University of Oulu

Egorova, T., Schmutz, W., Rozanov, E., Shapiro, A., Usoskin, I., Beer, J., Tagirov, R., Peter, T. (2018) Revised historical solar irradiance forcing. Astronomy and Astrophysics, 615, A85. doi:10.1051/0004-6361/201731199

Revised historical solar irradiance forcing

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Author: Egorova, T.1; Schmutz, W.1; Rozanov, E.1,2;
Organizations: 1Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Davos Dorf, Switzerland
2Institute for Atmospheric and Climate Science, ETH, Zurich, Switzerland
3Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
4Space Climate Research Unit and Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
5EAWAG, Dübendorf, Switzerland
6Imperial College London, Astrophysics Group, Blackett Laboratory, London, UK
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.1 MB)
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Language: English
Published: EDP Sciences, 2018
Publish Date: 2018-08-07


Context: There is no consensus on the amplitude of historical solar forcing. The estimated magnitude of the total solar irradiance (TSI) difference between the Maunder minimum and the present time ranges from 0.1 to 6 W m⁻² making the simulation of the past and future climate uncertain. One reason for this disagreement is the applied evolution of the quiet Sun brightness in solar irradiance reconstruction models. This work addresses the role of the quiet Sun model choice and updated solar magnetic activity proxies on the solar forcing reconstruction.

Aims: We aim to establish a plausible range for the solar irradiance variability on decadal to millennial timescales.

Methods: The spectral solar irradiance (SSI) is calculated as a weighted sum of the contributions from sunspot umbra, sunspot penumbra, faculae, and quiet Sun, which are pre-calculated with the NLTE Spectral SYnthesis code (NESSY). We introduce activity belts of the contributions from sunspots and faculae and a new structure model for the quietest state of the Sun. We assume that the brightness of the quiet Sun varies in time proportionally to the secular (22-yr smoothed) variation of the solar modulation potential.

Results: A new reconstruction of the TSI and SSI covering the period 6000 BCE – 2015 CE is presented. The model simulates solar irradiance variability during the satellite era well. The TSI change between the Maunder and recent minima ranges between 3.7 and 4.5 W m⁻² depending on the applied solar modulation potential. The implementation of a new quietest Sun model reduces, by approximately a factor of two, the relative solar forcing compared to the largest previous estimation, while the application of an updated solar modulation potential increases the forcing difference between the Maunder minimum and the present by 25–40%.

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Series: Astronomy and astrophysics
ISSN: 0004-6361
ISSN-E: 1432-0746
ISSN-L: 0004-6361
Volume: 615
Article number: A85
DOI: 10.1051/0004-6361/201731199
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: The work was performed in the framework of the Swiss National Science Foundation project under grant agreement CRSII2-147659 (FUPSOL II). ER was partly supported by SNSF projects 149182 (SILA) and 163206 (SIMA). AS acknowledges funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 624817 and the European Research Council under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 715947). IU acknowledges ReSoLVE Centre of Excellence of the Academy of Finland (Project 272157). RVT acknowledges funding from SNF grant 200020–153301.
Academy of Finland Grant Number: 272157
Detailed Information: 272157 (Academy of Finland Funding decision)
Copyright information: © ESO 2018. Published in this repository with the kind permission of the publisher.