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:
- Greater volcanic degassing of CO₂ into the stratosphere,
- More aerosols into the stratosphere,
- 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?
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Whatever CO2 may be doing, wherever it is doing it, it will be a very small fraction of what the H20 will be doing by its presence in very much higher concentrations.
All the matter, land and oceans and atmosphere is absorbing and emitting on the full bandwidth of the electromagnetic radiation inside the bandwidth between very long and very short wavelengths and all the matter is exchanging energy in the form of heat and motion with a tropics to poles drift imposing quite a lag time on the speed of transfer.
Water is the great enigma. It absorbs and emits energy from melting and freezing, from condensing and evaporating without temperature change and with the paradoxical expansion from near freezing which adds a gravitational component to the energy exchange system.
We need engineers to trial models of air-conditioning and refrigeration systems to get anywhere near a crude understanding of the whole system; I wonder if all the current mathematical physics will be capable of dealing with giving us a complete account of the process.
There is no necessary steady state, there is no natural equilibrium but just the most highly probable envelope of rates of change.
Just like a living body, there will be a temperature above which there will be runaway rise and a temperature where there will be runaway freezing.