Overshoot

[Stephen Salter]

Hi All

The Nature paper by Richard Lovett at

https://www.nature.com/articles/d41586-023-01725-3?WT.ec_id=NATURE-202306&sap-outbound-id=DD2C61054D98C5BDD2C13072933E43E6D8C8E8F2

will annoy advocates for stratospheric sulphur more than those for marine cloud brightening.

It is a surprise to see this in Nature.

Stephen

 

Emeritus Professor of Engineering Design

School of Engineering

University of Edinburgh

Mayfield Road

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Scotland

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YouTube Jamie Taylor Power for Change

 

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[Clive Elsworth]

Hi Stephen – and cloud experts

 

I found this paper educational, by Shupe et al, 2004: Cloud Radiative Forcing of the Arctic Surface: The Influence of Cloud Properties, Surface Albedo, and Solar Zenith Angle:  https://journals.ametsoc.org/view/journals/clim/17/3/1520-0442_2004_017_0616_crfota_2.0.co_2.xml

 

It says low level clouds in the Arctic only provide cooling during a short period during the summer. The rest of the year they warm the Arctic. So presumably, as increasingly warmer seas flow into the Arctic these clouds will get thicker (i.e. greater Liquid Water Path – LWP) because the air will be more humid, making each cloud droplet bigger. So, it seems that to cool the Arctic the oceans need to be cooled.

 

Have I got that right?

 

Clive

 

From: noac-m...@googlegroups.com <noac-m...@googlegroups.com> On Behalf Of Stephen Salter
Sent: Thursday, June 1, 2023 2:18 PM
To: 'geoengi...@googlegroups.com' <geoengi...@googlegroups.com>; 'noac-m...@googlegroups.com' <noac-m...@googlegroups.com>
Subject: Overshoot

 

Hi All

The Nature paper by Richard Lovett at

https://www.nature.com/articles/d41586-023-01725-3?WT.ec_id=NATURE-202306&sap-outbound-id=DD2C61054D98C5BDD2C13072933E43E6D8C8E8F2

will annoy advocates for stratospheric sulphur more than those for marine cloud brightening.

It is a surprise to see this in Nature.

Stephen

 

>Nature - Overshoot

Yes a surprise, especially as it’s so easy to avoid another glacial period.

Clive

 

 

Emeritus Professor of Engineering Design

School of Engineering

University of Edinburgh

Mayfield Road

Edinburgh EH9 3DW

Scotland

0131 662 1180

YouTube Jamie Taylor Power for Change

 

The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. Is e buidheann carthannais a th’ ann an Oilthigh Dhùn Èideann, clàraichte an Alba, àireamh clàraidh SC005336.

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[Achim Hoffmann]

Cooling the Oceans is a no-brainer, if it can be done.

 

There were a few recent publications talking about melting from “below”.

 

Here a recent WWF post including a Video explainer clearly targeted at the wider public (rather than experts).

https://www.arcticwwf.org/the-circle/stories/omg-greenlands-glaciers-are-melting-from-below/

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[Stephen Salter]

Clive

It is true and also rather obvious that cloud brightening only works in summer and this is taken in the calculations about the number of spray vessels which I have circulated. Please let me know if you would like me to send them again.

I agree that warm water in winter would be bad and so we should do marine cloud brightening at lower latitudes through the year.  This is a strong argument for vessel mobility.  The cooling will still be done but with a time delay.

If the Alterskjaer and Kristjansson are correct about Aitken mode aerosol  warming by clearing clouds because it removes lots of water without nucleation, then it might be possible to clear clouds in winter by spraying the very small aerosol.  The old design of spray vessels had 18 spray heads.  The present one has 32 so we could use smaller nozzles for part of the year.  We could also dilute salt water with some desalinated water or take water from what has melted from Iceland. It is only the mass of salt in the aerosol that matters.

 

Below are graphs from Curry about radiation levels through the year. Please let me know if you have any more recent data.

 

Stephen

 

 

From: noac-m...@googlegroups.com <noac-m...@googlegroups.com> On Behalf Of Achim Hoffmann
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Subject: RE: Clouds in the Arctic only provide cooling during a short period during the summer

 

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[Clive Elsworth]

Thanks Stephen

 

I was wondering if anything other than cooling the flow of the oceans into the Arctic could help to cool Greenland ice outside the short period when MCB would work.

 

If droplet scavenging turns out to be effective, we may be able to do it over Greenland from drones or land-based stations, using our non-toxic white coloured Artificial Loess Dust aerosol that forms from vaporous chlorides and degenerates to clay after sedimenting.

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[rob...@rtulip.net]

Hi Clive

 

I was chatting this week with Stephen Salter about Marine Cloud Brightening at different latitudes.  It is a misconception, which I also shared, that directly cooling ocean currents flowing into the Arctic offers the main potential intervention for refreezing.  The main global cooling potential, including for the poles, is in cooling the tropics.   

 

Only about 15% of the Earth (~75 million km²) is north of 45° North latitude.   As well as being far smaller than the tropics, the high latitude regions are obviously far colder and darker, and therefore cannot be cooled as much as hotter regions. 

 

Applying marine cloud brightening in the tropics can refreeze the poles through the combination of cooler currents and cooler air temperature circulating to the poles.  High latitude MCB is also essential, given the combination of arctic amplification and that summer insolation is highest at the poles, but this seasonal polar warmth is relatively small and brief on global scale.   Stephen also pointed out that GEOMIP models that restrict MCB to the band within 30° of the equator fail to recognise the importance of also deploying salty mist at higher latitudes.

 

Like a Mercator Projection, the political sway of the cold north seems to inflate its size in our imagination.

 

Regards

 

Robert Tulip

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[Cl...@endorphinsoftware.co.uk]

Hi Robert

 

I remember learning about heat capacity in physics at school. In my brevity I was unclear. I’m fully aware that you can’t use brighter clouds to sufficiently cool water that is rapidly flowing from a warmer ocean into the Arctic. In my presentation for Tuesday’s CCRC conference there is a section on cooling the oceans that mentions marine cloud brightening.

 

It also introduces the idea of terrestrial cloud brightening (and potentially thinning) using artificial loess dust. If cloud brightening is going to become an important way to stabilise the climate then we want to have more than one tool in the toolbox.

 

Cooling the oceans with clouds from phytoplankton, boosted by diffuse fertilisation by iron salt aerosol is also mentioned. That is another method of mimicking the loess dust, which was more prevalent in the air during the last glacial period as seen in ice cores.

 

Clive

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