Yet Another Big Lie

Another big lie is: “Carbon dioxide causes global warming.”

But I don’t think that this actually started out as a lie. I think it’s something that became a lie. And it became a lie when it became an unquestionable political dogma, thanks to politicians like Al Gore.

I think it began life when Carl Sagan showed that the 95% carbon dioxide atmosphere of Venus had resulted in its temperature rising to 460º C. Venus is Earth’s sister planet, and so people started wondering if the same thing could happen on Earth.

And it seems that when it was found from ice cores that carbon dioxide concentrations in the Earth’s atmosphere had risen at the end of the last ice age, over 12,000 years ago, some climate scientists began to think that this was why the ice had all melted back then.

It seems that they simply couldn’t think of any other explanation for it. The Sun hardly ever varies in brightness, and the Earth’s orbit is not far off circular, and the warming and cooling due to the Milankovitch orbital cycles was insufficient to melt the ice. It had to be something else. So they started thinking that the increase in carbon dioxide at the end of the last ice age, combined with feedbacks from other sources, had to be the explanation.

I have a copy of Principles of Planetary Climate by Raymond Pierrehumbert, and although he doesn’t actually assert that the last ice age was ended by carbon dioxide-driven global warming, he does believe that carbon dioxide played a part in the melting of the ice, and he also believes that low levels of carbon dioxide can cause new ice ages to start. And he’s also a global warming alarmist who writes for RealClimate.

So I think that the belief that the last ice age was ended by rising carbon dioxide levels is something that a lot of climate scientists truly believe. And their perfectly rational worry is that now that carbon dioxide levels are rising again, it could result in the last remaining ice on the surface of the Earth melting, and raising sea levels by 60 or 70 metres. After all, if it’s happened once, it can happen again.

Having got very interested in all this for the past 18 months, I’m actually rather more worried that the Earth’s current 12,000 year long warm interglacial period is about to (in the next few thousand years) come to an end, and a new ice age is about to begin. After all, it’s what’s been happening for the past few million years: long ice ages punctuated by brief interglacials. Shouldn’t we be more worried about that?

But nobody seems to be in the least bit worried about the return of the ice. Why not? The answer would seem to be that, because they believe that rising carbon dioxide levels melted the ice 12,000 years ago, rising carbon dioxide levels today will prevent any new ice age from starting anytime soon. Instead they’re far more worried that rising carbon dioxide levels will melt the little remaining ice on the  Earth.

And the very last thing they’re interested in is the tiny 70 milliWatts/m² heat flow from the interior or the Earth, Pierrehumbert page 7:

Once a solid crust forms, the flow of heat from the interior of the Earth to the surface is sharply curtailed, because the heat diffuses very slowly through solid rock. In this situation, supply of heat from the interior becomes insignificant in comparison with the energy received from the Sun, and the Earth has settled into a state where the climate is determined by much the same processes that determine today’s climate: a competition between the rate at which energy is received from the Sun and the rate at which energy is lost to space by radiation of infrared light. This is very likely to have been the case 4.4 billion years ago, if not earlier (my added emphases)

Perhaps the explanation is that Pierrehumbert believes that “the Earth has settled into a [steady] state.” Pierrehumbert clearly thinks in terms of equilibrium steady states. But these equilibrium steady states are entirely imaginary mathematical conveniences. The real world is constantly changing all the time, and the same goes for the ground beneath our feet as for the atmosphere above our heads.

And I’ve been building a simple dynamic heat flow model of the interior of the Earth (I once spent about seven years building similar dynamic heat flow models), and I don’t see any equilibrium steady states at all.

What I find happening is that when snow, which is a very good thermal insulator, builds up on the surface of the Earth, the rocks beneath it gradually warm up, and eventually melt the overlying snow, after which the rocks cool back down until snow can again start to settle and start building up on top of it. It’s a cycle that automatically repeats over and over again:

In the above automatically-repeating cycle the air temperature rises by 9º C when the snow melts at the start of an interglacial period, because the albedo (reflectivity) of the Earth falls when it is no longer covered in snow, and it absorbs sunlight. During the first 10,000 year interglacial period, surface rock temperatures fall, and the air temperature drops by 9º C when the continually-falling snow finally settles and builds back up to 50 metres in depth, and most sunlight is reflected back into space. And then the surface rocks beneath the snow start heating up again, with the top surface layer rising by about 3º C, and re-melting the snow. And so on, indefinitely.

There’s nothing in the least bit “settled” about this. All the temperatures are oscillating up and down over very long periods of time. But you’ll never see this if you use a steady state equilibrium heat flow model.

In my model, the snow melts because the rock beneath it warms up, not the atmosphere above it. And that’s what I think melted the ice at the end of the last ice age 12,000 years ago, not carbon dioxide in the atmosphere. And if carbon dioxide didn’t end the last ice age, it probably won’t stop the next ice age from starting either.

About Frank Davis

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