Long volcanoes are important source of atmospheric gases, aerosols,

Longbefore now, the influencing  factors  of volcanic eruption is known to be capableof causing changes  in weather andclimate. For over  2000 years ago, Plutarch and others ( Forsyth 1988) pointed outthat the eruption of Mount Etna in 44 B.C. dimmed the Sun and suggested thatthe cooling which resulted from the eruption affectedfarm produce and led to hunger in Rome and Egypt.

Thematerials ejected  from eruptions of volcanoes are important source of atmospheric gases, aerosols, and ash (Sparks, Bursik, Gilbert, Glaze, Sigurdsson and Woods, 1997Schmincke, 2004 and Rose and Durant, 2009). “Volcanicgas emissions from the magma  consist primarily of H2O, followed by CO2, SO2, H2S, HCl, HF, and othercompounds” (Symonds, Rose, Bluth, and  Gerlach, 1994).  Volcanicash is formed by fragmentation processes of the magma and the surrounding  rock material within volcanic vents (Sparks, Bursik, Gilbert, Glaze, Sigurdsson andWoods, 1997 and Zimanowsk, Wohletz, Dellino and Buttner, 2003).  According to Ayris, Lee, Wilson, Kueppers, Dingwell and Delmelle, 2013, Hoshyaripour, 2013 and Aiuppa,Franco, von Glasow et al.,2007, Secondaryproducts like volcanic sulphate aerosols result from high- and low-temperaturechemical transformation processes in the conduit, the volcanic plume, and cloud.  Globalcooling as a result of volcanic eruption is explained as follows by (Robock,2000). According to him, sulphate aerosol particles which are emitted fromvolcanoe scatter solar radiation as they have a radius of around 0.5?m which isapproximately the same size as the wavelength of visible light.

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Some of thelight is backscattered, reflecting sunlight back to space and increasing thenet planetary albedo. Much of the solar radiation is also forward scatteredincreasing downward diffuse radiation partly offsetting the large reduction inthe direct solar beam. The forward scattering effect can be seen by the nakedeye making the normally blue sky a milky white colour. The reflection of thesetting sun from the bottom of the dust veil produces the typical volcanicsunset. “The variations in atmospheric warming and cooling results in changesin tropospheric and stratospheric circulation (Robock, 2000). At the top of the aerosol cloud theatmosphere is heated by absorption of near infra-red solar radiation. In thelower stratosphere the atmosphere is heated by absorption of upward long waveradiation from the troposphere and the surface.

There is also increased InfraRed (IR) cooling due to enhanced emissivity caused by the presence of theaerosols ( Robock 2000). Fig 1. An AerosolcloudSource:Google images.

  Themagnitude of volcanic eruption determine its influence on  the temperature in winter and in summer asseen in the following  scenarios.  Accordingto (Fischer, Luterbacher , Zorita ,  Tett, Casty,  and Wanner, 2007),” there exist a study whichelucidated the climatic response in Europe following15 major tropical eruptions over the last half millennium  from the eruptions  and confirmed the clearpattern of summer temperature cooling during the first and second post-eruptionyears”.  Of these, the strongestsignal of cooling is found during the year after the eruption (Bradley 1988;Robock 2000).  One country known to have experienced summertemperature cooling following the eruptions is Finland. Furthermore,(Helama, Lindholm, Merila¨inen , Timonen and Eronen , 2005; Salzer and  Hughes2007;Helama, La¨a¨nelaid, Ti eta¨va¨inen , Macias Fauria, Kukkonen , Holopainen, Nielsen and  Valovirta I.

2010) opinedthat the distant effects of explosive erruptions hasbeen may have caused the tree rings and their summer temperature reconstructions to exhibited volcanicsignature eruptions in the same area.Moreso, identical eveidences have been observed in regionsbeside Northern  Europe (Gervaisand  MacDonald 2001).Amid- and late-Holocene chronology of climatic downturns. (a) Tree-ringsensitivity (i.e.

, sudden change in growth conditions). Please note that onlynegative departures are given, the values therefore indicating growthreductions. (b) Reconstructed summer (July) temperature variability (blackline) with the green and blue areas indicating the 95% and 99% confidenceintervals of the reconstruction. The study period was 5500 B.C. through 2005A.D.

The years discussed in the text are shown as tree-ring dated calendaryears B.C. and A.D.

     Source:(Helama, Holopainen, Macias-Fauria,  Timonen and  Mielikäinen 2013). “A look at the plot of thetree-ring variability reveals a characteristic paucity of anomalously poorgrowth in terms of dendrochronological sensitivity (Fig.1a).The most negative years of growth are not clustered within a limited period butare spread over several millennia.

Considering the late-Holocene (here, 1–2005A.D.), the tree-ring record shows extreme drops in growth as having occurred in1601 A.D.

and 536 A.D. These years were reconstructed as having been exceptionallycool (Fig.1b).

For both of these years, the summer temperatures were reconstructed to havebeen cooler than 10°C on average, which is more than three standard deviationsfrom the reconstructed mean of 13°C. The year 536 A.D. was followed by anotheryear of reduced growth, in 542 A.D.

, during which the temperatures arereconstructed to have been nearly as cool as six years before” ( Helama,  Holopainen,Macias-Fauria, Timonen and Mielikäinen 2013).     Historically, there hasbeen  significant effects of volcaniceruption in winter, although this modest on scale. Examples are as follows; The1991 explosion of Mount Pinatubo, a stratovolcano in the Philippines, cooledglobal temperatures for about 2–3 years” (Brohan ,  Kennedy, Haris, Tett, and  Jones, 2006). ” In 1883, the explosion ofKrakatoa (Krakatau) created volcanic winter-like conditions The four yearsfollowing the explosion were unusually cold, and the winter of 1887-1888included powerful blizzards” (Hansen, 1997). “Record snowfalls were recordedworldwide”.

  Source:(Google image)  The 1815 eruption of Mount Tambora, astratovolcano in Indonesia, occasioned mid-summer frosts in New York State andJune snowfalls in New England and Newfoundland and Labrador in what came to beknown as the “Year Without a Summer” of 1816. A paper written byBenjamin Franklin in 1783 ( Funkhouser, 2016), blamed the unusually cool summerof 1783 on volcanic dust coming from Iceland, where the eruption of  Laki volcano had released enormous amounts ofsulfur dioxide, resulting in the death of much of the island’s livestock and acatastrophic famine which killed a quarter of the Icelandic population.Northern hemisphere temperatures dropped by about 1 °C in the year followingthe Laki eruption. However Franklin’s proposal has been questioned” (Davis,2008).

In 1600, the Huaynaputina in Peru erupted. Tree ring studies show that1601 was cold. The supervolcano Caldera Lake Toba famine in 1601-1603. From1600 to 1602, Switzerland, Latvia and Estonia had exceptionally cold winters.The wine harvest was late in 1601 in France, and in Peru and Germany, wineproduction collapsed. Peach trees bloomed late in China, and Lake Suwa in Japanfroze early.  (Cantor and  Norman.

L, 2001 ). In 1452 or 1453, acataclysmic eruption of the submarine volcano Kuwae caused worldwidedisruptions. The Great Famine of 1315–1317 in Europe may have been precipitatedby a volcanic event,( Nairn, Shane, Cole, Leonard, Self  and Pearson, 2004  ) perhaps that of Mount Tarawera, NewZealand, lasting about five years(Hodgson and Nairn, 2005).   Question2a.2  answer Thesustenance or diminishing effects of volcanic eruption on global cooling isdetermined by the frequency and magnitude of eruptions.”Volcanic eruptions are a major driver ofclimate variability on a variety of timescales. Large tropical eruptions are capable of injecting sulphur dioxide into the stratospherewhere it forms sulphate aerosol that may persist with an e-folding time ofaround 1 year, spreading globally with a resultant negative radiative forcing(Rampino and Self 1982; Robock 2000).

After the eruption of Mount Pinatuboin 1991, an estimated 20 Mt of SO2  was introduced into the stratosphere (Robock 2000) leading to a global cooling of around0.3 °C (Lehner et al. 2016) and a reduction in globalprecipitation (Trenberth and Dai 2007). Repeated eruptions have shapedclimate evolution, likely causing periods of cooling, such as during the15–19th Centuries (Briffa et al. 1998; Schurer et al.

2014; Miller et al. 2012; Stoffelet al. 2015).

More recently, a series of smallereruptions may have offset a small portion of anthropogenic warming (Solomonet al. 2011; Vernier et al. 2011; Santer et al. 2014). Understanding the influence ofvolcanic eruptions therefore contributes to understanding climate variability(Timmreck 2012; Zanchettin 2017).

The climatic response to volcanicaerosols is complex. The negative radiative forcinginduces several responses in the Earth system (Timmreck 2012; Zanchettin 2017), including expansion of sea-ice(Miller et al. 2012), changes in atmospheric (Robock and Mao, 1992) and ocean circulation (Dinget al. 2014), and perturbations to modes ofvariability (Lehner et al. 2016; Maher et al.

2015). These responses are partly dependenton the climate state prior to an eruption, as well as the location of thevolcano and the season of eruption (Stevenson et al. 2017).

While much attention has focused onshort-term variability, less is known about the influence of longer-termchanges in the background climate (Zanchettin et al. 2013). The future response to an eruptionmay be different because of changes in the climate system caused byanthropogenic warming. Aubry et al. (2016) have recently shown thatwarming-induced changes in the vertical structure of atmosphere (particularlychanges in the tropopause height) would impact on the rise of volcanic plumes, but the impact of future changes on theradiative forcing and response to a volcanic eruption has not been quantified.Here we analyse an ensemble ofcomprehensive Earth System model simulations of a large volcanic eruption toevaluate the climate system response to a largevolcanic eruption in a future climate state. We performed an ensemble ofsimulations with the HadGEM2-ES Earth System model (HadGEM2 Development Team 2011; Collins et al.

2011) of a Tambora 1815 -like eruption inpre-industrial (Kandlbauer et al. 2013) and Representative ConcentrationPathway 6.0 (RCP 6.0) conditions for the years AD1860 and AD2045, respectively.Tambora was chosen because it provides a very strong forcingwhich can be more easily separated from simulated internal variability.ss