can help us identify these trends in coin flips and if there actually is observable effects to these weights.
schizoidboy 9y ago
I'm no expert, but I did a bit of research into this since I live in California, and here's data that supports the parent's assertion: https://radicaloptimism.org/wiki/In_The_News#California_Drought https://radicaloptimism.org/wiki/In_The_News#California_Drou... It seems to me that the patterns fit within the historical norms for over 100 years.
- Retric 9y ago
  Sort of, the 5 year running average is well below the norm, which is an important metric as Dam's can't hold enough water to really average over ~50 years. Further, because the lows are bound by 0, the annual average is rather deceptive.
aphextron 9y ago
>I mean I guess its possible that the drought and increased rainfall are caused by the same thing. From the abstract: "This uncertainty is related to several factors, including relatively large internal climate variability, model shortcomings, and because CA lies within a transition zone, where mid-latitude regions are expected to become wetter and subtropical regions drier." So yes, it looks like CA is in for both. Increased aridity in the south, with more extreme precipitation hitting the north.
ricw 9y ago
The climate predictions are exactly that: longer droughts and more rainfall when it does happen. Source: life partner who studies climate science...
- rdtsc 9y ago
  In a few words what is the general model to explain it? Is it because the atmosphere becomes a better heat sink so it can store more energy? And then consequently release more of it?
  - deleted 9y ago
    [deleted]
  - js8 9y ago
    I am no expert, but I think the general intuition is that more energy means more violent fluctuations due to dynamical nature of weather. Just like water that is being more heated has stronger turbulences in it. More specifically, extreme events in the moderate latitudes are explained by slowdown and amplification of Rosby waves: https://en.wikipedia.org/wiki/Rossby_wave https://en.wikipedia.org/wiki/Rossby_wave

by Aloha 9y ago

kbutler 9y ago

The model projections provide enough variability to allow for virtually any result, so the results most likely to get press are emphasized. They have no predictive power.

KirinDave 9y ago
I don't really understand why you'd say this. They absolutely have predictive power. This is like saying that because there are error margins that we can't take the mean and extract meaningful data from it. If that were the case, nearly all classic statistics would be powerless. Spoiler alert: it is not.
- kbutler 9y ago
  It's because the model results project more snow and less snow. More rain and less rain. More severe weather and less severe weather. The example cited by the GP illustrates this - 2 years ago during the drought, climate models predicted continuing severe droughts for California. Now, they predict continuing increased precipitation. The results haven't actually changed, just different subsets are being reported. The global results are better than the regional results, but tend to run hotter than observations, suggesting they don't yet account for the full range of natural variability. Statistics don't help you predict a coin flip (actually I think tails is ever-so-slightly more likely) Edit: the point is not that a particular model can't make predictions. Some models will actually be correct. We just don't know which regional models are correct, and because of the range of results, they cannot all be correct. Therefore, as a whole, the regional models have no predictive power. The stock market is a good example. Lots of people make lots of money betting on their models, but lots of people lose lots of money when their model stops working. There is also a general rising trend underlying the whole system.
  - KirinDave 9y ago
    The model that predicts your lifespan predicts people with more and less life, with varying probability. It actually does have predictive power for your lifespan, but it does so in a probabilistic way. The idea that a distribution doesn't have power because it is a distribution is a bizarre opinion to encounter in a community that prides itself on education, computer science, business acumen, machine learning, and informed decision making.
    - jackmott 9y ago
      it is pretty similar to the latest meme on climate change which is that imperfect models are not suitable for making policy decisions. so I guess we have perfect models for economics and social issues and geopolitical issues now.....so that we can make any policy decision.
  - jackmott 9y ago
    the model predicts more heat, not less. the model predicts less ice, not more. period. so, you've got that.
  - cjbprime 9y ago
    > (actually I think tails is ever-so-slightly more likely) Why do you say this? For which coin?
    - kbutler 9y ago
      Heads tends to be heavier (not sure if this is a general rule). Discussion of US penny: http://www.smithsonianmag.com/science-nature/gamblers-take-note-the-odds-in-a-coin-flip-arent-quite-5050-145465423/ http://www.smithsonianmag.com/science-nature/gamblers-take-n... But with a coin flip, the initial side up is a bigger bias.
      - KirinDave 9y ago
        … Its precisely statistics that can help us identify these trends in coin flips and if there actually is observable effects to these weights.

schizoidboy 9y ago

I'm no expert, but I did a bit of research into this since I live in California, and here's data that supports the parent's assertion: https://radicaloptimism.org/wiki/In_The_News#California_Drought https://radicaloptimism.org/wiki/In_The_News#California_Drou... It seems to me that the patterns fit within the historical norms for over 100 years.

Retric 9y ago
Sort of, the 5 year running average is well below the norm, which is an important metric as Dam's can't hold enough water to really average over ~50 years. Further, because the lows are bound by 0, the annual average is rather deceptive.

aphextron 9y ago

>I mean I guess its possible that the drought and increased rainfall are caused by the same thing. From the abstract: "This uncertainty is related to several factors, including relatively large internal climate variability, model shortcomings, and because CA lies within a transition zone, where mid-latitude regions are expected to become wetter and subtropical regions drier." So yes, it looks like CA is in for both. Increased aridity in the south, with more extreme precipitation hitting the north.

ricw 9y ago

The climate predictions are exactly that: longer droughts and more rainfall when it does happen. Source: life partner who studies climate science...

rdtsc 9y ago
In a few words what is the general model to explain it? Is it because the atmosphere becomes a better heat sink so it can store more energy? And then consequently release more of it?
- deleted 9y ago
  [deleted]
- js8 9y ago
  I am no expert, but I think the general intuition is that more energy means more violent fluctuations due to dynamical nature of weather. Just like water that is being more heated has stronger turbulences in it. More specifically, extreme events in the moderate latitudes are explained by slowdown and amplification of Rosby waves: https://en.wikipedia.org/wiki/Rossby_wave https://en.wikipedia.org/wiki/Rossby_wave