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| Titel |
An empirical model of global climate – Part 1: A critical evaluation of volcanic cooling |
| VerfasserIn |
T. Canty, N. R. Mascioli, M. D. Smarte, R. J. Salawitch |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 8 ; Nr. 13, no. 8 (2013-04-18), S.3997-4031 |
| Datensatznummer |
250018593
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| Publikation (Nr.) |
 copernicus.org/acp-13-3997-2013.pdf |
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| Zusammenfassung |
| Observed reductions in Earth's surface temperature following explosive
volcanic eruptions have been used as a proxy for geoengineering of climate
by the artificial enhancement of stratospheric sulfate. Earth cools following
major eruptions due to an increase in the reflection of sunlight caused by a
dramatic enhancement of the stratospheric sulfate aerosol burden. Significant
global cooling has been observed following the four major eruptions since
1900: Santa María, Mount Agung, El Chichón and Mt. Pinatubo,
leading IPCC (2007) to state "major volcanic eruptions can, thus, cause a drop
in global mean surface temperature of about half a degree Celsius that can
last for months and even years". We use a multiple linear regression model
applied to the global surface temperature anomaly to suggest that exchange of
heat between the atmosphere and ocean, driven by variations in the strength
of the Atlantic Meridional Overturning Circulation (AMOC), has been a factor
in the decline of global temperature following these eruptions. The veracity
of this suggestion depends on whether sea surface temperature (SST) in the
North Atlantic, sometimes called the Atlantic Multidecadal Oscillation, but
here referred to as Atlantic Multidecadal Variability (AMV), truly represents
a proxy for the strength of the AMOC. Also, precise quantification of global
cooling due to volcanoes depends on how the AMV index is detrended. If the
AMV index is detrended using anthropogenic radiative forcing of climate, we
find that surface cooling attributed to Mt. Pinatubo, using the Hadley
Centre/University of East Anglia surface temperature record, maximises at
0.14 °C globally and 0.32 °C over land. These values are
about a factor of 2 less than found when the AMV index is neglected in the
model and quite a bit lower than the canonical 0.5 °C cooling usually
attributed to Pinatubo. This result is driven by the high amplitude, low
frequency component of the AMV index, demonstrating that reduced impact of
volcanic cooling upon consideration of the AMV index is driven by variations
in North Atlantic SST that occur over time periods much longer than those
commonly associated with major volcanic eruptions. The satellite record of
atmospheric temperature from 1978 to present and other century-long surface
temperature records are also consistent with the suggestion that volcanic
cooling may have been over estimated by about a factor of 2 due to prior
neglect of ocean circulation. Our study suggests a recalibration may be
needed for the proper use of Mt. Pinatubo as a proxy for geoengineering of
climate. Finally, we highlight possible shortcomings in simulations of
volcanic cooling by general circulation models, which are also being used to
assess the impact of geoengineering of climate via stratospheric sulfate
injection. |
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