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| Titel |
Impact of solar versus volcanic activity variations on tropospheric temperatures and precipitation during the Dalton Minimum |
| VerfasserIn |
J. G. Anet, S. Muthers, E. V. Rozanov, C. C. Raible, A. Stenke, A. I. Shapiro, S. Brönnimann, F. Arfeuille, Y. Brugnara, J. Beer, F. Steinhilber, W. Schmutz, T. Peter |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 3 ; Nr. 10, no. 3 (2014-05-09), S.921-938 |
| Datensatznummer |
250116970
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| Publikation (Nr.) |
 copernicus.org/cp-10-921-2014.pdf |
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| Zusammenfassung |
| The aim of this work is to elucidate the impact of changes in solar irradiance and energetic particles
versus volcanic eruptions on tropospheric global climate during the Dalton
Minimum (DM, AD 1780–1840). Separate variations in the (i) solar irradiance in
the UV-C with wavelengths λ < 250 nm, (ii) irradiance at
wavelengths λ > 250 nm, (iii) in energetic particle spectrum,
and (iv) volcanic aerosol forcing were analyzed separately, and (v) in
combination, by means of small ensemble calculations using a coupled
atmosphere–ocean chemistry–climate model. Global and hemispheric mean
surface temperatures show a significant dependence on solar irradiance at
λ > 250 nm. Also, powerful volcanic eruptions in 1809, 1815,
1831 and 1835 significantly decreased global mean temperature by up to 0.5 K
for 2–3 years after the eruption. However, while the volcanic effect is
clearly discernible in the Southern Hemispheric mean temperature, it is less
significant in the Northern Hemisphere, partly because the two largest
volcanic eruptions occurred in the SH tropics and during seasons when the
aerosols were mainly transported southward, partly because of the higher
northern internal variability. In the simulation including all forcings,
temperatures are in reasonable agreement with the tree ring-based temperature
anomalies of the Northern Hemisphere. Interestingly, the model suggests that
solar irradiance changes at λ < 250 nm and in energetic particle
spectra have only an insignificant impact on the climate during the Dalton
Minimum. This downscales the importance of top–down processes (stemming from
changes at λ < 250 nm) relative to bottom–up processes (from
λ > 250 nm). Reduction of irradiance at λ > 250 nm
leads to a significant (up to 2%) decrease in the ocean heat content (OHC)
between 0 and 300 m in depth, whereas the changes in irradiance at
λ < 250 nm or in energetic particles have virtually no effect.
Also, volcanic aerosol yields a very strong response, reducing the OHC of the
upper ocean by up to 1.5%. In the simulation with all forcings, the OHC of
the uppermost levels recovers after 8–15 years after volcanic eruption,
while the solar signal and the different volcanic eruptions dominate the OHC
changes in the deeper ocean and prevent its recovery during the DM. Finally,
the simulations suggest that the volcanic eruptions during the DM had a
significant impact on the precipitation patterns caused by a widening of the
Hadley cell and a shift in the intertropical convergence zone. |
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