Dear Mike,
I don't understand this suggestion. Because of the shorter sulfate
lifetime than in the stratosphere (even if it is more than the 1 week
you get for surface injections), you would require a much larger sulfur
injection for the same radiative forcing as compared to the
stratosphere, and a much larger resulting acid deposition in remote
areas. And how could you be guaranteed to maintain the emissions from a
lot of stacks from small enterprises that would keep changing over time
based on business variations and local environmental laws? This seems
to be a much riskier strategy even than stratospheric injections from a
centralized operation.
And why would you think most removal would be in the ITCZ? That would
require the sulfate to enter the ITCZ from the surface in specific
tropical regions.
Alan
Alan Robock, Distinguished Professor
Editor, Reviews of Geophysics
Director, Meteorology Undergraduate Program
Department of Environmental Sciences Phone: +1-848-932-5751
Rutgers University Fax: +1-732-932-8644
14 College Farm Road E-mail: rob...@envsci.rutgers.edu
New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock
http://twitter.com/AlanRobock
Watch my 18 min TEDx talk at http://www.youtube.com/watch?v=qsrEk1oZ-54
On 8/5/2014 2:39 PM, Mike MacCracken wrote:
Re: [geo] A Win-Win research program proposal on SRM (sunlight
reflection methods) Regarding this proposal for sustaining the sulfate
cooling influence, the suggestion on this that I have been making for
several years (see refs below, among others) is similar: rather than
having a relatively high sulfate loading concentrated over populated
areas, inject SO2 above the boundary layer (important to promote a
longer lifetime) to create thinner sulfate layers over much larger
remote areas of the ocean (e.g., over the Pacific and Indian Oceans),
hoping to promote both clear sky and cloudy sky brightness. Doing this
over the ocean would take advantage of its low albedo so that the
sulfates would not be offsetting reflected solar radiation from the
surface. Doing this over larger areas and at lower loadings would tend
to moderate the change in energy in a given area, although there would
need to be testing of this. Most removal might come in ITCZ rains,
mostly over the ocean.
Mike MacCracken
MacCracken, M. C., 2009: Beyond Mitigation: Potential Options for
Counter-Balancing the Climatic and Environmental Consequences of the
Rising Concentrations of Greenhouse Gases, Background Paper to the
2010 World Development Report, Policy Research Working Paper (RWP)
4938, The World Bank, Washington, DC, May 2009, 43 pp.
MacCracken, M. C., 2009: On the possible use of geoengineering to
moderate specific climate change impacts, /Environmental Research
Letters/, *4* (October-December 2009) 045107
doi:10.1088/1748-9326/4/4/045107
[http://www.iop.org/EJ/article/1748-9326/4/4/045107/erl9_4_045107.html].
MacCracken, M. C., 2011: Potential Applications of Climate Engineering
Technologies to Moderation of Critical Climate Change Impacts, IPCC
Expert Meeting on Geoengineering, 20-22 June 2011, Lima, Peru, pages
55-56 in Meeting Report, edited by O. Edenhofer, R. Pichs-Madruga, Y.
Sokona, C. Field, V. Barros, T. F. Stocker, Q. Dahe, J. Minx, K. Mach,
G.-K. Plattner, S. Schlömer, G. Hansen, and M. Mastrandrea,
Intergovernmental Panel on Climate Change, Geneva, Switzerland.
On 8/1/14 8:53 AM, "ecologist" <ecologi...@gmail.com> wrote:
Currently, anthropogenic tropospheric aerosols present both Dr
Jekyll and Mr Hyde faces.
On the one hand, tropospheric aerosols play an important role on
climate, with a net cooling radiative forcing effect.
On the other hand, tropospheric aerosols affect terrestrial
ecosystems and human health and are associated with increased
heart, lung and respiratory diseases, which lead to disablement
and numerous premature human deaths (Shindell et al, 2012).
Consequently, reducing anthropogenic tropospheric aerosols
emissions, on the one hand will lead to a positive forcing
(warming) at local and regional scale, and on the other hand will
save numerous lives and significantly reduce health costs.
*What is proposed is to investigate means whereby the cooling
effect of current emissions is kept unchanged and their
deleterious effects are reduced,* using only modifications of
existing industrial aerosols emitters. Key advantages of such
investigations are that they avoid most of the roadblocks
associated with SRM.
So, what is proposed is a Win-Win research program that will at
the same time allow indirect geoengineering research, and reduce
tropospheric pollution.
/(Important remark: it is not proposed to perform CCS, or CDR).
/
This is so, because the current anthropogenic tropospheric
sulphate aerosol emissions are estimated to be _almost two orders
of magnitude larger_ than requested by Stratospheric Particle
Injection geoengineering schemes to offset the effects of a 2 X
CO2 (carbon dioxide concentration doubling in the atmosphere).
Thus the strategy to reduce current sulphate _tropos_pheric
emissions and at the same time to keep their current cooling
effects will be like performing indirect climate engineering
without the need to artificially inject sulphates in the
_strato_sphere.
Now, the radiative forcing due to sulphate aerosols is estimated
to be -0.4 W/m2 with a range of -0.2 to -0.8 W/m2.
On a global average basis, the sum of direct and indirect
radiative forcing at the top of atmosphere by anthropogenic
aerosols is estimated to be -1.2 W/m2 [-2.4 to -0.6 W/m2]
(*cooling*) over the period of 1750 - 2000. This is significant
when compared to the positive (*warming*) forcing of +2.63 [±0.26]
W/m2 by anthropogenic long-lived greenhouse gases over the same
period [Forster et al., 2007].
In heavily polluted regions, aerosol cooling overwhelms greenhouse
warming [Ramanathan et al., 2001; Li et al., 2010].
The tropospheric aerosol lifetimes are approximately 1 to 2 weeks,
which is quite shorter. Therefore, these current human made
aerosols have an uneven distribution, both horizontally and
vertically, and are more concentrated near their source regions
over continents and in the boundary layer.
*Emission reductions of aerosols in the troposphere will lead to a
positive forcing (warming), unless the sulphates lifetimes are
increased and their horizontal and vertical distribution are
improved. Whilst the particulates are removed, some part of the
sulphates can be lofted higher to where they can act as a
solar-reflective shield to cool larger regions.
*
To do so, what is proposed is to model the effects of a
theoretical fivefold aerosols emission reduction (80% removal of
sulphates, NOx, and > 95% removal of soot, black carbon, ash...)
by adding filters or electrostatic precipitators to the flue stack
of a majority of fossil fuel fired power plants, for adequate
particulate filtering and scrubbing, and *at the same time
increasing the height release of sulphates for a reduced number of
other power plant stacks in order to allow these (20% SOx)
emissions to over pass the boundary layer and stay longer in the
atmosphere*.
This can be__performed by the use of taller chimneys allowing the
flue gases to pass the boundary layer, so that the impact of a
regional emission reduction is not confined to the region itself,
by allows intercontinental transport (long-range transport) of
these sulphates _produced by existing anthropogenic aerosols_.
Several other possibilities exist to increase the height release
and dilution of gas emissions from flue stacks.
*
*This strategy was proposed in page 818-819 of an _open access
article_
http://www.sciencedirect.com/science/article/pii/S1364032113008460
Fighting global warming by climate engineering.
/
Two figures are attached to summarize this research proposal
/
Public perception of SRM climate engineering is often presented as
Ulysses choices between the perils of Scylla and Charybdis,
despite the very good cooling potential to mitigate global
warming, and the high effectiveness and accessibility of
geoengineering schemes consisting of the stratospheric injection
of sulphate aerosols.
The Win-Win strategy proposed here may change this perception at
the same time as helping to advance CE research...
Renaud de_Richter, PhD
http://www.solar-tower.org.uk/
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