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Death by hockey sticks

dothemath.ucsd.edu

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Re: Death by hockey sticks

#41

Post by WoodenChair »

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:

"We show that—contrary to the prevailing view that forest area has declined globally5—tree cover has increased by 2.24 million km2 (+7.1% relative to the 1982 level). This overall net gain is the result of a net loss in the tropics being outweighed by a net gain in the extratropics. Global bare ground cover has decreased by 1.16 million km2 (−3.1%), most notably in agricultural regions in Asia. Of all land changes, 60% are associated with direct human activities and 40% with indirect drivers such as climate change." [0]

0: https://www.nature.com/articles/s41586-018-0411-9

Re: Death by hockey sticks

#42

Post by mupra »

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:…

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.

Re: Death by hockey sticks

#43

Post by WoodenChair »

mupra wrote: post #42
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:…

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).

Re: Death by hockey sticks

#44

Post by sdenton4 »

mupra wrote: post #42
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:…

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 getting our collective shit together and slowing down? Or will it be a massive die-off after we've destroyed the ecosystems we depend on for things like air to breathe and water to grow our crops?

Re: Death by hockey sticks

#45

Post by x-complexity »

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...

> 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.

Re: Death by hockey sticks

#46

Post by Barrin92 »

Old and fairly trivial insight is that most hockey-stick graphs end up being S-curves and that's already in sight for most of the ones given here. Population is on its way to a plateau, so is energy consumption in the rich world, and so on. Economic growth due to poor nations caching up will still keep going for a while but it's not that unlikely that we'll eventually end up in a fairly static situation at least for a time, which wasn't uncommon in human history.

runaway scenarios without anything reigning them in are very rare or otherwise we wouldn't be here talking about them because we'd all have drowned in Tribbles already.

There's a lot of psychology in these imagined scenarios and relatively little long-run empirical observation because complex systems tend to have a significant amount of constraints and regulatory mechanisms that kick in either voluntarily or involuntarily to impose some limits on growth. They tend to be more cyclical in nature rather than tending towards unlimited or even linear growth.

Re: Death by hockey sticks

#47

Post by cmgxyz »

dafty4 wrote: post #28

Don’t plot the amount of wild mammalian biomass, plot the amount of totally mammalian biomass. Doubt you’ll see a downward hockey stick in that case. What makes a wild mammal more special than a domestic one?

Nothing, but that doesn't mean they deserve extinction. It'll be a poorer Earth if it's all housecats and no tigers.

What makes us more special than other animals? Also nothing, in my view.

Re: Death by hockey sticks

#48

Post by narrator »

The biggest problem with our sustainability is we literally piss massive amounts of nitrogen into the ocean and replace it with the Haber-Bosch process. You had farmers in Asia farm the same land for 40 centuries all powered by "night soil" or humanure or the various other euphemism for it.

Re: Death by hockey sticks

#49

Post by emmelaich »

HomeDeLaPot wrote: post #9

I hope this is overly pessimistic and under-analyzed. For example, the human population hockey stick graph doesn't show the dramatic drop in birth rates experienced by developed countries. We are on track to reach a global population maximum. And is the author too zealous in drawing hockey stick curves over any 2 or 3 data points? Is deforestation still accelerating? Any chance extinctions will decelerate?

Yep, I've seen a UN projection that has us flattening out at 10billion.

Re: Death by hockey sticks

#50

Post by emmelaich »

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.

Phytoplankton are under appreciated as a carbon sink. In comparison, forests can sometimes be a carbon source!

> Phytoplankton biomass in the world's oceans amounts to only ∽1-2% of the total global plant carbon, yet these organisms fix between 30 and 50 billion metric tons of carbon annually, which is about 40% of the total

https://pubmed.ncbi.nlm.nih.gov/24311124/

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