The response of terrestrial ecosystem carbon cycling under different aerosol-based radiation management geoengineering

[Andrew Lockley]

https://esd.copernicus.org/articles/12/313/2021/

Earth Syst. Dynam., 12, 313–326, 2021

https://doi.org/10.5194/esd-12-313-2021

© Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License.

Research article | 11 Mar 2021

The response of terrestrial ecosystem carbon cycling under different aerosol-based radiation management geoengineering

Hanna Lee et al.

Show author details

Received: 20 Jul 2020 – Discussion started: 31 Jul 2020 – Revised: 09 Feb 2021 – Accepted: 10 Feb 2021 – Published: 11 Mar 2021

Abstract

Geoengineering has been discussed as a potential option to offset the global impacts of anthropogenic climate change and at the same time reach the global temperature targets of the Paris Agreement. Before any implementation of geoengineering, however, the complex natural responses and consequences of such methods should be fully understood to avoid any unexpected and potentially degrading impacts. Here we assess the changes in ecosystem carbon exchange and storage among different terrestrial biomes under three aerosol-based radiation management methods with the baseline of RCP8.5 using an Earth system model (NorESM1-ME). All three methods used in this study (stratospheric aerosol injection, marine sky brightening, cirrus cloud thinning) target the global mean radiation balance at the top of the atmosphere to reach that of the RCP4.5 scenario. The three radiation management (RM) methods investigated in this study show vastly different precipitation patterns, especially in the tropical forest biome. Precipitation differences from the three RM methods result in large variability in global vegetation carbon uptake and storage. Our findings show that there are unforeseen regional consequences under geoengineering, and these consequences should be taken into account in future climate policies as they have a substantial impact on terrestrial ecosystems. Although changes in temperature and precipitation play a large role in vegetation carbon uptake and storage, our results show that CO2 fertilization also plays a considerable role. We find that the effects of geoengineering on vegetation carbon storage are much smaller than the effects of mitigation under the RCP4.5 scenario (e.g., afforestation in the tropics). Our results emphasize the importance of considering multiple combined effects and responses of land biomes while achieving the global temperature targets of the Paris Agreement 

[SALTER Stephen]

Hi All

 

Like several previous workers the authors of the paper, use the accumulation-mode spread of aerosol size between latitudes 45 N and 45 S all the time at a rate to offset RCP 8.5.  

 

The effort or cost needed for marine cloud brightening is in proportion the volume of water that we have to filter and spray.  The value of what the spray does depends on the number of successful nucleations.

 

We think that the right size of aerosol salt particle has a mass of 10^ -14 grams.  If it was a completely dry sphere its diameter would be about 200 nanometres but it is more likely to be a brick shape in strong brine.

 

The graph below from Wikipedia shows that 200 nanometres is at the bottom of the slope of the accumulation mode. The top of the accumulation mode is at about 1.2 microns.  The cube of the ratio of diameters is 216. This means that using the full spread of the accumulation mode will involve making some condensation nuclei far bigger, and so more expensive, than we actually need.

 

 

As second reason is that the Stokes drag tending to accelerate a drop in turbulent flow on depends on diameter not projected area while the inertia opposing acceleration depends on the cube.  If drops of spray in a turbulent air stream have a wide spread of inertias they will also have a wide spread of relative velocities and so more chance of coalescence.

 

A third reason in favour of a monodisperse spray is that heavier condensation nuclei will nucleate at a lower relative humidity than lighter ones.  This will suck water vapour from the surrounding air and so reduce its relative humidity and make it harder for the small ones to nucleate.  The transfer rate of water vapour depends of vapour pressure difference and surface area.   Being big earlier than rival nuclei gives a further advantage.  This is the same with wolves and hyenas.

 

It might be convenient for climate modellers to use the wide spread of standard, naturally-occurring aerosol built into modelling software but please, please, please could somebody try monodisperse spray to avoid errors of 200.

Please also give us  an opinion about whether 10 ^ -14 grams is the right choice.  Can we reduce coalescence even further with electrostatic charge?

 

 

Stephen Salter

Emeritus Professor of Engineering Design

School of Engineering

Mayfield Road  EH9 3 DW

University of Edinburgh

Scotland.

Tel 0131 662 1180

 

From: geoengi...@googlegroups.com <geoengi...@googlegroups.com> On Behalf Of Andrew Lockley
Sent: 11 March 2021 21:14
To: geoengineering <geoengi...@googlegroups.com>; CarbonDiox...@googlegroups.com <CarbonDiox...@googlegroups.com> <carbondiox...@googlegroups.com>
Subject: [geo] The response of terrestrial ecosystem carbon cycling under different aerosol-based radiation management geoengineering

 

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[NORTHCOTT Michael]

Hi all

Seeing that sunspots are down 77% 2019-20 and a paper has already been published in the journal Temperature indicating that a new Grand Solar Minimum has begun and will cause cooling of 1 degree C until 2050 the case for geoengineering is surely over. The last GSM ended in 1821 after causing glaciers to advance and giving rise to famines because of significantly reduced crop production. See Valentina Zharkova, ‘Modern Grand Solar Minimum will lead to

terrestrial cooling’ Temperature 7.3 2020. 

https://doi.org/10.1080/23328940.2020.1796243

Michael Northcott

Emeritus Professor of Ethics

University of Edinburgh

---

From: geoengi...@googlegroups.com <geoengi...@googlegroups.com> on behalf of SALTER Stephen <S.Sa...@ed.ac.uk>
Sent: Saturday, March 13, 2021 00:20
To: andrew....@gmail.com; geoengineering; CarbonDiox...@googlegroups.com <CarbonDiox...@googlegroups.com>
Cc: Alan Gadian
Subject: RE: [geo] The response of terrestrial ecosystem carbon cycling under different aerosol-based radiation management geoengineering

 

To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/PR3PR05MB735411D4E40D5FE6C679C775A76F9%40PR3PR05MB7354.eurprd05.prod.outlook.com.

[SALTER Stephen]

Hi All

 

I got this from Wikipedia

 

 

 

 

 

Stephen Salter

Emeritus Professor of Engineering Design

School of Engineering

Mayfield Road  EH9 3 DW

University of Edinburgh

Scotland.

Tel 0131 662 1180

 

[Daniele Visioni]

Valentina Zharkova is very well known for publishing bogus science on the connection between solar activity and climate.

Her last paper in SciRep was retracted one week after publication https://www.nature.com/articles/s41598-020-61020-3

The one article linked is an editorial in a journal whose scientific scope is “ medical physiology of body temperature regulation,”

Further, there is plenty of discussion of the relationship between the Maunder Minimum and the little ice age (which was also most likely a local, NH phenomena), as the onset of the MM happened in the middle of the ice age. See for instance this study discussing the causes of the LIA.

https://news.agu.org/press-release/unusual-volcanic-episode-rapidly-triggered-little-ice-age-researchers-find/

So no, the Sun is very, very unlikely to be able to save us from our own mess.

On 14 Mar 2021, at 08:11, SALTER Stephen <S.Sa...@ed.ac.uk> wrote:



Hi All

 

I got this from Wikipedia

 

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