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Death by hockey sticks

dothemath.ucsd.edu

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Re: Death by hockey sticks

#71

Post by Archelaos »

sdenton4 wrote: post #44
mupra wrote: post #42

Earlier quoted context omitted.

A hockey stick is the initial part of an S-curve. A point to consider is that all complex systems are functions of multiple variables and more often than not, non-linear. A complete view of the past and the present is not a guarantee of the future. At best, it can be a guide for having cautious behavior.

(It's a day ending in y, so here I go again...) It depends on the sign of the exponent. Negative exponential growth, as we see in wild animal populations, is not guaranteed to turn into an S-curve. As the passenger pigeon would attest, were any of them left. Meanwhile, to consider a positive exponent case, there's a real question of what will actually cause the bend in the curve of human population. Will it be gettin…

> It depends on the sign of the exponent. Negative exponential growth, as we see in wild animal populations, is not guaranteed to turn into an S-curve. As the passenger pigeon would attest, were any of them left.

Sigmoid functions are defined over real input values (not integers). If you were to model the decline in (integer) numbers of passenger pigeons with reals, you would get a sigmoid function were the number at the end approximates, but never reaches zero.

Re: Death by hockey sticks

#73

Post by quickthrower2 »

thematrixturtle wrote: post #66
strken wrote: post #52

Earlier quoted context omitted.

Australian aboriginal land management probably kept the number of trees down, compared to what they would have been prior to human settlement. Dry season burns were used to clear away brush and deforest areas.

The vast majority of Australia has been inhospitable desert since before the Aboriginals showed up. Trees can only grown on a comparatively narrow stretch of temperate or tropical, mostly coastal land.

Australia's desert would be helping to keep the % a bit lower, globally.

Re: Death by hockey sticks

#74

Post by ZeroGravitas »

EGreg wrote: post #35
sacrosancty wrote: post #13

Earlier quoted context omitted.

Hockey sticks usually end up being S-shaped curves. The author is just doom-screaming because we're currently in the rapid change phases of lots of them but hasn't shown on any of the graphs the point where disaster will occur. What's the critical rate of extinctions that would end global economic growth before most of the world has western quality of life? He has no clue! So his worries are just emotional and based…

I'm not sure how S-shaped curves help when it comes to the collapse of all ecosystems is concerned... are we supposed to innovate our way out of rapidly dwindling biodiversity on the planet? insects and pollinators birds and large game animals forests and rainforests kelp forests dying coral reefs dying overfishing plastic pollution greenhouse gas pollution acidification of oceans 1/3 of all arable land underwent des…

Because the people profitting from the direct causes of many of these issues, fossil fuels and industrial meat, started a culture war with the people who were concerned about them.

Anyone who popped their head up to address any of these problems was attacked and undermined by very well funded adversaries.

Any crank that argued against them even being a problem got promoted.

We struggled to get them to stop poisoning humans with lead and cigarettes and poverty for the same reasons.

Re: Death by hockey sticks

#75

Post by quickthrower2 »

EGreg wrote: post #31

Finally! A website that highlights the root cause ... Human population growth. This is the input to all the other stuff. The past few generations thinks they're the most sophisticated and intelligent, but they're living on an ecological credit card. And the bill is going to come due. Just like any bill after a spending spree, this is going to be a doozy. Probably extinction level...

So not the super extravagant, energy-intensive lifestyles of said humans?

Re: Death by hockey sticks

#76

Post by wildmanxx »

m_dupont wrote: post #62
WoodenChair wrote: post #41

You can't make hockey sticks out of just a few data points, as this author does in several of the charts. For example, the deforestation chart is based on a few data points from a UN study (where Our World in Data that the author links to cites as its source). But tree coverage has actually increased over the past 30 years according to some studies by NASA and elsewhere. For example, one 2018 paper from Nature says:…

Yeah the worst thing is that with the extinction rate, he states that he implicitly sets the background extinction rate to 0 in the year 1000. This is going to bias his 3-point curve fitting even moreso. The background extinction rate in the absence of humans is probably much higher than 0. New species are also continuously emerging while others are going extinct, so that the total number remains steady.

You are kinda arguing against your point.

Around the year 1000, it's a reasonable guess to assume that emergence of new species and species extinction were roughly in balance, so net extinction rate was indeed around 0.

Today, it's well-established that this net extinction rate is as horrible as is described. A few new species emerging here and there are not enough to compensate for the mess that we are causing on the extinction front, by orders of magnitude.

Re: Death by hockey sticks

#77

Post by quickthrower2 »

agileAlligator wrote: post #60
x-complexity wrote: post #45

Earlier quoted context omitted.

> Finally! A website that highlights the root cause ... > Human population growth. Please don't go down this path: Every time someone does so, it always leads to eugenics in some form or another.

We practice eugenics with almost every lifeform we have domesticated but refuse to do so with ourselves, just coz some guy with a funny mustache got it confused with muh white masterrace.

Wow that skidded off the beaten track quickly.

Population controls !== eugenics

Dominating animals is part of human nature / DNA. Not sure what we do about it. Stop eating meat probably becomes ahead of stop breading poodles.

Re: Death by hockey sticks

#78

Post by thaumasiotes »

WoodenChair wrote: post #43
mupra wrote: post #42

Earlier quoted context omitted.

A hockey stick is the initial part of an S-curve. A point to consider is that all complex systems are functions of multiple variables and more often than not, non-linear. A complete view of the past and the present is not a guarantee of the future. At best, it can be a guide for having cautious behavior.

You don't even have the beginnings of any meaningful predictive curve with just a few data points. It's just selective function fitting if there's not a rich data set. For example, you can draw many curves through 2 data points, but you can also draw a straight line. The Our World in Data "Primary vs. planted forest" data that he cites for the "Old Growth Forest Cover" chart has just 2 data points (1990 and 2019).

> You don't even have the beginnings of any meaningful predictive curve with just a few data points. It's just selective function fitting if there's not a rich data set.

Having a rich data set doesn't help. https://twitter.com/SonerCagaptay/status/1389387850551005192

Re: Death by hockey sticks

#79

Post by derbOac »

throwabob123 wrote: post #36
soared wrote: post #20

I don’t know much about forests but it seems incorrect that at any point in time 55% of land mass was covered by forests.

> I don’t know much about forests The past was amazing. One example: Trees predated organisms that broke them down, so at some point there were just piles of trees, many tens or even a few hundreds of feet, on land, and that's why some trees are theorized to grow so tall so fast. Just on the face of it though, you're a layperson, but you find soil, coal, peat, lots of biotic mass almost everywhere, what do you think…

Near here is a state park with an interpretive natural history center. They have a photo from of a nearby intersection that always completely blows my mind.

The photo is from the very early 20th century, and the area at that time was original old growth forest. Huge trees everywhere in the photo, the road is just really a trail. It's a completely different landscape, and the only thing similar I've seen in person is maybe the redwood national park forests.

What's wild to me is the area is currently very rural. So there's forest in the area today, around that intersection. But it's still so different. The road now is so much bigger and the quality of the forest is so much different now — it just seems like succession forest by comparison.

The area was logged after the photo, which was the point of displaying it. But what's crazy is it's been 100 years and it still looks nowhere near the same.

Re: Death by hockey sticks

#80

Post by cornel_io »

WoodenChair wrote: post #41

You can't make hockey sticks out of just a few data points, as this author does in several of the charts. For example, the deforestation chart is based on a few data points from a UN study (where Our World in Data that the author links to cites as its source). But tree coverage has actually increased over the past 30 years according to some studies by NASA and elsewhere. For example, one 2018 paper from Nature says:…

Yep - "hurr durr I fit a two parameter exponential to three data points OMG guys we should panic now" is just about the weakest argument that has ever been made about any of this stuff.

At the very least, many of the things he's showing would be theoretically expected to follow logistic curves of some form, not pure exponentials.

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