Volcanic eruptions are an important natural cause of climate change on many timescales. A new capability to predict the climatic response to a large tropical eruption for the succeeding 2 years will prove valuable to society. In addition, to detect and attribute anthropogenic influences on climate, including effects of greenhouse gases, aerosols, and ozone-depleting chemicals, it is crucial to quantify the natural fluctuations so as to separate them from anthropogenic fluctuations in the climate record. Studying the responses of climate to volcanic eruptions also helps us to better understand important radiative and dynamical processes that respond in the climate system to both natural and anthropogenic forcings. Furthermore, modeling the effects of volcanic eruptions helps us to improve climate models that are needed to study anthropogenic effects. Large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with an e-folding residence time of about 1 year. Large ash particles fall out much quicker. The radiative and chemical effects of this aerosol cloud produce responses in the climate system. By scattering some solar radiation back to space, the aerosols cool the surface, but by absorbing both solar and terrestrial radiation, the aerosol layer heats the stratosphere. For a tropical eruption this heating is larger in the tropics than in the high latitudes, producing an enhanced pole-to-equator temperature gradient, especially in winter. In the Northern Hemisphere winter this enhanced gradient produces a stronger polar vortex, and this stronger jet stream produces a characteristic stationary wave pattern of tropospheric circulation, resulting in winter warming of Northern Hemisphere continents. This indirect advective effect on temperature is stronger than the radiative cooling effect that dominates at lower latitudes and in the summer. The volcanic aerosols also serve as surfaces for heterogeneous chemical reactions that destroy stratospheric ozone, which lowers ultraviolet absorption and reduces the radiative heating in the lower stratosphere, but the net effect is still heating. Because this chemical effect depends on the presence of anthropogenic chlorine, it has only become important in recent decades. For a few days after an eruption the amplitude of the diurnal cycle of surface air temperature is reduced under the cloud. On a much longer timescale, volcanic effects played a large role in interdecadal climate change of the Little Ice Age. There is no perfect index of past volcanism, but more ice cores from Greenland and Antarctica will improve the record. There is no evidence that volcanic eruptions produce El Nino events, but the climatic effects of El Nino and volcanic eruptions must be separated to understand the climatic response to each.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1998RG000054

Volcanic eruptions and climate

Adverse health effects of outdoor air pollutants.

[1] The 1783–1784 Laki flood lava eruption in Iceland emitted ∼122 megatons (Mt) SO2 into the atmosphere and maintained a sulfuric aerosol veil that hung over the Northern Hemisphere for >5 months. The eruption columns extended to 9–13 km and released ∼95 Mt SO2 into the upper troposphere/lower stratosphere (i.e., the polar jet stream), enforcing a net eastward dispersion of the plumes which reacted with atmospheric moisture to produce ∼200 Mt of H2SO4 aerosols. Away from source, the Laki aerosols were delivered to the surface by subsiding air masses within anticyclones. We show that ∼175 Mt of H2SO4 aerosols were removed as acid precipitation and caused the extreme volcanic pollution (i.e., dry fog) that effected Europe and other regions in 1783. The remaining ∼25 Mt stayed aloft at tropopause level for >1 year. The summer of 1783 was characterized by extreme and unusual weather, including an unusually hot July in western Europe, most likely caused by perseverance of southerly air currents. The following winter was one of the most severe winters on record in Europe and North America. In these regions, the annual mean surface cooling that followed the Laki eruption was about −1.3°C and lasted for 2–3 years. We propose that the upper troposphere/lower stratosphere aerosols from Laki disrupted the thermal balance of the Arctic regions for two summers and were the main mechanism for the associated climate perturbations. Eruptions of Laki magnitude have occurred in the recent past in Iceland and will occur again. If such an eruption were to occur today, one of the most likely immediate consequences would be disruption to air traffic over large portions of the Northern Hemisphere.

/pdf/atmospheric-and-environmental-effects-of-the-1783-1784-laki-1rqxju967w.pdf

Atmospheric and environmental effects of the 1783-1784 Laki eruption: A review and reassessment

Chapter 1 Marking out the middle classes in a global city Chapter 2 Gentrification: a middle-cass coping strategy? Chapter 3 Spatial and strategic middle-class activity in the City Chapter 4 Mapping the neighbourhoods Chapter 5 A Class in and for itself? Chapter 6 Home and household Chapter 7 Children, schooling and social reproduction Chapter 8 Making sense of 21st century gentrification Chapter 9 Conclusions Bibliography

London Calling: The Middle Classes and the Remaking of Inner London

Halogens in volcanic systems

This paper investigates the impact of the 1783 eruption of the Laki volcanic fissure in Iceland. This was the most violent, extensive and prolonged volcanic episode which has occurred in the northern hemisphere during the modern era. A detailed examination of newspaper accounts and other documentary evidence reveals the dramatic effect of the eruption on the weather over much of Western Europe. It is shown that Icelandic volcanic eruptions can cause serious environmental damage and extreme climatic disturbance in locations far from the source. Moreover, the evidence indicates a variety of human responses to the weather conditions ranging from panic to attempts to find a scientific explanation.

An Amazing and Portentous Summer: Environmental and Social Responses in Britain to the 1783 Eruption of an Iceland Volcano

Waits, musicians, bearwards and players: the inter-urban road travel and performances of itinerant entertainers in sixteenth and seventeenth century England

Royal post-horse routes in England and Wales: the evolution of the network in the later-sixteenth and early-seventeenth century

Cet article etudie l'impact de la pollution aerienne volcanogene sur l'environnement europeen. Durant l'annee 1783, un brouillard toxique compose de gaz et d'aerosols volcaniques a cause en Europe des maladies respiratoires, des dommages aux recoltes, des mouvements de panique et des perturbations climatiques. Des evenements semblables sont intervenus dans le passe et doivent etre pris en compte par les archeologues et les historiens.

Modelling the distal impacts of past volcanic gas emissions : Evidence of Europe-wide environmental impacts from gases emitted during the eruption of Italian and Icelandic volcanoes in 1783

Mark Brayshay

Papers

An Amazing and Portentous Summer: Environmental and Social Responses in Britain to the 1783 Eruption of an Iceland Volcano

Waits, musicians, bearwards and players: the inter-urban road travel and performances of itinerant entertainers in sixteenth and seventeenth century England

Royal post-horse routes in England and Wales: the evolution of the network in the later-sixteenth and early-seventeenth century

Modelling the distal impacts of past volcanic gas emissions : Evidence of Europe-wide environmental impacts from gases emitted during the eruption of Italian and Icelandic volcanoes in 1783

The European City