OT: Climate Change, Isaac Asimov and the 1975 TV Guide

Asimov did the too-common thing of assuming that feedbacks always cause oscillation. Control theory is real and involves more than qualitative speculation. The "oscillations" are more likely to be caused by external forcings.

We are now in a very pleasent, people-friendly, probably transient warm spell. The average temp of the planet is a lot lower.

It's the small-scale Anthropic Principle: we enjoy a warm, fertile planet because, if it were in its normal cold state, we'd be dead and nobody would be around to appreciate it.

Well, he was a chemist, so what do you expect? ;)

Cheers

Phil Hobbs

There are only a few cases of chemical oscillations. They are extremely rare, so Asimov should have been biased towards gradual equilibrium.

I don't know of any cases of purely thermal heat-driven oscillations.

Steam engines. ;)

But in the absence of mass motion, heat flow is governed by a PDE that's first order in time and has real-valued coefficients, so it doesn't give rise to imaginary exponentials. (Schroedinger is first order in time as well, but has an i in it, so it has no real-exponential solutions.)

Cheers

Phil Hobbs

There is the famous R-C circuit with voltage gain

and it seems to me that there ought to be a thermal equivalent. But we'd still need more stuff to make an oscillator.

There is a thermally-driven u-tube liquid oscillator, but it does involve mass transport.

We've talked about thermoacoustic fridges here not so long ago. They're magic.

Cheers

Phil Hobbs

om:

agic.

Now, *that's* funny!

for the February 22, 1975 issue of the TV Guide and called "The Weather Mac hine". It was reprinted as "The Big Weather Change" in "The Beginning and t he End" a collection of Isaac Asimov essays.

You can get the book here.

warm and cold. Sometimes the Arctic Ocean is open water and then it supplie s water vapor which falls on the surrounding land areas as snow. If there i s then a small drop in general temperature for a prolonged stretch of time not all the snow that falls each winter will melt each summer.

own weight to form glaciers. The glacier ice reflects Sunlight more effici ently than bare ground does and cools the Earth further, so that still less of the snow that falls in the winter is melted, and the glaciers advance s outhward.

reezes over and the supply of water vapor is cut off. Less snow falls, so t hat the summer melting becomes more effective and the glaciers begin to ret reat. The retreat reduces the ice cover, allows the Earth to warm, and acce lerates the retreat further. When it grows warm enough for the ice on Arcti c Ocean to melt, it starts all over."

Nice story. The fact that the Arctic Ocean doesn't have to melt in an inter glacial - and hasn't for most of this one - demonstrates that it's more a f able than a story.

without the human effect.

co2temp800kyrs-large.jpg

g around 450 thousand years ago. The present day is right at the point wher e the North Pole melts and turns on the Arctic Ocean's snow making machine.

Except that it doesn't. The effect that leads to a lot of snow being occasi onally dumped further south than usual is a occasional kink in the jet stre am, rather then any kind of snow-dumping conveyor belt.

the Arctic Ocean's snow making machine is still going to turn on.

Not that it ever did in any previous ice age. That's doesn't seem to be the way the changeover works.

the Arctic Ice Cap returning in 100,000 years, it might return in a million years or it might never return. We end up with stable halo of ice around t he North Pole.

We've injected a lot of CO2 into the atmosphere. It's going to be turned to carbonate rock in due course, which takes tens of thousands of years.

nce! Science! Scary! Scary! Gives us $100 billion/year and we'll save you!" I think it's bullshit. You're not going to stop the North Pole from meltin g and the North Pole melting doesn't prove anything. That's just part of th e natural cycle that's been going on for half a million years.

! We've have nothing to worry about!" No, that's what happens when the Nort h Pole melts and it is going to get worse. What makes all this nonsense wor se is that we knew about it 40 years ago.

Actually, we didn't. Asimov was improvising.

A bit silly, even for John. Modern humans go back to the previous interglac ial.

The Mitochondrial Eve lived between 152 and 234 thousand years ago.

There's a fairly convincing argument that humans evolved language and cultu re in order to be able adapt faster to the alternations between ice and age and interglacials than their predecessors could. They certainly ended up l iving - and thriving - in a lot of very different environments.

Modern industrial society has yet to show itself to be equally flexible. Mo st of it has discovered anthropogenic global warming - John Larkin is an ex ception - but nobody is doing enough to stop it getting worse.

I was a chemist once, and I've certainly ticked off John for making the mis take of claiming that all positive feedbacks drive system to their limits, which is - of course - denying that they cause oscillations, since a "pegge d" system isn't oscillating.

All true. The transient warm spell which we are bringing on by burning a lo t of fossil carbon and dumping a lot of CO2 into the atmosphere is going to be transient, but the geological process of turning all the CO2 into carbo nate rock and burying them is going to take quite bit longer than the avera ge interglacial, and probably longer than the average ice age.

John Larkin is weak on quantitative thinking. His qualitative thinking isn' t too impressive either.

ov for the February 22, 1975 issue of the TV Guide and called "The Weather Machine". It was reprinted as "The Big Weather Change" in "The Beginning an d the End" a collection of Isaac Asimov essays.

ok. You can get the book here.

of warm and cold. Sometimes the Arctic Ocean is open water and then it supp lies water vapor which falls on the surrounding land areas as snow. If ther e is then a small drop in general temperature for a prolonged stretch of ti me not all the snow that falls each winter will melt each summer.

ts own weight to form glaciers. The glacier ice reflects Sunlight more effi ciently than bare ground does and cools the Earth further, so that still le ss of the snow that falls in the winter is melted, and the glaciers advance southward.

freezes over and the supply of water vapor is cut off. Less snow falls, so that the summer melting becomes more effective and the glaciers begin to r etreat. The retreat reduces the ice cover, allows the Earth to warm, and ac celerates the retreat further. When it grows warm enough for the ice on Arc tic Ocean to melt, it starts all over."

le without the human effect.

ting around 450 thousand years ago. The present day is right at the point w here the North Pole melts and turns on the Arctic Ocean's snow making machi ne.

jpg

and the Arctic Ocean's snow making machine is still going to turn on. I thi nk it would just change the period of the triangle wave. Instead of the Arc tic Ice Cap returning in 100,000 years, it might return in a million years or it might never return. We end up with stable halo of ice around the Nort h Pole.

cience! Science! Scary! Scary! Gives us $100 billion/year and we'll save yo u!" I think it's bullshit. You're not going to stop the North Pole from mel ting and the North Pole melting doesn't prove anything. That's just part of the natural cycle that's been going on for half a million years. I also th ink the bozos yelling, "It's colder and snowing more this winter! We've hav e nothing to worry about!" No, that's what happens when the North Pole melt s and it is going to get worse. What makes all this nonsense worse is that we new about it 40 years ago.

The oscillation is spatial, rather than temporal, unless you look at it fro m the point of view of chunk of the fluid that is convecting.

True, the quasi-periodic fires in California's brushlands are not purely thermal (there's a biological growth/deadwood element).

More generally applicable, is the accumulation of instability: any slight fire (human or natural) causes an abnormally high response, if the last fire in the area was many years ago... but not if all the brush burned last year.

That kind of instability gives rise to catastrophes, and is a compelling reason for controlled burns to limit the brush accumulations. In the 1970s, it wasn't known that CO2 accumulation would occur (sinks, like ocean uptake, weren't quantified until later). We're currently seeking ways to limit CO2 accumulation.

Interesting concept that oscillations of the earth's temperature are caused by "external forcings". I believe in the Greek tragedies they called that deus ex machina.

I find it especially amusing that John seems to think mankind won't survive an ice age. I don't know the ice ages killed off so many animals really. Certainly one which is not only warm blooded, but able to use external devices (think fire) to control body temperature has a significant advantage over the tree lemurs.

There are poikilotherms and homeotherms. I wonder what you call organisms that regulate body temperature by burning dinosaurs?

Even funnier is the idea that an engineer analyzing climate makes fun of a noted science writer because he was trained as a chemist. Talk about irony.

What??? Try looking outside your window!!!

Experts? We don't need no steenkin' experts.

(And we should just have newly minted grads designing complex electronic/software systems. Not.)

f a noted

I did pretty well as a graduate student. I did a lot better after I'd learn ed a bit more. There's nothing wrong with newly minted graduates - what the y've been taught isn't usually all that useful, but the good ones have foun d out how to find what they need to know. Universities don't seem to be ent irely aware that they impart this skill, and don't seem to have found out a ny way to test for it, but it's what universities are actually good for.

I wasn't needling Bill, if that's what you mean. After numerous tries I gav e up and killfiled him ages ago. (Or rather added him to a Tbird filter tha t automatically marks a few people's posts as having been read. On Google I have to skip them manually, but it's a habit by now.)

Cheers

Phil Hobbs

ave up and killfiled him ages ago. (Or rather added him to a Tbird filter t hat automatically marks a few people's posts as having been read. On Google I have to skip them manually, but it's a habit by now.)

Dear me. Jim Thompson I'm not worried about, but having Phil Hobbs kill-fil e me is bit depressing.

what's the thermal equivalent of a non-grounded capacitor ?