Hi Andrew,

 

On the first one, yes, there are potentially regional applications of MCB, so 
agree with you on that.  (I don’t think there are hemispheric applications of 
SAI; that would screw a lot of people with ITCZ shift, so SAI is only global.)

 

Re the aircraft bit, no, I disagree that SAI can be done stealthily.  The 
aircraft will be different, their flight paths will be different, their 
altitude will be different, and you’d need enough flights that it would be 
pretty easy to spot the flights.  Plus, pretty easy to spot the change in 
stratospheric aerosol concentrations (though that alone wouldn’t give you the 
attribution as to who was doing it, but seeing dozens of airplanes flying up to 
the stratosphere and then landing again might be a hint…)

 

The US was able to keep stealth fighters hidden for a short while because they 
were only flown in very limited locales for limited duration; I don’t think you 
could keep aircraft that you’re constantly flying up to the 20-25km hidden.

 

So the only thing you could do stealthily is a stunt that you subsequently 
reveal for political reasons, rather than a meaningful amount of cooling.  And 
you could do that with MCB if you wanted too.

 

d

 

From: geoengineering@googlegroups.com [mailto:geoengineering@googlegroups.com] 
On Behalf Of Andrew Lockley
Sent: Tuesday, March 13, 2018 5:26 PM
Cc: geoengineering <geoengineering@googlegroups.com>
Subject: Re: [geo] Should we lump MCB & Stratospheric SRM as equally risky?

 

Doug

 

The governance challenges are not identical. MCB is local to regional in its 
immediate impact, potentially of use for regional climate modifications. SAI is 
hemispheric. 

 

>From an accountability point of view, MCB is more traceable. The ships are 
>slow-moving and easy to spot. They don't look like any other ships.

 

By contrast: SAI can be done stealthily, mixed up with regular air traffic, and 
with no visible plume if SO2 used. 

 

A 

 

On Tue, 13 Mar 2018, 20:45 Stephen Salter, <s.h.sal...@ed.ac.uk 
<mailto:s.h.sal...@ed.ac.uk> > wrote:

Andrew

I must object to your claim that the rapid control of marine cloud brightening 
is risky.

Control engineers will tell you that they like systems with a single, dominant 
phase lag. You are right in saying that the effects of marine cloud brightening 
fade quickly but the world's response is set by the very large thermal inertia 
of the oceans acting as a heat store.   This may be a bit slower than the 
effects of stratospheric sulphur on land.

An attractive feature is that we can stop the input signal very quickly 
following an unpredicted volcanic eruption or a new ice age.  We have a degree 
of local and seasonal adjustment.  We can aslo taper off in a controlled way as 
carbon removal technologies ramp up.

People who are worried about termination effects should ask whether they would 
prefer a process which was irreversible.  That would really scare me. 

May I repeat my previous observation that the loss of power generation is 
catastrophic in 20 milliseconds, the internet in two seconds, air traffic 
control in two minutes, water and sewage and food distribution in about two 
days.

Compared with these, ten years is a long time to fix or replace spray vessels.

Stephen

 

On 13/03/2018 18:43, Andrew Lockley wrote:

It's complicated to answer. The MCB fade out period is days not years, so the 
simple answer is that MCB is more risky. But the real answer depends in system 
vulnerability, which in turn depends on a complex interacting network of 
social, political and technical risks 

 

Andrew 

 

On Tue, 13 Mar 2018, 18:30 E Durbrow, <durb...@gmail.com 
<mailto:durb...@gmail.com> > wrote:

Would some kind person tell me if I got these claims wrong? 

 

Marine Cloud Brightening and Stratospheric Aerosol SRM are *not* equivalently 
risky.

 

While both have the possibility of termination shock and regional variation, 
these two risks are lower in MCB. 

 

I’m worried that the discussion on termination shock is treating all SRM 
methods as equivalent…

 

Thanks for pointing me to a publication indicating that MCB and 
Stratospheric/High Altitude SRM are roughly equally risky.

 

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