Combustion Aerosols as a Source of Bioavailable Iron Re. (Unintended) Ocean Iron Fertilization Climate Geoengineering

By Oscar Escobar - April 30, 2015
Last update September 10, 2015

Recently in an informal conversation with someone dear to me, I was asked to summarize climate geoengineering in 140 characters or words. I took it as meaning one twitt:

SRM and OIF climate geoengineering "we" are already doing it with fossil fuel aerosols but we ignore that fact.

I should have said: 'we like' to ignore that fact.

Two studies that encompass both the Northern and Southern oceans partly explain some of the reasons of why I have arrived at that conclusion. (See full abstracts and links below my comments)

The study centered on the Northern oceans states: 

"Due to continuing growth in global shipping and no regulations regarding particles emissions over the open ocean, the input of potentially bioavailable iron from ship plumes is likely to increase during the next century. The model results suggest suggest that deposition of soluble iron from ships in 2100 contributes 30–60% of the soluble iron deposition over the high‐latitude North Atlantic and North Pacific".

This study prompted the New Scientist article "Sooty ships may be geoengineering by accident"
in which Jeff Hecht writes:

GEOENGINEERING is being tested - albeit inadvertently - in the north Pacific. Soot from oil-burning ships is dumping about 1000 tonnes of soluble iron per year across 6 million square kilometres of ocean, new research has revealed.
 Fertilising the world's oceans with iron has been controversially proposed as a way of sucking carbon dioxide out of the atmosphere to curb global warming. Some geoengineers claim releasing iron into the sea will stimulate plankton blooms, which absorb carbon, but ocean processes are complex and difficult to monitor in tests.
 "Experiments suggest you change the population of algae, causing a shift from fish-dominated to jellyfish-dominated ecosystems," says Alex Baker of the University of East Anglia, UK. Such concerns led the UN Convention on Biological Diversity (CBD) to impose a moratorium on geoengineering experiments in 2010.
 The annual ship deposition is much larger, if less concentrated, than the iron released in field tests carried out before the moratorium was in place. Yet because ship emissions are not intended to alter ocean chemistry, they do not violate the moratorium, says Jim Thomas of the ETC Group, a think tank that consults for the CBD. "If you intentionally drove oil-burning ships back and forth as a geoengineering experiment, that would contravene it." 

The results of the study centered on the Southern oceans:

"suggest that deposition of soluble iron from combustion sources contributes more than 40% of the total soluble iron deposition over significant portions of the open ocean in the Southern Hemisphere". 

My comments:

As I said before here on this blog and in my twitter feed: I think that 'we' are already geoengineering the oceans via iron fertilization (and the atmosphere i.e. SRM in other posts).

Regardless of the Intentionality issue, that implies that all the concerns related to the environment i.e. marine ecosystems, and all the questions of climate justice i.e. responsibilities/liabilities/reparations and all the concerns like those voiced by The Convention on Biological Diversity and groups like the ETC apply. 

Apply but are not governed; and they will not be governed as long as they remain willfully ignored or under the shroud of being 'non-intentional' effects.

The abstracts and links:

Global modeling study of potentially bioavailable iron input from shipboard aerosol sources to the ocean 

Akinori Ito1 Received 2 April 2012; revised 27 September 2012; accepted 4 November 2012; published 18 January 2013. [1] 

Iron (Fe) is an essential element for phytoplankton. The majority of iron is transported from arid and semiarid regions to the open ocean, but it is mainly in an insoluble form. Since most aquatic organisms can take up iron only in the dissolved form, aerosol iron solubility is a key factor that can influence the air‐sea CO2 fluxes and thus climate. 

Field observations have shown relatively high iron solubility in aerosols influenced by combustion sources, but specific emissions sources and their contributions to deposition fluxes largely remain uncertain. Here a global chemical transport model was used to investigate the effect of aerosol emissions from ship plumes on iron solubility in particles from the combustion and dust sources. 

The model results reveal that the oil combustion from shipping mainly contributes to high iron solubility (>10%) at low iron loading (1–110ngm–3 ) observed over the high‐latitude North Atlantic Ocean, rather than the other combustion sources from continental industrialized regions. Due to continuing growth in global shipping and no regulations regarding particles emissions over the open ocean, the input of potentially bioavailable iron from ship plumes is likely to increase during the next century. The model results suggest that deposition of soluble iron from ships in 2100 contributes 30–60% of the soluble iron deposition over the high‐latitude North Atlantic and North Pacific. 

Citation: Ito, A. (2013), Global modeling study of potentially bioavailable iron input from shipboard aerosol sources to the ocean, Global Biogeochem. Cycles, 27, 1–10, doi: 10.1029/2012GB004378.

PDF http://onlinelibrary.wiley.com/doi/10.1029/2012GB004378/pdf

Atmospheric Processing of Combustion Aerosols as a Source of Bioavailable Iron

Akinori Ito *

Yokohama Institute for Earth Sciences, JAMSTEC, Yokohama, Kanagawa 236-0001, Japan

Environ. Sci. Technol. Lett., 2015, 2 (3), pp 70–75

DOI: 10.1021/acs.estlett.5b00007

Publication Date (Web): February 2, 2015

Copyright © 2015 American Chemical Society

*E-mail: akinorii@jamstec.go.jp. Phone: (+81)457785717. Fax: (+81)457785707.

ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

Abstract

Atmospheric processing of combustion aerosols may promote transformation of insoluble iron into soluble forms. Here, an explicit scheme for iron dissolution of combustion aerosols due to photochemical reactions with inorganic and organic acids in solution is implemented in an atmospheric chemistry transport model to estimate the atmospheric sources of bioavailable iron. The model results suggest that deposition of soluble iron from combustion sources contributes more than 40% of the total soluble iron deposition over significant portions of the open ocean in the Southern Hemisphere. A sensitivity simulation using half the iron dissolution rate for combustion aerosols results in relatively small decreases in soluble iron deposition in the ocean, compared with the large uncertainties associated with iron solubility at emission. More accurate quantification of the soluble iron burdens near the source regions and the open ocean is needed to improve the process-based understanding of the chemical modification of iron-containing minerals.

Link: Ihttp://pubs.acs.org/doi/abs/10.1021/acs.estlett.5b00007

Sooty ships may be geoengineering by accident

http://www.newscientist.com/article/mg21729035.100-sooty-ships-may-be-geoengineering-by-accident.html#.VUJaACFViko

One more study:
Added May 3 (My emphasys)

Sources, transport and deposition of iron in the global atmosphere

R. Wang1,2,3, Y. Balkanski1,3, O. Boucher4, L. Bopp1, A. Chappell5, P. Ciais1,3, D. Hauglustaine1, J. Peñuelas6,7, and S. Tao2,3

Abstract. Atmospheric deposition of iron (Fe) plays an important role in controlling oceanic primary productivity. However, the sources of Fe in the atmosphere are not well understood. In particular, the combustion sources of Fe and their deposition over oceans are not accounted for in current biogeochemical models of the carbon cycle. Here we used a mass-balance method to estimate the emissions of Fe from the combustion of fossil fuels and biomass by accounting for the Fe contents in fuel and the partitioning of Fe during combustion. The emissions of Fe attached to aerosols from combustion sources were estimated by particle size, and their uncertainties were quantified by a Monte Carlo simulation. The emissions of Fe from mineral sources were estimated using the latest soil mineralogical database to date. As a result, the total Fe emissions from combustion averaged for 1960–2007 were estimated to be 5.1 Tg yr−1 (90% confidence of 2.2 to 11.5). Of these emissions, 2, 33 and 65% were emitted in particles <1 μm (PM1), 1–10 μm (PM1−10), and >10 μm (PM>10), respectively, compared to total Fe emissions from mineral sources of 41.0 Tg yr−1. For combustion sources, different temporal trends were found in fine and medium-to-coarse particles, with a notable increase in Fe emissions in PM1 and PM1−10 since 2000 due to a rapid increase from motor vehicles. These emissions have been introduced in a global 3-D transport model run at a spatial resolution of of 0.94° latitude by 1.28° longitude to evaluate our estimation of Fe emissions. The modelled Fe concentrations were compared to measurements at 825 sampling stations. The deviation between modelled and observed Fe concentrations attached to aerosols at the surface was within a factor of two at most sampling stations, and the deviation was within a factor of 1.5 at sampling stations dominated by combustion sources. We analyzed the relative contribution of combustion sources to total Fe concentrations over different regions of the world. The new mineralogical database led to a modest improvement in the simulation relative to station data even in dust dominated regions, but could provide useful information on the chemical forms of Fe in dust for coupling with ocean biota models. We estimated a total Fe deposition sink of 8.4 Tg yr−1 over global oceans, 6.6% of which originated from the combustion sources. The higher than previously estimated combustion-related Fe emissions implies a larger atmospheric input of soluble Fe over the northern Atlantic and northern Pacific Oceans, which is expected to enhance the biological carbon pump in those regions.

Citation: Wang, R., Balkanski, Y., Boucher, O., Bopp, L., Chappell, A., Ciais, P., Hauglustaine, D., Peñuelas, J., and Tao, S.: Sources, transport and deposition of iron in the global atmosphere, Atmos. Chem. Phys. Discuss., 15, 7645-7705, doi:10.5194/acpd-15-7645-2015, 2015.

Abstract: http://www.atmos-chem-phys-discuss.net/15/7645/2015/acpd-15-7645-2015.html

PDF full study: 

http://www.atmos-chem-phys-discuss.net/15/7645/2015/acpd-15-7645-2015.pdf

Edited May 3, 2015
notwhistanding

Updates:

 September 10, 2015 (2)
(This may be related to the anthropogenic bioavailable iron from combustion)
 Southern Ocean carbon sink bounces back with renewed vigour, study says
Sep 2015, 19:00 by Robert McSweeney - The Carbon Brief http://www.carbonbrief.org/blog/2015/09/southern-ocean-carbon-sink-bounces-back-with-renewed-vigour/


Delivery of anthropogenic bioavailable iron from mineral dust and combustion aerosols to the ocean

A. Ito1 and Z. Shi2 2015 (doi:10.5194/acpd-15-23051-2015)

http://www.atmos-chem-phys-discuss.net/15/23051/2015/acpd-15-23051-2015.pdf
 

July 22, 2015
Natural aerosols explain seasonal and spatial patterns of Southern Ocean cloud albedo
Science Advances 17 Jul 2015: Vol. 1, no. 6, e1500157 DOI: 10.1126/sciadv.1500157
http://advances.sciencemag.org/content/1/6/e1500157

June 16, 2015

Framing an ethics of climate management for the anthropocene

Christopher J. Preston -Date: 26 Jun 2014 - DOI 10.1007/s10584-014-1182-4

http://link.springer.com/article/10.1007/s10584-014-1182-4?utm_content=buffer9f368&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

La geoingeniería, la desesperación y los extremos políticos: falsas opciones y el negacionismo climático.

¡No! Los extremos políticos ya sea desde la izquierda es decir, del socialismo, etc., o de la derecha es decir los partidos como el T-Party de USA etc. no presentan alternativas viables a la geoingeniería.

De hecho, parecen ser lados opuestos de la misma moneda ideológica.

Al oponerse a la investigación en geoingeniería que podría arrojar luz sobre los efectos de las emisiones de aerosoles de combustibles fósiles, la extrema izquierda perpetúa la ignorancia que proporciona una cubierta a los mismos combustibles fósiles que dicen repugnar. Otra dinámica de la supuesta oposición a la geoingeniería por la extrema izquierda es lo aborrecible que son sus filosofías subyacentes, hasta el punto de casi hacer la perspectiva desagradable de la geoingeniería tolerable.

     

La extrema derecha hace más o menos lo mismo con su negacionismo del cambio climático antropogénico, incluso oponiéndose a los esfuerzos científicos que arrojarían luz sobre el asunto, ayudando a las industrias contaminantes a evitar enfrentar sus responsabilidades, y en el proceso muestran una filosofía de "egoísmo irracional" destructiva incluso a su propias poblaciones.

Otros, tal vez sintiéndose impotentes, al contemplar esta danza ejecutada a la perfección, quedan cruzados de brazos en desesperación. Esta tampoco es la respuesta, y de hecho puede complementar la inacción sintetizada por la dialéctica de la izquierda-derecha extrema.

Entonces… ¿cuál es la respuesta?

La apertura, la vulnerabilidad y la responsabilidad... ¿?

No lo sé.

Pero creo que el conocimiento, el conocimiento científico y el debate autentico, abierto; basado en hechos, sin histeria, podrían ponernos en el camino para encontrar las respuestas correctas.

Aquí los dejo con un video ficticio muy interesante (aunque esté en inglés) fundado por la Universidad de Bergen y el “The 7th Framework Programme”.

El video trae esta nota:
Exclusión de responsabilidad: El siguiente video es una obra de ficción. Se recomienda a los lectores que no debe confundirse con incidentes de la vida real.

Es parte de un sitio web por Paula Curvelo como un proyecto de su tesis doctoral.

Titulado: The Geoengineering  Debate Website.

"Lanzada en diciembre de 2012 y fue diseñada para promover un espacio de reflexión y debate sobre las implicaciones sociales y éticas de la geoingeniería".

Enlace:

https://sites.google.com/site/geoengineeringdebate/home

Sobre el autor de la página.

Paula Curvelo es estudiante de doctorado en filosofía ambiental en la Universidad de Lisboa, Portugal.

Obtuvo una licenciatura en Geografía (Universidad de Lisboa, UL), un diploma de postgrado en Sociología Urbana (Instituto Universitario de Lisboa, ISCTE-IUL), y una maestría en Sistemas de Información Geográfica y Ciencia (Universidad Nueva de Lisboa - ISEGI- NOVA).

Sus intereses de investigación incluyen los aspectos éticos, legales y sociales de la geoingeniería, la gobernanza de las tecnologías emergentes, la política del riesgo y la incertidumbre, y la filosofía de la tecnología.

Artículos de Paula sobre geoingeniería

Sueños de la ciencia de la geoingeniería - El fin del sueño cartesiano. 

Curvelo, Paula (2015) Geoengineering dreams in Science, Philosophy and Sustainability - The End of the Cartesian dream. Edited by Ângela Guimarães Pereira and Silvio Funtowicz. Routledge, pp. 114-131

Imag [en][inando] La geoingeniería - lo verosímil y lo inverosímil

Curvelo, Paula (2013) Imag[in]ing geoengineering – the plausible and the implausible, Int. J. Foresight and Innovation Policy, Vol. 9, Nos. 2/3/4, pp.162–187.         

Hacia un marco analítico para la evaluación de las dimensiones éticas de las propuestas de geoingeniería.

Curvelo, Paula (2013) Towards an Analytical Framework for Evaluating the Ethical Dimensions of Geoengineering Proposals. The International Journal of Climate Change: Impacts and Responses, volume 4, Issue 4, pp. 191-208.

          

Geoingeniería: reflexiones sobre los debates actuales.

Curvelo, Paula and Pereira, Ângela G. (2013) Geoengineering: reflections on current debates. The International Journal of Science in Society, Volume 4, Issue 3, pp. 1-21.

Cuestionando la visión mundial de la ciencia de geoingeniería.

Curvelo, Paula (2013) Questioning the Geoengineering Scientific Worldview. The International Journal of Interdisciplinary Environmental Studies no. 7 (1):35-53.

Explorando la Ética de la geoingeniería a través de imágenes.

Curvelo, Paula (2012) - Exploring the Ethics of Geoengineering through Images. The International Journal of The Image, Volume 2, Issue 2, pp.177-198.

Última actualización
Julio 28, 2016

Geoengineering, despair and the political extremes: false choices and deniability.

Last updated July 2, 2015

No! Political extremes be it from the left i.e. socialism etc. or the right i.e. T parties etc. do not present viable alternatives to geoengineering.

In fact they seem to be opposite sides of the same ideological coin. 

By opposing research into geoengineering, which could shed light into the effects of fossil fuel aerosols emissions, the extreme left perpetuates the ignorance providing cover for the same fossil fuels they claim to loath.  Another dynamic of the purported opposition to geoengineering by the extreme left is how abhorrent their underlying philosophies are, to the point of almost making the unpalatable prospect of geoengineering sufferable. 

     

The extreme right does pretty much the same with its deniability of anthropogenic climate change, even opposing scientific endeavors that would shed light on the matter, helping the polluting industries avoid responsibilities, and in the process displaying a philosophical ‘irrational egoism’ destructive even to their own populations.

Others, perhaps feeling helpless, witnessing this well-rehearsed dance, are throwing up their hands in despair.  This is also not the answer, and may in fact complement the inaction synthetized by the extreme left-right dialectic.

So what is the answer?

Openness, vulnerability and accountability…?

I do not know.

But I think that knowledge, scientific knowledge, and open genuine debate based on facts, without hysterics, could put us on the path to finding the right answers.

Here I leave your with an interesting fictional video by the University of Bergen and The 7th Framework Programme. 

It is part of a website by Paula Curvelo as a PhD project titled The Geoengineering  Debate Website.

"Launched in December 2012 and was designed to promote a space for reflection and debate on the social and ethical implications of geoengineering".

Link to The Geoengineering  Debate Website

https://sites.google.com/site/geoengineeringdebate/home

About the author of the page.

Paula Curvelo is a PhD candidate in environmental philosophy at the University of Lisbon, Portugal.

She holds a bachelor’s degree in Geography (University of Lisbon, UL), a postgraduate diploma in Urban Sociology (Instituto Universitário de Lisboa, ISCTE-IUL), and a MSc degree in Geographic Information Systems and Science (New University of Lisbon - ISEGI-NOVA).

Her current research interests include the ethical, legal and social aspects of geoengineering, the governance of emerging technologies, the politics of risk and uncertainty, and the philosophy of technology.

Paula's articles on Geoengineering

Curvelo, Paula (2015)  Geoengineering dreams in Science, Philosophy and Sustainability - The End of the Cartesian dream. Edited by Ângela Guimarães Pereira and Silvio Funtowicz. Routledge, pp. 114-131

               

Curvelo, Paula (2013) Imag[in]ing geoengineering – the plausible and the implausible, Int. J. Foresight and Innovation Policy, Vol. 9, Nos. 2/3/4, pp.162–187.

               

Curvelo, Paula (2013) Towards an Analytical Framework for Evaluating the Ethical Dimensions of Geoengineering Proposals. The International Journal of Climate Change: Impacts and Responses, volume 4, Issue 4, pp. 191-208

               

Curvelo, Paula and Pereira, Ângela G. (2013) Geoengineering: reflections on current debates. The International Journal of Science in Society, Volume 4, Issue 3, pp. 1-21.

Curvelo, Paula (2013) Questioning the Geoengineering Scientific Worldview. The International Journal of Interdisciplinary Environmental Studies no. 7 (1):35-53.

               

Curvelo, Paula (2012) - Exploring the Ethics of Geoengineering through Images. The International Journal of The Image, Volume 2, Issue 2, pp.177-198.


Update July 2, 2015

Interesting article:

STRANGE BEDFELLOWS: CLIMATE ENGINEERING POLITICS IN THE UNITED STATES (OPINION ARTICLE)

Nicholson and Thompson (2015) April 21, 2015 - for GEOENGINEERING OUR CLIMATE?
A Working Paper Series on the Ethics, Politics and Governance of Climate Engineering

http://geoengineeringourclimate.com/2015/04/21/strange-bedfellows-climate-engineering-politics-in-the-united-states-opinion-article/

Los Aerosoles Antropogénicos, el Cambio Climático y la Geoingeniería

Por Oscar A. Escobar
GT - FL USA

Actualizado Julio 1, 2015

“Los aerosoles son partículas diminutas suspendidas en la atmósfera.”

La definición de la Real Academia Española RAE:

Aerosol: 

1. m. Suspensión de partículas ultramicroscópicas de sólidos o líquidos en el aire u otro gas.

2. m. Sistema coloidal obtenido por dispersión de sustancias sólidas o líquidas en el seno de un gas.

Los aerosoles de azufre en la estratosfera son los más controversiales de los que popularmente se habla en debates sobre la gestión de la radiación solar o geoingeniería solar.

Mis comentarios a continuación de un breve artículo de la NASA acerca de lo que son los aerosoles.

(Las negritas son mi énfasis)

 Los aerosoles atmosféricos:

¿Qué son y por qué son tan importantes? Los aerosoles son partículas diminutas suspendidas en la atmósfera. Cuando estas partículas son lo suficientemente grandes, nos damos cuenta de su presencia, ya que dispersan y absorben la luz del sol. 

Su dispersión de la luz del sol puede reducir la visibilidad (niebla) y enrojecer los amaneceres y las puestas del sol. Los aerosoles interactúan directa e indirectamente con el presupuesto de radiación de la Tierra y el clima. 

Como efecto directo, los aerosoles dispersan la luz solar directamente hacia el espacio. 

Como efecto indirecto, aerosoles en la atmósfera inferior puede modificar el tamaño de las partículas de las nubes, cambiando la forma en que las nubes reflejan y absorben la luz solar, lo que afecta el balance de energía de la Tierra. 

Los aerosoles también puede actuar como sitios para que las reacciones químicas tengan lugar (la química heterogénea). Las más importantes de estas reacciones son las que conducen a la destrucción del ozono estratosférico. 

Durante el invierno en las regiones polares, los aerosoles crecen para formar nubes estratosféricas polares. Las grandes áreas superficiales de estas partículas de la nube proporcionan sitios para que reacciones químicas tengan lugar. 

Estas reacciones conducen a la formación de grandes cantidades de cloro reactivo y, en última instancia, a la destrucción de la capa de ozono en la estratosfera. 

Ahora existe evidencia mostrando que cambios similares en las concentraciones de ozono estratosférico se producen después de grandes erupciones volcánicas, como la del Monte Pinatubo en 1991, donde toneladas de aerosoles volcánicos fueron expulsadas hacia la atmósfera (Fig. 1).

Fig. 1 La dispersión de aerosoles volcánicos tiene un efecto drástico en la atmósfera de la Tierra. A raíz de una erupción, grandes cantidades de dióxido de azufre (SO2), ácido clorhídrico (HCL) y cenizas son arrojados en la estratosfera de la Tierra. El ácido clorhídrico, en la mayoría de los casos, se condensa con el vapor de agua y es removido con la lluvia fuera de la formación de la nube volcánica. El dióxido de azufre de la nube se transforma en ácido sulfúrico (H2SO4). El ácido sulfúrico se condensa rápidamente, produciendo partículas de aerosol que permanecen en la atmósfera durante largos períodos de tiempo. La interacción de los productos químicos sobre la superficie de los aerosoles, conocidos como la química heterogénea, y la tendencia de aerosoles para aumentar los niveles de cloro que puede reaccionar con nitrógeno en la estratosfera, es un contribuyente principal para la destrucción del ozono estratosférico”.

NASA FS-08.11.1996-LaRC - agosto 1996

Ahora sobre...

Los Aerosoles Antropogénicos, el Cambio Climático y la Geoingeniería

Los científicos generalmente evitan hacer la comparación entre las emisiones de dióxido de azufre (SO2)  de los volcanes y las fuentes antropogénicas. Después de hacerle una pregunta que surgió  a raíz de uno de sus artículos en Yale Climate Connections,  el periodista científico David Appell, me señaló que al comparar las emisiones de SO2 actuales entre las fuentes antropogénicas y las de las erupciones volcánicas... "la cuestión no es tanto sobre comparar eso a las de los volcanes, sino de cuánto llega a la estratosfera”.

Creo que el punto de David Appell es muy importante, sobre todo en lo que respecta a cuanto permanecen los aerosoles en la atmósfera (estos permanecen por más tiempo en la estratosfera que en la troposfera), que tan lejos viajan y varias otras razones tales como las interacciones químicas. Pero, para mí como profano (o como persona sin adiestramiento científico), hacer ese tipo de comparaciones y pensar en términos más concretos me ayuda a entender la jerga científica y los conceptos que describe.

Por ejemplo, tome las siguientes cifras anuales de emisiones mundiales de dióxido de azufre de origen antropogénico:

Más de 100 Tg / año (100.000 Gg / año) de SO2 antropogénico (dióxido de azufre) [1] [2]

Otro aerosol importante y potente pero con propiedades diferentes es el  Negro de Carbón (BC por sus siglas en inglés) con más de 9,1 Tg / año [3] [4]

Esas son grandes cantidades, pero para algunos de nosotros, profanos, se necesita un marco de referencia para comprender esa magnitud. Así que una cuidadosa comparación entre las emisiones antropogénicas y las volcánicas es útil:

La erupción del Monte Pinatubo de 1991 inyectó sobre 20 Tg de SO2 a la atmósfera [5] con algunos pensando que la mitad (10Tg) entró en la estratosfera sobre el trascurso de unos días. [6]

La cataclísmica erupción de 1991 del Monte Pinatubo en Las Filipinas, fue la segunda mayor erupción volcánica del siglo 20. [6a]

Además:

Desde el año 2000 se han producido una serie de erupciones volcánicas ‘modestas’, las tres más importantes en 2008, 2009, 2011, cada una de las cuales expulsó entre 1 Tg a 1,5 Tg de dióxido de azufre. [6]

Las emisiones volcánicas de SO2 anuales varían entre 1,5 a 50 Tg. [7]

Ahora sí entiendo mejor.

La inyección de SO2 del Monte Pinatubo a la atmósfera durante la erupción de 1991 fue extraordinaria... independientemente de lo mucho que realmente entró en la  estratosfera.

Pero aún más extraordinario es el hecho de que ‘nosotros’ actualmente estamos emitiendo a la atmósfera 5 veces el monto de la erupción del Monte Pinatubo en 1991, o el dióxido de azufre equivalente de hasta 100 'erupciones modestas’  ¡cada año! O sea más de 100 Tg anuales de SO2.

Con la marina mercante internacional por si sola emitiendo, para el año 2005, más del 12 Tg / año. [1]

Ahora volviendo a 'donde' en la atmósfera llega el SO2, y cómo puede afectar el clima...

"Los aerosoles tienen muy aproximadamente la misma capacidad de dispersar la luz solar de vuelta al espacio, dondequiera que se encuentren en la atmósfera." [8] Esta habilidad es contrarrestada cuando actúan para formar núcleos para formar nubes cirros altas, las que actúan para atrapar, y reflejar, la radiación saliente de onda larga de vuelta a la tierra; [9] y cuando o si actúan para formar nubes bajas y delgadas sobre la capa de hielo de Groenlandia las que pueden acelerar el derretimiento del hielo. [9a]

Pero sí, los aerosoles en la estratosfera se quedan allí por más tiempo -- un año o más [10] mientras que los que están más bajos en la troposfera tienden a permanecer allí sólo por una o dos semanas, [11], todo dependiendo de varios factores. Estos son tiempos cortos de "residencia" comparados con el dióxido de carbono, que puede permanecer en la atmósfera durante siglos, y es la razón por la cual el dióxido de azufre se clasifica como forzador/forzante climático de poca duración.

El consenso científico es que los aerosoles estratosféricos como el SO2 de las erupciones de volcanes enfrían el clima global. Err... excepto cuando una gran erupción volcánica causa ¡calentamiento de invierno! [12] [13]

Aunque en ocasiones he repetido aquí en este blog el mantra de que "los aerosoles de azufre enfrían el clima", un concepto más preciso es que han enmascarado el calentamiento global en algunas regiones.

A través del tiempo han habido varios estudios contradictorios e informes que apuntan a los aerosoles antropogénicos de azufre como principales, o una causa importante de lo que se ha llamado... "la pausa o ralentización en el calentamiento global o hiato." [14] [15] mientras que otros sostienen que pequeñas erupciones volcánicas recientes pueden ser la fuente principal de aerosoles y por lo tanto responsables de la pausa, [16] [17] con todavía algunos otros teorizando que se debe a otros factores como los ciclos de "variabilidad natural" y la absorción de calor por los océanos. [18] [19]

Pero...

En su mayor parte, las consideraciones ambientales, sociales, jurídicas, económicas, éticas y políticas de los efectos de 100 Tg / año  de emisiones antropogénicas, o sea el equivalente anual a más de 5 veces las emisiones de SO2 a la atmósfera por la erupción del Pinatubo, está ausente en los debates sobre la geoingeniería del clima.

Con algunos desechando tajantemente estas preocupaciones.

Tal vez la excepción más reciente que conozco entre los opositores a la geoingeniería climática es Clive Hamilton que escribe brevemente sobre los efectos de los aerosoles antropogénicos de SO2 en su libro Amos de la Tierra - El amanecer de la Era de la Ingeniería Climática. 2013 (Capítulo 3. p70-71 edición rústica). (Se puede ver el extracto de Amos de la Tierra en este blog, fecha Marzo 16, 2015)

Aunque como ya he dicho antes, este tema de los aerosoles troposféricos está en gran medida ausente en las discusiones de geoingeniería, recibe atención de pasada solamente, y quizás tangencialmente. Por ejemplo cuando los estudios e informes hablan de un posible aumento en las temperaturas globales en el 2020 o 2025, [20], que es casualmente el marco de tiempo dado para que entren en vigencia algunas leyes de control de la contaminación por SO2. [21] Además, el año 2020 ha sido citado como una fecha de inicio para las actividades de geoingeniería solar (SRM por sus siglas en inglés). [8]

Creo que no discutir los aerosoles troposféricos es una omisión flagrante de las comunidades ambientales y políticas, así como de otras más. Especialmente a la luz de los informes de la acelerada acidificación de los océanos, [22] y teniendo en cuenta el papel que la marina mercante internacional puede estar jugando en esta aceleración con sus 12 Tg / año de azufre acidificante y emisiones de CO2. El acelerado deshielo Ártico con pérdidas record, [23], teniendo en cuenta el papel del negro de carbón sobre el hielo y de otros factores que atrapan radiación térmica. [9] Los múltiples informes globales sobre las sequías persistentes y que también están rompiendo récords; [24] [25] [26] y otros factores ambientales tales como los efectos sobre la biodiversidad, la acidificación de los océanos y la salud.

Todos estos y otros eventos ambientales a nivel global que son atribuidos (con razón, en mi opinión) al dióxido de carbono y otras formas de contaminación, tienen también una correlación muy fuerte a los aerosoles de azufre, y mientras que la correlación no implica causalidad, en mi opinión, ciertamente hacen una llamada para la investigación exhaustiva y pronta dentro de un marco de geoingeniería.

¿Por qué es importante que los aerosoles antropogénicos sean investigados dentro de un marco de geoingeniería?

1. Trauma por terminación (Termination Shock). Magnitud del aumento esperado en las temperaturas cuando se termine el forzamiento climático de los aerosoles troposféricos antropogénicos [27] [28].

 ¿Estamos a tiempo de evitarlo o ya estamos encerrados en el trauma por terminación?

2. Encierre Socio-técnico (Lock-in). Tanto el acelerar la Gestión de la Radiación Solar y / o mantener las emisiones actuales de SO2, son formas de ‘atrapamiento o encierre socio-técnico’. [29]

 ¿Cómo evitarlo?

3. Riesgo moral. "El riesgo moral nos informa de cómo los individuos asumen en sus decisiones mayores riesgos cuando las posibles consecuencias negativas de sus actos no son asumidas por ellos, sino por un tercero."

¿Son los hechos sobre los aerosoles antropogénicos hechos importantes?

¿Quién se beneficia de la ignorancia?

Los subsidios a lo combustibles fósiles, [30] [31] [32] la exploración de petróleo en el Ártico, [33] las nuevas rutas marítimas en el Ártico, [34] [35] la minería en el Ártico, [36], la militarización del Ártico, [37] [38], etc. ¿Acaso no son estas expresiones de riesgo moral en curso? [39]

¿Quién se beneficia? ¿Quién está pagando el precio?

¿Hasta la fecha ha sido el debate o la falta de debate un ejercicio de dialéctica hegeliana con un resultado prescrito?

¿Vamos a seguir por este camino?

Actualización Julio 1, 2015
Unas gráficas muy interesantes que extraídas de un articulo de Bloomberg basado en información de la NASA. Arriba, un poco de calentamiento por el CO2 emitido por los volcanes. Abajo, el efecto de enfriamiento producido por los aerosoles de origen humano producto de la combustión para energía.

La parte buena, vamos a decir, es el enfriamiento producido por estos aerosoles. La parte mala va mas allá de 'lluvia ácida" como lo que indica el articulo. También hay grandes efectos negativos en la salud y otros ecológicos, como en los ecosistemas y diversidad biológica de gran alcance.  

What’s Really Warming the World?

By Roston/Migliozzi - June 24, 2015 - Bloomberg

http://www.bloomberg.com/graphics/2015-whats-warming-the-world/

 Referencias

 [1] Anthropogenic sulfur dioxide emissions: 1850–2005

http://www.atmos-chem-phys.net/11/1101/2011/acp-11-1101-2011.pdf

[2] The last decade of global anthropogenic sulfur dioxide: 2000–2011 emissions

http://iopscience.iop.org/1748-9326/8/1/014003/article

[3] Trend in Global Black Carbon Emissions from 1960 to 2007

Rong Wang et al

Environ. Sci. Technol., 2014, 48 (12), pp 6780–6787

DOI: 10.1021/es5021422

Publication Date (Web): May 13, 2014

http://pubs.acs.org/doi/abs/10.1021/es5021422

[4] Study estimates global black carbon emissions up 72% from 1960-2007; BC emissions intensity down 52%

Green Car Congress - 31 May 2014

http://www.greencarcongress.com/2014/05/20140531-bc.html

[5] Global tracking of the SO2 clouds from the June, 1991 Mount Pinatubo eruptions

Gregg J. S. Bluth

Article first published online: 7 DEC 2012

DOI: 10.1029/91GL02792

http://onlinelibrary.wiley.com/doi/10.1029/91GL02792/abstract

[6] An overview of geoengineering of climate using stratospheric sulfate aerosols

Philip J Rasch et al

The Royal Society – Philosophical Transactions A

DOI: 10.1098/rsta.2008.0131 Published 13 November 2008

http://rsta.royalsocietypublishing.org/content/366/1882/4007

“For example, the eruption of Mount Pinatubo is believed to have injected approximately 10 Tg S (in the form of SO2) over a few days”

[6a] The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines

USGS - U.S. Geological Survey Fact Sheet 113-97

http://pubs.usgs.gov/fs/1997/fs113-97/

[7] Emissions from volcanoes

Christiane Textor, Hans-F. Graf, Claudia Timmreck, Alan Robock

Emissions of Atmospheric Trace Compounds

Advances in Global Change Research Volume 18, 2004, pp 269-303

http://link.springer.com/chapter/10.1007/978-1-4020-2167-1_7

[8] A Case for Climate Engineering

David Keith (2014)

https://books.google.com/books?id=JXf6AAAAQBAJ&printsec=frontcover&dq=A+Case+for+Climate+Engineering++By+David+Keith&hl=en&sa=X&ei=GmEQVcOpPISWgwTz1IGAAg&ved=0CCcQ6AEwAA#v=onepage&q=A%20Case%20for%20Climate%20Engineering%20%20By%20David%20Keith&f=false

[9] Possible influence of anthropogenic aerosols on cirrus clouds and anthropogenic forcing

J. E. Penner – Feb 3, 2009

Atmos. Chem. Phys., 9, 879-896, 2009

www.atmos-chem-phys.net/9/879/2009/

doi:10.5194/acp-9-879-2009

http://www.atmos-chem-phys.net/9/879/2009/acp-9-879-2009.html

[9a] Thin, Low Arctic Clouds Played an Important Role in Widespread 2012 Greenland Ice Sheet Melt

National Science Foundation - Press Release 13-060 - April 3, 2013

http://www.nsf.gov/news/news_summ.jsp?cntn_id=127438

[10] Does air pollution—specifically particulate matter (aerosols)—affect global warming?

Summary prepared by M. Baker (University of Washington) and reviewed by B. Ekwurzel, N. Cole, P. Frumhoff, and S. Shaw (UCS).

Union of Concerned Scientists 

http://www.ucsusa.org/global_warming/science_and_impacts/science/aerosols-and-global-warming-faq.html#.VPpy5PnF8co 

http://www.bolin.su.se/index.php/past-workshops/274-workshop-high-latitude-volcanic-eruptions-and-climate-filling-the-gaps-5-6-november-2014

[11] Estimates of residence times of sulfate aerosols in ambient air

E.A. Bondietti∗, C. Papastefanou∗∗

Science of The Total Environment

Volume 136, Issues 1–2, 15 August 1993, Pages 25–31

doi:10.1016/0048-9697(93)90294-G

http://www.sciencedirect.com/science/article/pii/004896979390294G

[12] Winter warming from large volcanic eruptions

Alan Robock and Jianping Mao - 7 DEC 2012

DOI: 10.1029/92GL02627

http://onlinelibrary.wiley.com/doi/10.1029/92GL02627/abstract

[13] Workshop “High-latitude volcanic eruptions and climate: filling the gaps”, 5–6 November 2014

Bolin Center for Climate Research

http://www.bolin.su.se/index.php/past-workshops/274-workshop-high-latitude-volcanic-eruptions-and-climate-filling-the-gaps-5-6-november-2014

[14] New study blames 10-year lull in global warming on China coal use, air pollution

By Andrew Freedman – Capital Weather Gang – WP – 07/05/2011

http://www.washingtonpost.com/blogs/capital-weather-gang/post/new-study-blames-10-year-lull-in-global-warming-on-china-coal-use-air-pollution/2011/07/05/gHQAwjV8yH_blog.html

[15] Global is the new local: Pollution changes clouds, climate downstream

By Carol Rasmussen, - NASA's Earth Science News Team - January 26, 2015

http://climate.nasa.gov/news/2218/

[16] Volcanic aerosols, not pollutants, tamped down recent Earth warming, says CU study

March 1, 2013 - Natural Sciences, Environment, Institutes, Cooperative Institute for Research in Environmental Science (CIRES)

http://www.colorado.edu/news/releases/2013/03/01/volcanic-aerosols-not-pollutants-tamped-down-recent-earth-warming-says-cu#sthash.PmHnyQE0.dpuf

[17] Volcanic contribution to decadal changes in tropospheric temperature

Published online 23 February 2014

Benjamin D. Santer et al - Nature Geoscience 7, 185–189 (2014) doi:10.1038/ngeo2098

http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2098.html

[18] Cool Pacific Ocean Slowed Global Warming

By Becky Oskin – Live Science - February 26, 2015

http://www.livescience.com/49967-pacific-ocean-global-warming-pause.html

[19] Cause of global warming hiatus found deep in the Atlantic Ocean 

Phys.Org – Aug 21, 2014

http://phys.org/news/2014-08-global-hiatus-deep-atlantic-ocean.html

[20] Global warming likely to accelerate after “pause”, say scientists

By Sophie Yeo – RTCC - Last updated on 24 February 2015

http://www.rtcc.org/2015/02/24/global-warming-likely-to-accelerate-after-pause-say-scientists/#sthash.YIIK6oGM.dpuf

[21] Sulphur oxides (SOx) – Regulation 14

IMO International Maritime Organization

http://www.imo.org/OurWork/Environment/PollutionPrevention/AirPollution/Pages/Sulphur-oxides-%28SOx%29-%E2%80%93-Regulation-14.aspx

[22] Ocean Acidification

Summary for Policymakers

Third Symposium on the Ocean in a High-CO2 World

The International Geosphere-Biosphere Programme (IGBP)

http://www.igbp.net/download/18.30566fc6142425d6c91140a/1385975160621/OA_spm2-FULL-lorez.pdf

[23] Arctic sea ice winter maximum may be record low

Yereth Rosen - Alaska Dispatch News - March 9, 2015

https://www.adn.com/article/20150309/arctic-sea-ice-winter-maximum-may-be-record-low

[24] U.S. Drought Monitor

http://droughtmonitor.unl.edu/

[25] Little relief in Central America's food crisis

By Claire Luke - 19 February 2015

https://www.devex.com/news/little-relief-in-central-america-s-food-crisis-85387

[26] Taps Start to Run Dry in Brazil’s Largest City

By SIMON ROMEROFEB. 16, 2015

http://www.nytimes.com/2015/02/17/world/americas/drought-pushes-sao-paulo-brazil-toward-water-crisis.html?_r=0

[27] A new Geoengineering Model Intercomparison Project (GeoMIP) experiment designed for climate and chemistry models

S. Tilmes et al.

Geosci. Model Dev., 8, 43–49, 2015

www.geosci-model-dev.net/8/43/2015/

doi:10.5194/gmd-8-43-2015

[28] 4. Post-Implementation Stage - Termination Problem

Ethics of Geoengineering Online Resource Center

University of Montana

http://www.umt.edu/ethics/resourcecenter/why_ethics/post_implementation.php

[29] Geoingeniería: cuestiones de dependencia de la trayectoria (path-dependence) y encierre socio-técnico (lock-in) (Traducción)

Rose Cairns (SPRU – Estudios de Políticas de la Ciencia y la Tecnología)

 https://www.academia.edu/8480009/Geoingenier%C3%ADa_cuestiones_de_dependencia_de_la_trayectoria_path-dependence_y_encierre_socio-t%C3%A9cnico_lock-in_Traducci%C3%B3n_

http://geoengineeringclimateissues.blogspot.com/2014/09/geoingenieria-cuestiones-de-dependencia.html 

Geoengineering: issues of path-dependence and socio-technical lock-in

Rose Cairns (SPRU – Science and Technology Policy Research)

October 2013

http://geoengineering-governance-research.org/perch/resources/background-briefing.pdf

Wires Climate Change - Advanced Review

Published Online: Jun 27 2014

DOI: 10.1002/wcc.296

http://wires.wiley.com/WileyCDA/WiresArticle/wisId-WCC296.html

[30] Fossil Fuel Subsidies Are Twelve Times Renewables Support

by Bloomberg News - July 29, 2010

http://www.bloomberg.com/news/articles/2010-07-29/fossil-fuel-subsidies-are-12-times-support-for-renewables-study-shows

[31] Energy subsidies aren’t just for renewables, fossil fuels get the lion’s share

By The BDN Editorial Board,

Posted Feb. 19, 2015

 http://www.worldfinance.com/home/fossil-fuels-arent-going-anywhere

[32] Fossil fuel clampdown could finally be on its way

By Matt TimmsThursday, World Finance - February 26th, 2015

http://www.worldfinance.com/home/fossil-fuels-arent-going-anywhere

[33] Shell oil drilling in Arctic set to get US government permission

By Terry Macalister – The Guardian – March 22, 2015

http://www.theguardian.com/business/2015/mar/22/shell-oil-driling-in-arctic-set-to-get-us-government-permission

[34] The Melting Arctic: A Fragile Frontier of Riches and Risk Opens for Business

By Sabrina Shankman, InsideClimate News - Mar 17, 2015

http://insideclimatenews.org/news/17032015/melting-arctic-fragile-frontier-riches-and-risk-opens-business

[35] China Can Play Key Role in Arctic Shipping

By MarEx 2015-03-21

http://www.maritime-executive.com/features/china-can-play-key-role-in-arctic

[36] Future Arctic: More Mining, More Shipping and More Tourists

By Benjamin Hulac and ClimateWire - March 13, 2015

http://www.scientificamerican.com/article/future-arctic-more-mining-more-shipping-and-more-tourists/

[37] Could the Arctic be the next Crimea?

BY Duncan Depledge - Postdoctoral researcher, Royal Holloway

Quartz – March 23, 2015

http://qz.com/368022/could-the-arctic-be-the-next-crimea/

[38] Russia's Arctic pivot is a massive military undertaking

JEREMY BENDER – Business Insider - MAR. 12, 2015

http://www.businessinsider.com/russias-arctic-pivot-is-a-massive-military-undertaking-2015-3

[39] Riesgo Moral

Wikipedia la enciclopedia libre

http://es.wikipedia.org/wiki/Riesgo_moral

Moral Hazard: “In economics, moral hazard occurs when one person takes more risks because someone else bears the burden of those risks. A moral hazard may occur where the actions of one party may change to the detriment of another after a financial transaction has taken place.

Moral hazard occurs under a type of information asymmetry where the risk-taking party to a transaction knows more about its intentions than the party paying the consequences of the risk. More broadly, moral hazard occurs when the party with more information about its actions or intentions has a tendency or incentive to behave inappropriately from the perspective of the party with less information.”

Moral Hazard - From Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Moral_hazard

Otras lecturas:

Climate forcing growth rates: doubling down on our Faustian bargain

Environmental Research Letters Volume 8 Number 1

James Hansen et al 2013 Environ. Res. Lett. 8 011006 doi:10.1088/1748-9326/8/1/011006

http://iopscience.iop.org/1748-9326/8/1/011006

Top Lessons to be Learned from Warming ‘Hiatus’

David Appell  —  Yale Climate Connections --- March 5, 2015

http://www.yaleclimateconnections.org/2015/03/top-lessons-to-be-learned-from-warming-hiatus/#comment-1492782

Anthropogenic Aerosols, Climate Change and Geoengineering

By Oscar A. Escobar
GT - FL USA

Last Update January 14, 2016:

Newest -A23K-04: Evidence of Clear-Sky Daylight Whitening: Are we already conducting geoengineering?
Newest -[press review] Media responses to Charles Long on "Unintentional Geoengineering"
-SA article at bottom
-March 25 Event: Dimming the Sun: How Clouds and Air Pollution Affect Global Climate

-IPCC Fourth Assessment Report (AR4) - 3.4.4.2 Surface Radiation

-Further comments below the update.
-NASA - GLORY Mission video

Aerosols are minute particles suspended in the atmosphere.

Oxford definition: A colloidal suspension of particles dispersed in air or gas.

Sulfur aerosols in the stratosphere are the most controversial and popularly talked about in solar radiation management discussions. 

A short article from NASA about what aerosols are. My comments below the article.

(My emphasis)

 “Atmospheric Aerosols:

What Are They, and Why Are They So Important? Aerosols are minute particles suspended in the atmosphere. When these particles are sufficiently large, we notice their presence as they scatter and absorb sunlight. Their scattering of sunlight can reduce visibility (haze) and redden sunrises and sunsets. Aerosols interact both directly and indirectly with the Earth's radiation budget and climate. As a direct effect, the aerosols scatter sunlight directly back into space. As an indirect effect, aerosols in the lower atmosphere can modify the size of cloud particles, changing how the clouds reflect and absorb sunlight, thereby affecting the Earth's energy budget. Aerosols also can act as sites for chemical reactions to take place (heterogeneous chemistry). The most significant of these reactions are those that lead to the destruction of stratospheric ozone. During winter in the Polar Regions, aerosols grow to form polar stratospheric clouds. The large surface areas of these cloud particles provide sites for chemical reactions to take place. These reactions lead to the formation of large amounts of reactive chlorine and, ultimately, to the destruction of ozone in the stratosphere. Evidence now exists that shows similar changes in stratospheric ozone concentrations occur after major volcanic eruptions, like Mt. Pinatubo in 1991, where tons of volcanic aerosols are blown into the atmosphere (Fig. 1).

 

Fig. 1 The dispersal of volcanic aerosols has a drastic effect on the Earth's atmosphere. Following an eruption, large amounts of sulfurr dioxide (SO2), hydrochloric acid (HCL) and ash are spewed into the Earth's stratosphere. Hydrochloric acid, in most cases, condenses with water vapor and is rained out of the volcanic cloud formation. Sulfur dioxide from the cloud is transformed into sulfuric acid (H2SO4). The sulfuric acid quickly condenses, producing aerosol particles which linger in the atmosphere for long periods of time. The interaction of chemicals on the surface of aerosols, known as heterogeneous chemistry, and the tendency of aerosols to increase levels of chlorine which can react with nitrogen in the stratosphere, is a prime contributor to stratospheric ozone destruction.”

NASA FS-1996-08-11-LaRC - August 1996

So about... 

Anthropogenic Aerosols, Climate Change and Geoengineering

Scientists generally shy away from comparing sulfur dioxide (SO2) emission between volcanos and anthropogenic sources.  After asking a question prompted by one of his articles in Yale Climate Connections, science journalist David Appell, pointed out to me that in comparing current SO2 emissions between anthropogenic and volcanic eruptions sources… “the question isn't so much about comparing that to volcanoes, but of how much of that gets to the stratosphere”.

I think David Appell’s point is very important, particularly in respect to how long the aerosols stay in the atmosphere (they stay longer in the stratosphere than in the troposphere), how far away they travel and various other reasons such as chemical interactions.  But, for me as a layperson, making that type of comparisons and thinking in more concrete terms helps in understanding the scientific jargon and science concepts it describes.

Take the following figures of yearly global anthropogenic sulfur dioxide for example:

Over 100 Tg/yr (100,000 Gg/yr) of anthropogenic SO2 (Sulfur Dioxide) [1] [2]

Another important and potent aerosol but with differnt properties is Black Carbon (BC) with over 9.1 Tg/yr [3] [4]

Those are big quantities, but for some of us, lay people, a frame of reference is needed to comprehend that magnitude. So a careful comparison between anthropogenic and volcanic emissions is helpful:

The Mount Pinatubo Eruption of 1991 injected about 20Tg of SO2 into the atmosphere [5] with some thinking half of that (10Tg) went  into the stratosphere over the course of a few days. [6]

The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines was the second-largest volcanic eruption of the 20th century. [6a]

Furthermore:

Since 2000 there have been a number of modest volcanic eruptions, the three most significant in 2008, 2009, 2011, each of which expulsed between 1Tg to 1.5 Tg of Sulfur Dioxide. [6]
Yearly volcanic emissions vary between 1.5 to 50 Tg. [7]

Ok. So now I understand better.  

Mount Pinatubo’s injection of SO2 into the atmosphere during the 1991 eruption was extraordinary… regardless of how much actually went into the stratosphere.

But even more extraordinary is the fact that ‘we’ are currently emitting into the atmosphere over 5 times the amount of Mount Pinatubo’s eruption in 1991, or the equivalent of up to 100 or more ‘moderate eruptions’ worth of Sulfur Dioxide every year! With international shipping alone emitting, by 2005, over 12 Tg/yr. [1] 

Now going back to ‘where in the atmosphere’ the SO2 is going to, and how they may affect climate…

“Aerosols have very roughly the same ability to scatter sunlight back to space, wherever they are in the atmosphere.” [8] This ability is countered when they act to form nuclei for high cirrus clouds, which act to trap, and reflect, outgoing long wave radiation back to earth; [9] and when or if they act to form thin low laying clouds over Greenland’s ice sheet. [9a] 

But yes, aerosols in the stratosphere stay there longer-- a year or more [10] while those lower in the troposphere tend to stay there only for a week or two, [11], all depending on various factors. These are short ‘residence’ times when compared to carbon dioxide, which can stay in the atmosphere for centuries, and is the reason why sulfur dioxide is classified as a Short Lived Climate Forcer/Pollutant.

The scientific consensus is that stratospheric aerosols like SO2 from volcano eruptions cool the global climate. Err… except when large volcanic eruption cause “winter warmig!” [12] [13]

Although in occasions I have repeated here in this blog the mantra that “sulfur aerosols cool the climate” a more accurate concept is that they have masked global warming in some regions. 

Over time there have been various conflicting studies and reports pointing to anthropogenic sulfur aerosols as the main or a significant cause of what is being called... ‘the global warming pause or hiatus.’ [14][15] While others argue that recent small volcanic eruptions may be the main aerosol source and therefore responsible for the pause, [16] [17] with still some others theorizing it is due to various other factors like cycles of ‘natural variability’ and heat uptake by the oceans. [18] [19] 

But...

For the most part, the environmental, social, legal, economical, ethical and political considerations of the effects of 100 Tg/yr, or over 5 yearly Pinatubo’s worth of anthropogenic SO2 emissions into the atmosphere is largely absent on Climate Geoengineering discussions. 

With some actually dismissing these concerns out of hand.

Perhaps the most recent exception that I know of from opponents to deliberate climate geoengineering is Clive Hamilton Hamilton who briefly writes about anthropogenic SO2 aerosols in his book Earth Masters – The Dawn of the Age of Climate Engineering. 2013 (Chapter 3. p70-71 paperback).

Although as I said before, this topic of tropospheric aerosols is largely absent from the geoengineering discussions, it receives attention only in passing, and perhaps tangentially, for example when studies and reports speak of a possible spike in global temperatures by 2020 or 2025, [20] which is coincidentally the time frame given for some SO2 pollution control laws.[21] Also the year 2020 has been referenced as a start date for SRM geoengineering activities. [8]  

I think not discussing tropospheric aerosols is a glaring and concerning omission by the environmental and political communities, as well as others. Especially in light of reports of accelerated ocean acidification, [22] and taking into consideration the role that international shipping may be playing in this acceleration with its 12 Tg/yr of acidifying sulfur and CO2 emissions.  The accelerated and record Arctic ice loss, [23] taking in consideration the role of black carbon and other radiation trapping factors. [9] The multiple global reports on persistent and record breaking droughts; [24] [25] [26] and other environmental factors such as the effects on biodiversity, ocean acidification and health.

All these and other global environmental events that are (rightfully in my view) attributed to carbon dioxide and other forms of pollution, have also a very strong correlation to sulfur aerosols, and while correlation does not imply causation, in my view it certainly does call for exhaustive and prompt investigation within a geoengineering framework.

So why is it important that anthropogenic aerosols be investigated within a geoengineering framework?

1. Termination shock. Magnitude of expected raise in temperatures when climate forcing from the anthropogenic tropospheric aerosols is terminated [27] [28].  

 Are we in time to avoid it or are we already locked-in to termination shock?

2. Socio-technical lock-in. Both SRM ramp up and/or a continuation of business as usual SO2 emissions, are forms of socio-technical lock-in. [29]

How to avoid it?

3. Moral hazard. “Moral hazard occurs under a type of information asymmetry where the risk-taking party to a transaction knows more about its intentions than the party paying the consequences of the risk.” 

Are the facts about anthropogenic aerosols important facts? 

Who benefits from ignorance?

Fossil fuels subsidies, [30][31][32] Arctic oil exploration, [33] new Arctic shipping routes, [34] [35] Arctic mining, [36], Arctic militarization, [37][38] etc. Are they not expressions of ongoing moral hazard? [39]

Who benefits? Who is paying the price?

To date has the debate or lack thereof been an exercise in Hegelian dialectics with a prescribed outcome?

Will we continue down this path? 

Updates:

March 25, 2015 

I don't know if this event is a result of this blog, I found the event posting yesterday March 24.
(My emphasis)

Environmental and Urban Studies Program, Distinguished Scientist Lecture Series, and Bard Center for Environmental Policy present

Dimming the Sun:
How Clouds and Air Pollution Affect Global Climate [40]

Beate Liepert
Senior Research Scientist - Climate & Solar Energy
NorthWest Research Associates

Wednesday, March 25, 2015

While anthropogenic greenhouse gas emissions are well known contributors to global warming, the additional impact of short-lived air pollution (e.g. anthropogenic aerosols) is not well understood. The potential for this air pollution to modify climate or even mask global warming will be introduced and the wider implications of aerosol-induced global dimming, including geoengineering prospects, will be discussed.

Beate Liepert is scientist and artist. Climate change and specifically the cycling of water and energy in a changing world are overarching themes of her research. Highlights of her research are the discovery of the phenomenon “global dimming”, which is the increase in atmospheric transparency, and its responsibility for masking parts of the global warming signal in the 20th century. She further pioneered research on the causes of dimming and its implications for the water and carbon cycle on Earth. Beate received a PhD in Meteorology from the Ludwig Maximilians University in Munich, Germany.

In 1996 she moved to New York City to become Doherty Research Scientist at Columbia University. Beate contributed a section on global dimming to the IPCC 4th Assessment Report “Scientific Basis” (chapter 3.4.4.2) that won the Nobel Prize for Peace in 2007. While living in New York City, Beate attended the Certificate Program of Fine Arts at Parsons New School of Design. She moved to Seattle in 2009, and became partner and principal investigator at NorthWest Research Associates, a cooperative for basic and applied research.

Beate’s current research focuses on shifting weather patterns with global warming, and novel solar energy innovations. As artist Beate collaborates with the Seattle based artist, educator and designer Marisa Vitiello on a series of automatism drawings. In 2015 Marisa and Beate have been selected by Spaceworks Tacoma to do an installation in the downtown storefront program and in the Evergreen Association of Fine Arts Gallery Open Abstract Show in Seattle Washington.

Here is the IPCC (AR4) chapter referred to in the event posting from Bard College:

IPCC Fourth Assessment Report (AR4)                  

Climate Change 2007: The Physical Science Basis

Chapter 3 Observations: Surface and Atmospheric Climate Change [41]

3.4.4.2 Surface Radiation

(My emphasis)

The energy balance at the surface requires net radiative heating to be balanced by turbulent energy fluxes and thus determines the evolution of surface temperature and the cycling of water, which are key parameters of climate change (see Box 7.1). In recent years, several studies have focused on observational evidence of changing surface radiative heating.

Reliable SW radiative measurement networks have existed since the 1957–1958 International Geophysical Year.

A reduction in downward solar radiation (‘dimming’) of about 1.3% per decade or about 7 W m–2 was observed from 1961 to 1990 at land stations around the world (Gilgen et al., 1998; Liepert, 2002).

Additional studies also found declines in surface solar radiation in the Arctic and Antarctic (Stanhill and Cohen, 2001) as well as at sites in the former Soviet Union (Russak, 1990; Abakumova et al., 1996), round the Mediterranean Sea (Aksoy, 1997; Omran, 2000), China (Ren et al., 2005), the USA (Liepert, 2002) and southern Africa (Power and Mills, 2005). Stanhill and Cohen (2001) claim an overall globally averaged reduction of 2.7% per decade but used only 30 records.

However, the stations where these analyses took place are quite limited in domain and dominated by large urban areas, and the dimming is much less at rural sites (Alpert et al., 2005) or even missing altogether over remote areas, except for identifiable effects of volcanic eruptions, such as Mt. Pinatubo in 1991 (Schwartz, 2005).

At the majority of 421 analysed sites, the decline in surface solar radiation ended around 1990 and a recovery of about 6 W m–2 occurred afterwards (Wild et al., 2004; 2005).

The increase in surface solar radiation (‘brightening’) agrees with satellite and surface observations of reduced cloud cover (Wang et al., 2002b; Wielicki et al., 2002a; Rossow and Dueñas, 2004; Norris, 2005b; Pinker et al., 2005), although there is evidence that some of these changes are spurious (see Section 3.4.3).

In addition, the satellite-observed increase in surface radiation noted by Pinker et al. (2005) occured primarily over ocean, whereas the increase observed by Wild et al. (2005) was restricted to land stations.

From 1981 to 2003 over central Europe, Philipona and Dürr (2004) showed that decreases in surface solar radiation from increases in clouds were cancelled by opposite changes in LW radiation and that increases in net radiative flux were dominated by the clear-sky LW radiation component relating to an enhanced water vapour greenhouse effect.

Alpert et al. (2005) provided evidence that a significant component of the reductions may relate to increased urbanisation and anthropogenic aerosol concentrations over the period (see also Section 7.5).

This has been detected in solar radiation reductions for polluted regions (e.g., China; Luo et al., 2001), but cloudiness changes must also play a major role, as shown for European sites and the USA (Liepert, 2002; Dai et al., 2006).

In the USA increasing cloud optical thickness and a shift from cloud-free to more cloudy skies are the dominating factors compared to the aerosol direct effects. Possible causes of the 1990s reversal are reduced cloudiness and increased cloud-free atmospheric transparency due to the reduction of anthropogenic aerosol concentrations and recovery from the effects of the 1991 eruption of Mt. Pinatubo. See Box 3.2 for more discussion and a likely explanation of these aspects.

From Box 3.2: The Dimming of the Planet and Apparent Conflicts in Trends of Evaporation and Pan Evaporation

“increased clouds impose a greenhouse effect and reduce outgoing LW radiation (Philipona and Dürr, 2004), so that changes in net radiation can be quite small or even of reversed sign. Recent re-assessments suggest increasing trends of evapotranspiration over southern Russia during the last 40 years (Golubev et al., 2001) and over the USA during the past 40 or 50 years (Golubev et al., 2001; Walter et al., 2004) in spite of decreases in pan evaporation. Hence, in most, but not all, places the net result has been an increase in actual evaporation but a decrease in pan evaporation. Both are related to observed changes in atmospheric circulation and associated weather.”

OE:
According to David Appell, citing a more recent 2014 paper by Santer et al. (Volcanic contribution to decadal changes in tropospheric temperature doi:10.1038/ngeo2098 paywalled) stratospheric optical depth* has increased 4% - 7% per year from 2000 to 2009. If that is correct, that would make it... 

A total increase of 62% in the stratospheric optical depth in the 2000-2009 decade alone.


I will e mail Dr. Liepert to find out if there will be video recording of her discussion, and if this would be available for public viewing. Also I will include a copy of this post.

*"Optical depth measures the attenuation of the transmitted radiant power in a material. Attenuation can be caused by absorption, but also reflection, scattering, and other physical processes." [42] 

In other words how much light goes through. Higher optical depth means less light goes through.

NASA - GLORY - The Particle Puzzle

A public domain video by NASA Goddard

On 4 March 2011, the Aerosol Polarimetry Sensor (APS) was lost as a consequence of the failed launch of the Glory Mission. [43]

Video also on You Tube: https://www.youtube.com/watch?list=UUKuHdk7DqczMNVkgspQECng&v=eJkjpVjwS4k
and here: https://www.youtube.com/watch?v=gi1Dd5ztb9Y

Updates:



Newest: [press review] Media responses to Charles Long on "Unintentional Geoengineering"
http://www.climate-engineering.eu/single/items/press-review-media-responses-to-charles-long-on-unintentional-geoengineering.html

Newest: A23K-04: Evidence of Clear-Sky Daylight Whitening: Are we already conducting geoengineering?
https://agu.confex.com/agu/fm15/meetingapp.cgi/Paper/59257

July 22, 2015
Natural aerosols explain seasonal and spatial patterns of Southern Ocean cloud albedo
Science Advances 17 Jul 2015: Vol. 1, no. 6, e1500157 DOI: 10.1126/sciadv.1500157
http://advances.sciencemag.org/content/1/6/e1500157

July 2, 2015

How to Misinterpret Climate Change Research

By Gayathri Vaidyanathan and ClimateWire | April 23, 2015

http://www.scientificamerican.com/article/how-to-misinterpret-climate-change-research/
References

 [1] Anthropogenic sulfur dioxide emissions: 1850–2005

http://www.atmos-chem-phys.net/11/1101/2011/acp-11-1101-2011.pdf

[2] The last decade of global anthropogenic sulfur dioxide: 2000–2011 emissions

http://iopscience.iop.org/1748-9326/8/1/014003/article

[3] Trend in Global Black Carbon Emissions from 1960 to 2007

Rong Wang et al

Environ. Sci. Technol., 2014, 48 (12), pp 6780–6787

DOI: 10.1021/es5021422

Publication Date (Web): May 13, 2014

http://pubs.acs.org/doi/abs/10.1021/es5021422

[4] Study estimates global black carbon emissions up 72% from 1960-2007; BC emissions intensity down 52%

Green Car Congress - 31 May 2014

http://www.greencarcongress.com/2014/05/20140531-bc.html

[5] Global tracking of the SO2 clouds from the June, 1991 Mount Pinatubo eruptions

Gregg J. S. Bluth

Article first published online: 7 DEC 2012

DOI: 10.1029/91GL02792

http://onlinelibrary.wiley.com/doi/10.1029/91GL02792/abstract

[6] An overview of geoengineering of climate using stratospheric sulfate aerosols

Philip J Rasch et al

The Royal Society – Philosophical Transactions A

DOI: 10.1098/rsta.2008.0131 Published 13 November 2008

http://rsta.royalsocietypublishing.org/content/366/1882/4007

“For example, the eruption of Mount Pinatubo is believed to have injected approximately 10 Tg S (in the form of SO2) over a few days”

[6a] The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines

USGS - U.S. Geological Survey Fact Sheet 113-97

http://pubs.usgs.gov/fs/1997/fs113-97/

[7] Emissions from volcanoes

Christiane Textor, Hans-F. Graf, Claudia Timmreck, Alan Robock

Emissions of Atmospheric Trace Compounds

Advances in Global Change Research Volume 18, 2004, pp 269-303

http://link.springer.com/chapter/10.1007/978-1-4020-2167-1_7

[8] A Case for Climate Engineering

David Keith (2014)

https://books.google.com/books?id=JXf6AAAAQBAJ&printsec=frontcover&dq=A+Case+for+Climate+Engineering++By+David+Keith&hl=en&sa=X&ei=GmEQVcOpPISWgwTz1IGAAg&ved=0CCcQ6AEwAA#v=onepage&q=A%20Case%20for%20Climate%20Engineering%20%20By%20David%20Keith&f=false

[9] Possible influence of anthropogenic aerosols on cirrus clouds and anthropogenic forcing

J. E. Penner – Feb 3, 2009

Atmos. Chem. Phys., 9, 879-896, 2009

www.atmos-chem-phys.net/9/879/2009/

doi:10.5194/acp-9-879-2009

http://www.atmos-chem-phys.net/9/879/2009/acp-9-879-2009.html

[9a] Thin, Low Arctic Clouds Played an Important Role in Widespread 2012 Greenland Ice Sheet Melt

National Science Foundation - Press Release 13-060 - April 3, 2013

http://www.nsf.gov/news/news_summ.jsp?cntn_id=127438

[10] Does air pollution—specifically particulate matter (aerosols)—affect global warming?

Summary prepared by M. Baker (University of Washington) and reviewed by B. Ekwurzel, N. Cole, P. Frumhoff, and S. Shaw (UCS).

Union of Concerned Scientists 

http://www.ucsusa.org/global_warming/science_and_impacts/science/aerosols-and-global-warming-faq.html#.VPpy5PnF8co 

http://www.bolin.su.se/index.php/past-workshops/274-workshop-high-latitude-volcanic-eruptions-and-climate-filling-the-gaps-5-6-november-2014

[11] Estimates of residence times of sulfate aerosols in ambient air

E.A. Bondietti∗, C. Papastefanou∗∗

Science of The Total Environment

Volume 136, Issues 1–2, 15 August 1993, Pages 25–31

doi:10.1016/0048-9697(93)90294-G

http://www.sciencedirect.com/science/article/pii/004896979390294G

[12] Winter warming from large volcanic eruptions

Alan Robock and Jianping Mao - 7 DEC 2012

DOI: 10.1029/92GL02627

http://onlinelibrary.wiley.com/doi/10.1029/92GL02627/abstract

[13] Workshop “High-latitude volcanic eruptions and climate: filling the gaps”, 5–6 November 2014

Bolin Center for Climate Research

http://www.bolin.su.se/index.php/past-workshops/274-workshop-high-latitude-volcanic-eruptions-and-climate-filling-the-gaps-5-6-november-2014

[14] New study blames 10-year lull in global warming on China coal use, air pollution

By Andrew Freedman – Capital Weather Gang – WP – 07/05/2011

http://www.washingtonpost.com/blogs/capital-weather-gang/post/new-study-blames-10-year-lull-in-global-warming-on-china-coal-use-air-pollution/2011/07/05/gHQAwjV8yH_blog.html

[15] Global is the new local: Pollution changes clouds, climate downstream

By Carol Rasmussen, - NASA's Earth Science News Team - January 26, 2015

http://climate.nasa.gov/news/2218/

[16] Volcanic aerosols, not pollutants, tamped down recent Earth warming, says CU study

March 1, 2013 - Natural Sciences, Environment, Institutes, Cooperative Institute for Research in Environmental Science (CIRES)

http://www.colorado.edu/news/releases/2013/03/01/volcanic-aerosols-not-pollutants-tamped-down-recent-earth-warming-says-cu#sthash.PmHnyQE0.dpuf

[17] Volcanic contribution to decadal changes in tropospheric temperature

Published online 23 February 2014

Benjamin D. Santer et al - Nature Geoscience 7, 185–189 (2014) doi:10.1038/ngeo2098

http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2098.html

[18] Cool Pacific Ocean Slowed Global Warming

By Becky Oskin – Live Science - February 26, 2015

http://www.livescience.com/49967-pacific-ocean-global-warming-pause.html

[19] Cause of global warming hiatus found deep in the Atlantic Ocean 

Phys.Org – Aug 21, 2014

http://phys.org/news/2014-08-global-hiatus-deep-atlantic-ocean.html

[20] Global warming likely to accelerate after “pause”, say scientists

By Sophie Yeo – RTCC - Last updated on 24 February 2015

http://www.rtcc.org/2015/02/24/global-warming-likely-to-accelerate-after-pause-say-scientists/#sthash.YIIK6oGM.dpuf

[21] Sulphur oxides (SOx) – Regulation 14

IMO International Maritime Organization

http://www.imo.org/OurWork/Environment/PollutionPrevention/AirPollution/Pages/Sulphur-oxides-%28SOx%29-%E2%80%93-Regulation-14.aspx

[22] Ocean Acidification

Summary for Policymakers

Third Symposium on the Ocean in a High-CO2 World

The International Geosphere-Biosphere Programme (IGBP)

http://www.igbp.net/download/18.30566fc6142425d6c91140a/1385975160621/OA_spm2-FULL-lorez.pdf

[23] Arctic sea ice winter maximum may be record low

Yereth Rosen - Alaska Dispatch News - March 9, 2015

https://www.adn.com/article/20150309/arctic-sea-ice-winter-maximum-may-be-record-low

[24] U.S. Drought Monitor

http://droughtmonitor.unl.edu/

[25] Little relief in Central America's food crisis

By Claire Luke - 19 February 2015

https://www.devex.com/news/little-relief-in-central-america-s-food-crisis-85387

[26] Taps Start to Run Dry in Brazil’s Largest City

By SIMON ROMEROFEB. 16, 2015

http://www.nytimes.com/2015/02/17/world/americas/drought-pushes-sao-paulo-brazil-toward-water-crisis.html?_r=0

[27] A new Geoengineering Model Intercomparison Project (GeoMIP) experiment designed for climate and chemistry models

S. Tilmes et al.

Geosci. Model Dev., 8, 43–49, 2015

www.geosci-model-dev.net/8/43/2015/

doi:10.5194/gmd-8-43-2015

[28] 4. Post-Implementation Stage - Termination Problem

Ethics of Geoengineering Online Resource Center

University of Montana

http://www.umt.edu/ethics/resourcecenter/why_ethics/post_implementation.php

[29] Geoengineering: issues of path-dependence and socio-technical lock-in

Rose Cairns (SPRU – Science and Technology Policy Research)

October 2013

http://geoengineering-governance-research.org/perch/resources/background-briefing.pdf

Wires Climate Change - Advanced Review

Published Online: Jun 27 2014

DOI: 10.1002/wcc.296

http://wires.wiley.com/WileyCDA/WiresArticle/wisId-WCC296.html

[30] Fossil Fuel Subsidies Are Twelve Times Renewables Support

by Bloomberg News - July 29, 2010

http://www.bloomberg.com/news/articles/2010-07-29/fossil-fuel-subsidies-are-12-times-support-for-renewables-study-shows

[31] Energy subsidies aren’t just for renewables, fossil fuels get the lion’s share

By The BDN Editorial Board,

Posted Feb. 19, 2015

 http://www.worldfinance.com/home/fossil-fuels-arent-going-anywhere

[32] Fossil fuel clampdown could finally be on its way

By Matt TimmsThursday, World Finance - February 26th, 2015

http://www.worldfinance.com/home/fossil-fuels-arent-going-anywhere

[33] Shell oil drilling in Arctic set to get US government permission

By Terry Macalister – The Guardian – March 22, 2015

http://www.theguardian.com/business/2015/mar/22/shell-oil-driling-in-arctic-set-to-get-us-government-permission

[34] The Melting Arctic: A Fragile Frontier of Riches and Risk Opens for Business

By Sabrina Shankman, InsideClimate News - Mar 17, 2015

http://insideclimatenews.org/news/17032015/melting-arctic-fragile-frontier-riches-and-risk-opens-business

[35] China Can Play Key Role in Arctic Shipping

By MarEx 2015-03-21

http://www.maritime-executive.com/features/china-can-play-key-role-in-arctic

[36] Future Arctic: More Mining, More Shipping and More Tourists

By Benjamin Hulac and ClimateWire - March 13, 2015

http://www.scientificamerican.com/article/future-arctic-more-mining-more-shipping-and-more-tourists/

[37] Could the Arctic be the next Crimea?

BY Duncan Depledge - Postdoctoral researcher, Royal Holloway

Quartz – March 23, 2015

http://qz.com/368022/could-the-arctic-be-the-next-crimea/

[38] Russia's Arctic pivot is a massive military undertaking

JEREMY BENDER – Business Insider - MAR. 12, 2015

http://www.businessinsider.com/russias-arctic-pivot-is-a-massive-military-undertaking-2015-3

[39] Moral Hazard: “In economics, moral hazard occurs when one person takes more risks because someone else bears the burden of those risks. A moral hazard may occur where the actions of one party may change to the detriment of another after a financial transaction has taken place.

Moral hazard occurs under a type of information asymmetry where the risk-taking party to a transaction knows more about its intentions than the party paying the consequences of the risk. More broadly, moral hazard occurs when the party with more information about its actions or intentions has a tendency or incentive to behave inappropriately from the perspective of the party with less information.”

Moral Hazard - From Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Moral_hazard


[40] Dimming the Sun:
How Clouds and Air Pollution Affect Global Climate [40]

Beate Liepert
Senior Research Scientist - Climate & Solar Energy
NorthWest Research Associates
Wednesday, March 25, 2015

http://www.bard.edu/news/events/event.php?eid=128998&date=1427324400

[41] IPCC Fourth Assessment Report (AR4)
Climate Change 2007: The Physical Science Basis
Chapter 3 Observations: Surface and Atmospheric Climate Change

http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg1_report_the_physical_science_basis.htm

[42] Optical Depth
From Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Optical_depth

[43] Glory Mission Science
http://glory.giss.nasa.gov/

Other readings

Climate forcing growth rates: doubling down on our Faustian bargain

Environmental Research Letters Volume 8 Number 1

James Hansen et al 2013 Environ. Res. Lett. 8 011006 doi:10.1088/1748-9326/8/1/011006

http://iopscience.iop.org/1748-9326/8/1/011006

Top Lessons to be Learned from Warming ‘Hiatus’

David Appell  —  Yale Climate Connections --- March 5, 2015

http://www.yaleclimateconnections.org/2015/03/top-lessons-to-be-learned-from-warming-hiatus/#comment-1492782

Added March 30th.


 Equilibrium climate sensitivity in light of observations over the warming hiatus
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2573.html 


 Natural variability, radiative forcing and climate response in the recent hiatus reconciled
http://www.nature.com/ngeo/journal/v7/n9/full/ngeo2228.html 


The Persistently Variable “Background” Stratospheric Aerosol Layer and Global Climate Change
http://www.sciencemag.org/content/333/6044/866.short