SG and Tropical Monsoons

[Govindasamy Bala]

Dear All,

In this paper that came out last week in Climate Dynamics, we looked at the changes in mean precipitation in tropical monsoon regions for sulfate injections at different latitudes. 

Key message: India could experience persistent droughts if aerosols are injected at 15 or 30 deg N. The result is interpreted from planetary energetics and interhemispheric asymmetry in energy balance. 

Many of you may be aware that Ben Kravitz, Doug, Simone and others have worked on ideas such as controlled injections at several locations simultaneously to avoid such catastrophes, but I am not sure we can really have such precise control on the climate system....

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With Best Wishes,

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G. Bala
Professor
Center for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore - 560 012
India

Tel: +91 80 2293 3428; +91 80 2293 2505
Fax: +91 80 2360 0865; +91 80 2293 3425
Email: gb...@iisc.ac.in; bala.gov@gmail.com
Google Scholar
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[Douglas MacMartin]

Hi Bala,

Agree that we need to better understand the impact of different choices, but I'm not sure why you think it is "precise control" to avoid injection into a single hemisphere?  We've known for a long time that doing something like only injecting at 15N would be a bad idea, so hopefully no-one will do that (and if someone did, and diplomacy weren't enough to dissuade them, then some other actor should develop simultaneous capability to inject at 15S; in that sense I don't think a sustained significant deployment at 15N is a remotely plausible scenario as it would require an actor so driven to damage the tropics that they are willing to use military force to block any other actor from deployment).

Here's a hypothesis (broadly similar to the sort phrased by Peter Irvine and David Keith): In any climate model, a symmetric injection (whatever you do in one hemisphere, do the same in the other) sufficient to cool by ~1C (so 2C warming --> 1C, or 2.5 --> 1.5C) will not lead to changes in monsoon precipitation that are detectably outside the range of historical values.  That seems eminently testable.

I do agree that the sorts of feedback control algorithms we used in GLENS, for example, are purely modeling tools and not representative of the adjustment strategies that would occur in a real deployment (which would likely be more based on updating climate models based on observations and making new projections of different strategies)

doug

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[Cush Ngonzo Luwesi]

Dear Bala et Al.

These predictions are acurate and concur with many recent experiments following the famous Robock (2008): ''Twenty reasons why Geoengineering is a Bad idea''. Now We need strong policy measures to prevent Such catastrophies at a global scale.

Kudos!

[Haywood, James]

Hi All,

I'm with Doug on this one. It would be pathological to inject solely into one hemisphere. The original paper that looked at this (almost a decade ago, Haywood et al., 2013 although there are plenty of papers before this examining impacts of explosive volcanic eruptions - e.g. Luke Oman and Alan Robock's work) showed that there are important detrimental impacts on the ITCZ and associated rainfall should injections occur in one hemisphere. There are a bunch of other papers that look at the energetics of preferential heating one hemisphere in the HadGEM3 model (Haywood et al., and Hawcroft et al papers), plus a whole host of others with other models that show that perturbing the energy balance and hence the temperature in one hemisphere will lead to shifts in the ITCZ.

In many ways the "injections in one hemisphere only" simulations were designed to head-off the idea that was mooted at the time that the current fleet of civil aircraft could be used as an effective climate intervention strategy. Having worked in this area for a while, I should stress that such injection strategies are rather pathological.

What Doug (and others) have done is to develop feedback controllers that inject at multiple latitudes, and one of the primary objectives is to ensure that the northern and southern hemisphere coolings are similar to prevent any such detrimental impacts on the ITCZ and associated rainfall.

Best Regards

Jim

  

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From: geoengi...@googlegroups.com <geoengi...@googlegroups.com> on behalf of Cush Ngonzo Luwesi <cushn...@gmail.com>
Sent: 12 January 2022 09:41
To: bala...@gmail.com <bala...@gmail.com>
Cc: geoengineering <geoengi...@googlegroups.com>; Geoeng Info <infog...@gmail.com>; Andrew Lockley <andrew....@gmail.com>
Subject: Re: [geo] SG and Tropical Monsoons

 

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[Alan Gadian]

Dear Jim,

In the “younger dryas” period, the surface heating was different in Northern and Southern Henispheres with interesting consequences.  Worth looking at again. 

Any way injecting in one hemisphere will spread to other hemisphere , albeit slowly, but obs suggest faster than low resolution models indicate as don’t include small scale and mixing processes such as gravity waves et al . 

regards

Alan 

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Alan Gadian,  UK. 

Tel: +44 / 0  775 451 9009 

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On 12 Jan 2022, at 09:57, Haywood, James <J.M.H...@exeter.ac.uk> wrote:



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