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

Location: Arrhenius building, MISU, C609 
5–6 November 2014
Organization: Francesco S.R. Pausata: This email address is being protected from spambots. You need JavaScript enabled to view it.
Eyjafjallajökull eruption May 2010The potential climate effects of large tropical volcanic eruptions have received wide attention in the scientific climate community over the years and the effect of such powerful but short-lived volcanic eruptions on atmospheric circulation are fairly well understood.  On the other hand, the duration and extent of the climate impacts of large high-latitude volcanic eruptions has been less studied and is thus not fully understood.
The aim of this workshop is to bring together both the most recent model developments and the most recent scientific understanding of the effect of large high-latitude volcanic eruption on climate.
The workshop will be divided in a) morning talks from the guests and b) afternoon round-tables where we discuss in more details the topics presented in the morning and try to  develop common strategies to improve our understanding of high-latitude eruptions/climate interactions.  
The very last part of the workshop will be dedicated to geo-engineering impacts on atmospheric dynamics

Program

Wedneday, November 5
9.30
 
Welcoming and introduction to the workshop
9.45
 
High Latitude Volcanic Eruptions and Climate

Alan Robock, Rutgers University, Department of Environmental Sciences, New Brunswick, NJ

Large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with an e-folding residence time of about one year. The radiative and chemical effects of this aerosol cloud produce responses in the climate system. Using examples from major eruptions of the past and results from experiments with numerical models of the climate system, this talk illustrates the major impacts. Volcanic eruptions produce global cooling, and are an important natural cause of inter-decadal and interannual climate change.

One of the most interesting volcanic effects is the “winter warming” of Northern Hemisphere continents following major tropical eruptions. During the winter in the Northern Hemisphere following every large tropical eruption of the past century, surface air temperatures over North America, Europe, and East Asia were warmer than normal, while they were colder over Greenland and the Middle East. This pattern and the coincident atmospheric circulation correspond to the positive phase of the Arctic Oscillation. High latitude eruptions in the Northern Hemisphere, while also producing global cooling, do not have the same impact on atmospheric dynamics. While high-latitude eruption clouds have a shorter atmospheric  residence time than tropical ones, large high latitude eruptions can weaken the Indian and African summer monsoon, and the effects can be seen in past records of flow in the Nile and Niger Rivers. In fact we can use records of the Nile River flow to provide an improved date for the Eldgjá eruption in Iceland, which we now date at 939 A.D. Since the Mt. Pinatubo eruption in the Philippines in 1991, there have been no large eruptions that affected climate, but the cumulative effects of small eruptions over the past decade had a small effect on global temperature trends

 

10.15
 
Effects of Laki on cloud microphysical properites/climate and risks for human health

Anja Schmidt, University of Leeds, Institute for Climate and Atmospheric Science, Leeds

The eruptions of Eyjafjallajökull in 2010 and Grimsvötn in 2011 in Iceland were stark reminders that society is very vulnerable to volcanic hazards. In this talk I will assess the effects of the 1783–1784 AD Laki eruption on cloud condensation nuclei number concentrations and the subsequent aerosol indirect effects on climate using a state-of-the-art global aerosol microphysics model (GLOMAP). I will also assess the potential impacts of a future Icelandic Laki-type eruption on air quality and human health by combining atmospheric modelling, volcanological data sets, and epidemiology. Depending on the duration of such an eruption, I show that air quality could be degraded for weeks or months to a degree that visibility across Europe may be noticeably reduced and public health is at risk. In excess of 100,000 fatalities could occur in Europe due to such an eruption, depending on the length of exposure of individuals to fine particles.

10.45–11.15
 
Coffee break
11.15
 
Climate effects of large volcanic eruptions on high latitudes

Kirstin Krueger, University of Oslo, Department of Geosciences, Oslo

Large tropical volcanic eruptions have a significant influence on the atmospheric large-scale circulation patterns of the Northern (NH) and Southern Hemisphere, through mechanisms related to the radiative effects of volcanic sulfate aerosols resulting from the direct injection of SO2 into the stratosphere. Of particular interest is the response on the polar winter stratosphere, which also impacts surface climate via dynamical feedbacks. In this study, I will highlight changes of the stratospheric polar vortex, the Brewer Dobson Circulation and the Annular Modes based on comprehensive global aerosol climate and Earth system models simulations. Finally, an outlook will be given for climate effects of large NH extratropical eruptions on high latitudes compared with the effect of tropical eruptions.

 

13.00–17.00
 
Open Discussion
    Contact: Francesco S.R. Pausata: This email address is being protected from spambots. You need JavaScript enabled to view it. for further information or to attend the workshop on Wednesday and Thursday afternoon.
Thursday, November 6
9.30
 
Modeling volcanic eruptions from global aerosol models to earth system models

Claudia Timmreck, Max-Planck-Institute for Meteorology, Hamburg

Large volcanic eruptions are an important driving factor of natural climate variability. A sound assessment of the role of volcanoes in the climate system in comparison to other forcing factors is therefore a prerequisite for understanding future and past climate variability.

New advances in understanding volcanic climate effects have been achieved by using on one hand sophisticated global aerosol models and on the other hand comprehensive climate and Earth system models. An important achievement is thereby the improved understanding of the volcanic imprint on decadal to multi-decadal time scales. New insights have also been gained about the relation between the initial climate state at the time of the eruption, the latitude of eruption and the volcanic climatic impact.

In my talk, I will highlight recent developments in the simulation of the climate effect of volcanic  eruptions with different kind of global models and discuss open questions and research needs. Furthermore, I will outline future planned model intercomparison studies and cross validations of model simulations with observations which are essential to better constrain the radiative forcing of large volcanic eruptions and their climate impact.

 

10.00
 
Simulating the climate responses induced by super volcanic eruptions using a global aerosol model

Myriam Khodri, LOCEAN-IPSL, Paris

It is now generally recognised that volcanic eruptions have an important effect on climatevariability from inter-annual to decadal timescales. Several outstanding questions remain and concern the behaviour of huge SO2 cloud injected into the stratosphere after super eruptions such as those that did occur during the last centuries.To contribute to the on-going effort to reduce the large uncertainties regarding the climatic responses to large volcanic eruptions we performed idealized process-oriented sensitivity experiments using the state-of-the-art IPSL global climate model forced with a well-established global aerosol process model containing a fully explicit size-resolving aerosol microphysical module. We developed experiments aiming at exploring the range of climate sensitivity to the magnitude (amount of SO2 and altitude of the volcanic plume), latitude and season of eruptions. The effects of these eruptions factors were systematically evaluated. Climate simulations reveal that there is no canonical linear relationship between the global cooling and the magnitude of the eruptions, due notably to self-limiting microphysical aerosol processes. These processes explain the relatively weak global cooling that never exceeds 2.5°C in our model for the very large eruptions.

10.30–11.00
 
Coffee break
11.00
 
Volcanic eruptions as an analog for stratospheric geoengineering

Alan Robock, Rutgers University, Department of Environmental Sciences, New Brunswick, NJ

In response to the global warming problem, there has been a recent renewed interest in geoengineering “solutions” involving “solar radiation management” by injecting particles into the stratosphere, brightening clouds or the surface, or blocking sunlight with satellites between the Sun and Earth. No systems to conduct geoengineering now exist, but a comparison of different proposed stratospheric injection schemes, using airplanes, balloons, and artillery, shows that using airplanes to put sulfur gases into the stratosphere would not be expensive. Nevertheless, it would be very difficult to create stratospheric sulfate particles with a desirable size distribution. While volcanic eruptions have been suggested as innocuous examples of stratospheric aerosols cooling the planet, the volcano analog also argues against geoengineering because of ozone depletion, regional hydrologic responses, and other negative consequences. Volcanic eruptions are an imperfect analog, since solar radiation management proposals involve the production of a permanent stratospheric aerosol layer, while volcanic layers are episodic. Nonetheless, we can learn much from the volcanic example about the microphysics of stratospheric sulfate aerosol particles; changes in atmospheric circulation, producing regional climate responses, such as changes to the summer monsoon; atmospheric chemistry; changes of the partitioning of direct and diffuse insolation; effects on satellite remote sensing and terrestrial-based astronomy; and impacts on the carbon cycle. There are 26 reasons why geoengineering may be a bad idea, and five reasons why it might be a good idea.

Some of these can be evaluated with climate modeling, and some using the volcanic analog. Observations of the next large volcanic eruption will help to understand the evolution in stratospheric sulfate aerosol size distribution over the first few months after the eruption. Much more research is needed before we can quantify each of these, so that policymakers in the future can make informed decisions about whether to ever implement stratospheric geoengineering. Given what we know today, global efforts to reduce anthropogenic emissions and to adapt to climate change are a much better way to address anthropogenic global warming.

11.30
 
Geoengineering by sulfate aerosols to stabilize climate in the face of increasing CO2: the impact on the Southern Hemisphere atmosphere and ocean circulation and on the ice shelves in western Antarctica

David Battisti, University of Washington, Department of Atmospheric Sciences, Seattle, WA

When sulfate aerosols are used to ameliorate the global average warming due to increasing CO2, the result is a residual warming in the high latitude northern hemisphere and a residual cooling in the tropics. In the high latitudes of the southern hemisphere, geoengineering by sulfate aerosols exacerbates the atmospheric circulation changes associated with increasing CO2, and may increase the probability that grounded ice sheets in Antarctic would be destabilized, leading to rapid changes in global sea level. Each of these residual effects is due to the different spatial and temporal distribution of the forcing associated with increasing sulfate aerosols and increasing CO2.


13.15–17.00
 
Open Discussion
    Contact: Francesco S.R. Pausata: This email address is being protected from spambots. You need JavaScript enabled to view it. for further information or to attend the workshop on Wednesday and Thursday afternoon.
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