Saturday, 1 August 2020

Once more unto the motherlode...

From Skeptical Science, another failed debunking which is so piss-poor that it makes whatever it is they are trying to debunk seem more plausible:

Over the last half million years, our climate has experienced long ice ages regularly punctuated by brief warm periods called inter-glacials. Atmospheric carbon dioxide closely matches the cycle, increasing by around 80 to 100 parts per million as Antarctic temperatures warm up to 10°C.

Undisputed so far.

Why do we have Ice Ages? To cut a long story short, the most likely explanation is that seemingly minor changes in Earth's orbit keep summers a bit cooler, so glaciers don't melt back in summer as much as they advance in winter. Glaciers reflect more sunlight back to space, which cools thing down further, and so on. Brrr, shit, Snowball Earth, half of everything dies.

Ice Ages end for the equal and opposite reason. From the mother lode:

Inter-glacials come along approximately every 100,000 years. This is called the Milankovitch cycle, brought on by changes in the Earth's orbit... The combined effect of these orbital cycles cause long term changes in the amount of sunlight hitting the earth at different seasons, particularly at high latitudes.

For example, around 18,000 years ago, there was an increase in the amount of sunlight hitting the Southern Hemisphere during the southern spring. This lead to retreating Antarctic sea ice and melting glaciers in the Southern Hemisphere.(Shemesh 2002). The ice loss had a positive feedback effect with less ice reflecting sunlight back into space (decreased albedo). This enhanced the warming.

That's all you need to know, really. [Something] has an effect, the opposite of [something] has the opposite effect.
What does this have to do with atmospheric CO2?

CO2 actually lags temperature by around 1,000 years. While this result was predicted two decades ago (Lorius 1990), it still surprises and confuses many. Does warming cause CO2 rise or the other way around?

As the Southern Ocean warms, the solubility of CO2 in water falls (Martin 2005). This causes the oceans to give up more CO2, emitting it into the atmosphere. The exact mechanism of how the deep ocean gives up its CO2 is not fully understood but believed to be related to vertical ocean mixing (Toggweiler 1999).

The process takes around 800 to 1000 years, so CO2 levels are observed to rise around 1,000 years after the initial warming (Monnin 2001, Mudelsee 2001).

So warming increases the amount of CO2 in the atmosphere, and cooling reduces it for the equal and opposite reason. There's a significant time lag either way (also appears to be undisputed).

The answer to their question is therefore obviously that warming causes CO2 levels in atmosphere to rise, and cooling causes it to fall. That explains everything, job done, you'd think.
However, they answer their own question with "In actuality, the answer is both."

What? How?

The outgassing of CO2 from the ocean has several effects. The increased CO2 in the atmosphere amplifies the original warming. The relatively weak forcing from Milankovitch cycles is insufficient to cause the dramatic temperature change taking our climate out of an ice age (this period is called a deglaciation). However, the amplifying effect of CO2 is consistent with the observed warming.

It's strange that orbital changes are sufficient to trigger an ice-age (which is a feedback thin), but not strong enough to trigger the reverse (the feedbacks work in reverse). If you are going to do propaganda, then at least be consistent. They (whoever 'they' are) will have to add "falling atmospheric CO2 levels"' to the list of generally accepted reasons of why Ice Ages are as cold as they are and rewrite a lot of text books.

Which isn't beyond them, of course, but it all takes time to falsify.


Robin Smith said...

Persuasion is all about the tools used to change people's minds, without the use of facts and reason.

This applies to LVT as much as climate doctrine.

And it's the way the world changes, always. Don't take it personally or get angry that's it's so unfair. Adopt that gnosis and see your dreams fulfilled

Physiocrat said...

Milankovitch cycles are complicated.
At the moment, it so happens that the earth is closest to the sun at around the time of the northern hemisphere winter solstice.
The earth's axis of inclination varies between about 21 and 25 degrees over the course of one of the cycles. The north pole receives more solar radiation than the equator on midsummer's day.
Milankovitch was a Serb who tried to sort out the mess which is the church calendar - there are currently three options. In the Serbian and Russian churches, Easter is sometimes drifting into early May - it is thirteen days late at the moment.

Physiocrat said...

Robin - fun and making silly ideas look silly, but gently, is a good persuasive tool. There was some good work done by Hillel Steiner on this tack.