Stratospheric Radiative Cooling from CO₂

The stratosphere has been cooling over recent decades as atmospheric CO₂ has risen. This occurs because CO₂ in the cold, thin air of the stratosphere becomes more efficient at radiating infrared energy upward into space.

I understand alarmists and sceptics alike, that they both agree on this.

To maintain energy balance, the stratosphere cools.  And this occurs regardless of whether the extra CO₂ comes from human activity or natural sources including ocean outgassing.

This cooling effect could be compounded by an increase in stratospheric aerosols, and here I am specifically thinking of the geo-engineering that is already happening in the UK.

Aerosols also cool the stratosphere, both by reflecting some incoming sunlight and by altering the radiative balance.

When both higher CO₂ and increased aerosols are present, my first question is will the cooling in the stratosphere become stronger than from either factor alone?

Will this combination change stratospheric temperatures, circulation patterns, and potentially the strength of the polar vortex, which can influence weather systems in the lower atmosphere?  (There are a few questions in that.)

This issue, that I have been pondering, concerns weather phenomena that I have not previously thought a lot about.  This is in part perhaps because I have always lived in more tropical areas, perhaps less affected by changes in the stratosphere.

And I wonder whether a similar combination of factors (more aerosols and more CO₂) may have played a role at the end of the last ice age. Around 16,000 years ago, as the great ice sheets began to melt and sea levels rose rapidly, the reduction in ice cover is thought to have increased volcanic activity through crustal unloading.

Another question: Which are the best technical papers on all of this?

Did this led to:

1. Greater volcanic degassing of CO₂ into the stratosphere,
2. More aerosols into the stratosphere,
3. Oceans also degassing CO₂ with the global warming.

The resulting combination of rising CO₂ and increased stratospheric aerosols could have contributed to changes in stratospheric temperatures and circulation during this period of rapid climate transition.

What effect would this have had on global temperatures?

Last year I spent a lot of time thinking about the different components of weather and climate. I put this together sketching out the ‘six planks’ of climate resilience.

I am now thinking of adding ‘Stratospheric CO₂ Radiative Cooling’ as my seventh plank.

While Milankovitch cycles set the stage for glacial-interglacial transitions, they don’t fully account for the speed, magnitude, or mechanisms of events like the 120 metres of sea level rise beginning some 16,000 years ago.

Milankovitch-driven insolation changes are relatively small. While sufficient to perhaps initiate ice sheet retreat, they struggle to explain the massive ice volume loss required for a 120-meter sea level rise.

I remember one email from last year, lamenting my focus on C0₂.  A learned scholar, an expert in metrology (the study of measurement), wrote from Germany:

“Why let yourself be dragged into unimportant questions? CO₂ has negligible influence on the climate. Climate is controlled by solar activity (and finally probably by the planets). Period!”

But what about stratospheric CO₂  radiative cooling?

What do you think?