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.
Hi there Jennifer,
You posed some very interesting questions. I have another, is it likely that places like Europe and the UK are getting freak heatwaves?
Or are the heatwaves normal but people are hyper sensitive to anything looking like climate predictions of doom are true?
Hi Phillip
Thanks for taking the time to comment, but it does actually matter where on the planet and at what altitude. I thought it was generally agreed from the IPCC to Garth Paltridge and John Nicol that there is hardly any water vapour relative to C02 in the stratosphere.
In the troposphere, water vapour does dominate.
In the stratosphere, with water vapour so low, CO2 becomes the primary infrared emitter. This is central to why increased CO2 causes stratospheric cooling via enhanced emission to space.
Garth Paltridge’s work on declining upper-tropospheric specific humidity (from NCEP data) is relevant here — drier conditions aloft can affect how much water vapour crosses into the stratosphere and thus the radiative balance.
And I wonder how this was all upset at least temporarily with the Hunga Tonga volcano that blasted a lot of water into the stratosphere.
Although we know that the ice-ages and their retreat occurred we cannot be sure of the global event(s) that actually kickstarted the rapid swings to global cooling or warming. The increase in atmospheric CO2 immediately prior to an ice age event as demonstrated in ice cores tends to suggest that cooling of the stratosphere and its impact on global atmospheric circulation warrants closer examination and does explain the rapid swings to glacial or inter-glacial conditions.
Hi Christine,
Thanks so much for your very relevant comment and questions, given the nightly news. And my apologies that your comment was only just discovered in the spam folder, with a few others relating to other threads. Thanks for your patience.
Regarding your question:
Europe may be as hot now as it was 1,000 years ago, during the Medieval Warm Period. So, it is not perhaps surprising if records are being broken given the instrumental record only goes back at most a few hundred years.
That said, measurement methods have changed over recent times and electronic probes have shorter response times which is definitely an issue with the BOM’s measuring system here in Australia though I think the Met Office in the UK is averaging to negate this to some extent.
To be sure, records were once based on measurements from mercury thermometers that have slower response times due to the thermal mass of the glass bulb and mercury, now they are recorded from electronic probes that are extremely sensitive and will have been calibrated to something.
So, new records could in part be attributable to more sensitive and more responsive equipment.
Then there is the issue of UHI-influenced locations.
New official record temperatures are more likely to be from measuring stations at airports with more and more traffic generating its own heat/exhausts and more and more tarmac creating local warming additional to regional and global increases.
UHI is shorthand for the Urban Heat Island/UHI effect, that is known to result in temperatures typically 1-2 degrees Celsius warmer on average for cities like London. Then you can add something like a wind break or a tarmac.
The north side of my brick house gets sunshine and is often radiating warmth even after the sun has gone down. This is a type of UHI. On a sunny and cold day/afternoon/evening it is nice to lean against that wall, because it is that much warmer than everywhere else.
What measurements are available for the CO2 content in the Stratosphere? CO2 (MW ~44) is heavier than “air” (MW ~29) and more than twice that of H2O (MW ~18). Without measurements this is simply a hypothesis.
Hi Bruce
Thanks for your comment and question. I am not across the data sets of C02 content in the stratosphere as you request. My specific measurement expertise relates to temperatures at the surface.
I understand they are extensive, mostly from my previous correspondence with people like John Nicol and especially Garth Paltridge worked with this data.
Specifically these so-called sceptics, and also I understand more mainstream climate scientists would agree:
The molecular weight difference is real, but it is overwhelmed by atmospheric mixing processes.
Turbulent mixing and eddy diffusion in the troposphere and across the tropopause dominate over gravitational settling. These processes stir the atmosphere on timescales of days to weeks — far faster than any slow settling of heavier molecules.
Gravitational separation of gases only becomes significant above the homopause (~80–100 km altitude), where molecular diffusion takes over. Below that, the atmosphere is considered well-mixed for CO₂.
There needs though, to be better understanding that there is strong latitudinal and seasonal gradient in terms of sources of CO₂.
Large-scale circulation (the Brewer-Dobson circulation) slowly transports air from the tropical troposphere into the stratosphere, carrying CO₂ with it.
In practice, observations show CO₂ is one of the most uniformly distributed trace gases up through the mesosphere. Water vapour, by contrast, varies enormously because it can condense and is strongly controlled by temperature.
This is well above my pay grade, but I think too much emphasis is put on CO2.. whereas I think CO2 plays an important part in the weather pattern, maybe I’m off the subject, just my opinion