Dear Ken,
The problem is after the initial injections, i.e. the second yea of GE,
can we even create new particles with a background now 15 to 25 times
higher with or with out nucleation sites? Under the present sulfate
schemes it appears not. in order to "tune in" particle size and number
ternary nucleation of sulfate, water and perhaps ammonia (NH3) will
probably need top be invoked. Let us remember that water vapor is not
finite in the stratosphere and as more particles are produced additional
sulfate will be needed to reduce the vapor pressure of the aerosols. An
additional species such as NH3 could help over come this limitation.
Injection of H2S would lead to greater dispersion of sulfur, allowing
more particle growth but is not considered in stratospheric SRM paper to
date because the microphysics involved in most modeling studies has not
yet been considered.
The actual formation of particles in models of the stratosphere as a
result of geoengineering has yet to be established. This is it greatest
priority of SSRM at this time.
Sincerely,
Oliver Wingenter
On 10/17/2010 3:41 PM, Ken Caldeira wrote:
Yes, you could produce even more new particles yourself which would
inhibit new particle production from someone else's emissions, but
presumably the total particle count would be higher at the end of all
of this than if you did not intervene.
Would it be possible to act on someone else's particle production in a
way that would lower overall particles counts?
On Sun, Oct 17, 2010 at 1:50 PM, Oliver Wingenter
<[email protected] <mailto:[email protected]>> wrote:
Dear Josh,
If the concentration of background particle were large enough, a
few hundred particle per cm3, then this would inhibit new particle
production. At least this is case in the marine boundary layer.
I understand that stratospheric microphysical models are having
trouble making new particles. However, adding NH3 would allow
ternary nucleation tens of thousands of times faster than sulfuric
acid and water alone as is seen in the free troposphere.
In terms of a volcanic eruptions like Pinatubo, I wonder how much
ash made it to the stratosphere and provided nucleation sites?
Sincerely,
Oliver Wingenter
On 10/17/2010 12:29 PM, Ken Caldeira wrote:
Multiple, independent injections would /decrease /the likelihood
of coagulation relative to injecting it all in one place.
Of course, there is potential for coordinated injections to
decrease coagulation (aggregation) relative to uncoordinated
injections.
There is no evidence that I know of that one injection could
"cancel out" the effects of another injection. It seems that the
main case is that the climate effect of A+B would be less than
the climate effects of A plus the climate effects of B.
It is an interesting research question to understand whether
there are countermeasures that would decrease the effectiveness
of injection by injecting something upwind from an injection site
that would promote aggregation of the injected material.
___________________________________________________
Ken Caldeira
Carnegie Institution Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA
+1 650 704 7212 [email protected]
<mailto:[email protected]>
http://dge.stanford.edu/labs/caldeiralab @kencaldeira
On Sun, Oct 17, 2010 at 10:43 AM, Josh Horton
<[email protected] <mailto:[email protected]>> wrote:
Hi everyone,
I am finalizing a chapter on geoengineering policy for
publication and
would greatly appreciate informed feedback on the following
paragraph:
"The aerosol most commonly suggested for stratospheric
injection is
sulfuric acid. Plans call for delivering sulfate aerosols by
dispersing gas-phase precursor materials. Precursor
oxidation and
aerosol formation involve complex processes with the potential to
reduce the effectiveness of stratospheric insertion. For
instance,
coagulation could lead to excessively large sulfuric acid
particles
that sediment out of the stratosphere, neutralizing the
effect of the
initial dispersion. Multiple, independent injections would
increase
the likelihood of such unintended consequences. Unsynchronized
staging, scheduling, and delivery of sulfate aerosol
injections would
magnify the potential for perverse particulate interactions,
and might
jeopardize the success of geoengineering deployment. Lack of
policy
coordination may result in separate injection schemes that
effectively
cancel each other out."
For those with scientific/technical backgrounds, is this a sound
argument? Is the basic science correct? I am outside my
comfort zone
with this and want to be sure I don't miss the mark. Thanks
to anyone
who can offer insight.
Josh Horton
[email protected] <mailto:[email protected]>
http://geoengineeringpolitics.blogspot.com/
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