Observations of a stratospheric aerosol veil from a tropical volcanic eruption in December 1808: is this the "Unknown" ~1809 eruption?

Abstract

Abstract. The "Unknown" eruption of 1808/1809 was the second most explosive SO2-rich volcanic eruption in the last two centuries, only eclipsed by the cataclysmic VEI 7 Tambora eruption in April 1815. However, no eyewitness accounts of the event, and therefore its location, or the atmospheric optical effects associated with its aerosols have been documented from historical records. Here we report on two meteorological observations dating from the end of 1808 that describe phenomena we attribute to volcanic-induced atmospheric effects caused by the Unknown eruption. The observations were made by two highly respected Latin American scientists. The first, Francisco José de Caldas, describes a stratospheric aerosol haze, a "transparent cloud that obstructs the sun's brilliance", that was visible over the city of Bogotá, Colombia, from 11 December 1808 to at least mid-February 1809. The second, made by physician José Hipólito Unanue in Lima, Peru, describes sunset after-glows (akin to well-documented examples known to be caused by stratospheric volcanic aerosols) from mid-December 1808 to February 1809. These two accounts provide direct evidence of a persistent stratospheric aerosol veil that spanned at least 2600 km into both Northern and Southern Hemispheres and establish that the source was a tropical volcano. Moreover, these observations confirm that the Unknown eruption, previously identified and tentatively assigned to February 1809 (±4 months) from analysis of ice core sulphate records, occurred in late November or early December 1808 (4 December 1808 ± 7 days). This date has important implications for the associated hemispheric climate impacts and temporal pattern of aerosol dispersal.

A Reconstruction of Subtropical Western North Pacific SST Variability Back to 1578, Based on a Porites Coral Sr/Ca Record from the Northern Ryukyus, Japan

“…Most simulations aimed at reproducing tree ring and ice core proxy archives find that volcanic forcing is the major driver of short‐lived temperature changes in the Northern Hemisphere for the past ~1,000 years (e.g., Schneider et al, ; Schurer et al, ). Tree ring density temperature reconstructions (Neukom et al, ; Wilson et al, ) show a protracted cooling during the Dalton Minimum (circa 1807–1832) that has been related to three major explosive volcanic eruptions in 1808–1809 (unknown tropical volcano) (Guevara‐Murua et al, ), in 1815 (Tambora) (Raible et al, ), and in 1835 (Cosigüina) (Longpré et al, ). Although the response of summer temperatures to large explosive volcanic eruptions is a coherent cooling over East Asia and the tropical ocean (Man et al, ), the figure obtained in these simulations for South Japan is only −0.5°C, which is within the uncertainties associated with coral‐derived SSTs.…”

Situating 1816, the ‘year without summer’, in the UK

“…, 83), since comparable records began about 1750 (Briffa and Jones ), and perhaps even in the last 500 years (Guevara‐Murua et al . ). Oppenheimer () recognises the summers of 1817 and 1818 as abnormally cold in the northern hemisphere.…”

“… We concentrate on the 10‐year period 1809–18 so as to include possible effects of the ‘unknown’ eruption of 1808/9 (Guevara‐Murua et al . ) and interesting weather events of that year in the UK. …”

The last millennium climate reanalysis project: Framework and first results

“…A fundamental advantage of the PDA approach is to enable dynamically consistent reconstructions of multivariate states from the proxy record. We demonstrate this by examining multivariate fields for a specific historical event: the mystery volcanic eruption of 1808/1809 [ Guevara‐Murua et al , ]. The global 2 m air temperature and 500 hPa geopotential height field are shown in Figure for 1808–1813, with anomalies relative to the 10 year mean preceding 1808.…”