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Receding glacier causes Canadian river to vanish in four days

theguardian.com

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Re: Receding glacier causes Canadian river to vanish in four days

#71

Post by drt1245 »

archgoon wrote: post #64
Almaviva wrote: post #30

Earlier quoted context omitted.

The 0.5% quote is fine. It's turning it into a 99.5% that is not fine. It's essentially like saying that a pair of dice that rolled a 12 has a 97% chance of being loaded, because there's only a 1 in 36 chance of rolling that high.

Let's think about this. Let's assume that when a river gets redirected, a scientist goes and investigates it (which seems reasonable), and is asked what is the chance that it happened by natural causes, or is due to global warming. Based on the analysis that @acover shared with us, we can see that out of a thousand such dispatches, 995 will be due to global warming and 5 will be due to natural variability. So it seem…

>Let's assume that when a river gets redirected, a scientist goes and investigates it

This is a faulty assumption and is what leads to the wrong conclusion. The probability of 0.5% is for a randomly selected river. That is, if you went and examined 200 randomly selected rivers, 1 of them (on average) would be redirected due to natural variability.

That does not imply that the remaining 199 were redirected due to global warming. It does not even imply that the remaining 199 were redirected at all!

What is needed is the percentage of rivers that have undergone this redirection. Here's a simplified example: If it's ~0.5%, you conclude it's just natural variation. If it's >0.5%, you conclude that something (possibly global warming) is increasing the number of rivers that are being redirected. If it's <0.5%, you conclude that something is decreasing the number of rivers that are being redirected.

Re: Receding glacier causes Canadian river to vanish in four days

#72

Post by burntrelish1273 »

OliverJones wrote: post #4

There's another possibility of the event this author calls "river piracy." The Mississippi river is chronically at risk of being grabbed by the Atchafalaya River. John McPhee wrote about this in 1987. http://www.newyorker.com/magazine/1987/02/23/atchafalaya

For a second, I was thinking sand piracy.

https://www.washingtonpost.com/world/asia_pacific/indias-ill...

Re: Receding glacier causes Canadian river to vanish in four days

#73

Post by Mz »

One problem with the way this is framed:

Rivers have historically meandered. They didn't have a set path. The modern expectation that rivers have a set path is one we tend to try to actively enforce.

Elsewhere in comments here, someone noted that the Salton Sea is similar. But if you read Salt Dreams, Native Americans had oral history suggesting that there had been a lake there previously. Geological records agree with the oral history.

Re: Receding glacier causes Canadian river to vanish in four days

#74

Post by burntrelish1273 »

Almaviva wrote: post #2

"The calculations put chance of the piracy having occured due to natural variability at 0.5%. “So it’s 99.5% that it occurred due to warming over the industrial era,” said Best." We need to train children in school to understand what statistical confidence means, so that we stop saying wrong things like this.

Definitely.

Another good idea is to show the difference between reality and data can be overwhelmingly significant.

Videos demonstrating this with examples:

- "The Bayesian Trap" https://youtu.be/R13BD8qKeTg

- "Is Most Research Wrong?" https://youtu.be/42QuXLucH3Q&

Re: Receding glacier causes Canadian river to vanish in four days

#75

Post by archgoon »

drt1245 wrote: post #71
archgoon wrote: post #64

Earlier quoted context omitted.

Let's think about this. Let's assume that when a river gets redirected, a scientist goes and investigates it (which seems reasonable), and is asked what is the chance that it happened by natural causes, or is due to global warming. Based on the analysis that @acover shared with us, we can see that out of a thousand such dispatches, 995 will be due to global warming and 5 will be due to natural variability. So it seem…

>Let's assume that when a river gets redirected, a scientist goes and investigates it This is a faulty assumption and is what leads to the wrong conclusion. The probability of 0.5% is for a randomly selected river. That is, if you went and examined 200 randomly selected rivers, 1 of them (on average) would be redirected due to natural variability. That does not imply that the remaining 199 were redirected due to glob…

> The probability of 0.5% is for a randomly selected river

Sorry, what is the probability .5% for exactly? The probability a river is redirected under global warming conditions? I didn't think that's what they computed. If it is, then my bad. :) I thought they had computed given that the river was redirected, what is the likelihood it happened due to global warming. Ah well, like I said, the details are the hard part. :)

Re: Receding glacier causes Canadian river to vanish in four days

#76

Post by acover »

drt1245 wrote: post #71
archgoon wrote: post #64

Earlier quoted context omitted.

Let's think about this. Let's assume that when a river gets redirected, a scientist goes and investigates it (which seems reasonable), and is asked what is the chance that it happened by natural causes, or is due to global warming. Based on the analysis that @acover shared with us, we can see that out of a thousand such dispatches, 995 will be due to global warming and 5 will be due to natural variability. So it seem…

>Let's assume that when a river gets redirected, a scientist goes and investigates it This is a faulty assumption and is what leads to the wrong conclusion. The probability of 0.5% is for a randomly selected river. That is, if you went and examined 200 randomly selected rivers, 1 of them (on average) would be redirected due to natural variability. That does not imply that the remaining 199 were redirected due to glob…

From the paper:

"shows our estimate that there is only a 0.5% chance that the observed retreat of Kaskawulsh Glacier happened in the absence of a climate trend"

The 0.5% has nothing to do with the river. It is their confidence that the retreat of the glacier could occur in the absence of a climate trend based on their model.

Re: Receding glacier causes Canadian river to vanish in four days

#77

Post by gnaritas »

kensai wrote: post #49
inetknght wrote: post #9

I'm thinking you're commenting on the wrong article ;) Did you mean -> https://news.ycombinator.com/item?id=14131759

Guys, I seriously do not know wtf happened. I never opened this "Receding glacier" thread. I was commenting on the Intel thread and my comment somehow ended up here. I got aware of it because of all these negative points which came quite unexpected. Could it have been a glitch in the database?

HN has no database, it's all just a bunch of files on the file system.

Re: Receding glacier causes Canadian river to vanish in four days

#78

Post by spodek »

titojankowski wrote: post #35

Sweet, so what should we build to change this? Giant carbon-sucking machines, cube-sats pointed at glaciers? (planet labs is doing cool stuff in this space, including a project to count every tree on Earth every day). Solutions welcome!

At a low level:

- Have fewer children

- Burn fewer fossil fuels (less driving, flying, heating, cooling, more wearing sweaters at home in winter, etc)

- Eat less meat

- Develop technologies to create energy without fossil fuels

At a higher level

- Stop associating consumption and material accumulation with happiness

- Stop targeting growth (population, GDP, etc) as solution to so many problems

- Take personal responsibility for what you do. Stop saying if others don't change my change won't make a difference. You are responsible for what you do even if others don't change.

At the top level:

- Change you beliefs and goals so that instead of asking others, you find what you can do and do it. There is overwhelming amounts of information for what you can do already on the web. If you want to act, act.

Re: Receding glacier causes Canadian river to vanish in four days

#79

Post by archgoon »

acover wrote: post #76
drt1245 wrote: post #71

Earlier quoted context omitted.

>Let's assume that when a river gets redirected, a scientist goes and investigates it This is a faulty assumption and is what leads to the wrong conclusion. The probability of 0.5% is for a randomly selected river. That is, if you went and examined 200 randomly selected rivers, 1 of them (on average) would be redirected due to natural variability. That does not imply that the remaining 199 were redirected due to glob…

From the paper: "shows our estimate that there is only a 0.5% chance that the observed retreat of Kaskawulsh Glacier happened in the absence of a climate trend" The 0.5% has nothing to do with the river. It is their confidence that the retreat of the glacier could occur in the absence of a climate trend based on their model.

Can you clarify why it is incorrect to reverse that into the statement "We estimate that there is a 99.5 percent chance that the observed retreat did not happen in the absence of a climate trend."? I confess to a fair amount of confusion at this point :) I'm sure there is something subtle (or perhaps obvious, and my brain is failing) that I'm missing.

What is the properly worded complement?

Re: Receding glacier causes Canadian river to vanish in four days

#80

Post by [deleted] »

acover wrote: post #76
drt1245 wrote: post #71

Earlier quoted context omitted.

>Let's assume that when a river gets redirected, a scientist goes and investigates it This is a faulty assumption and is what leads to the wrong conclusion. The probability of 0.5% is for a randomly selected river. That is, if you went and examined 200 randomly selected rivers, 1 of them (on average) would be redirected due to natural variability. That does not imply that the remaining 199 were redirected due to glob…

From the paper: "shows our estimate that there is only a 0.5% chance that the observed retreat of Kaskawulsh Glacier happened in the absence of a climate trend" The 0.5% has nothing to do with the river. It is their confidence that the retreat of the glacier could occur in the absence of a climate trend based on their model.

[deleted]
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