A Discussion of Implausible Total Solar-Irradiance Variations Since 1700

Chatzistergos, Theodosios

doi:10.1007/s11207-024-02262-6

Cited by 3 publications

(1 citation statement)

References 111 publications

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“…Within the telescopic era, we witnessed a grand solar minimum, "the Maunder Minimum" (Eddy 1976;Usoskin et al 2015), that is, an important period for the understanding of solar dynamo, long-term solar activity, and the solar influence on Earth (Charbonneau 2020;Chatzistergos et al 2023;Karak 2023;Usoskin 2023;Chatzistergos 2024). This is the only grand minimum period recorded in the telescopic era (Usoskin 2023).…”

Section: Introductionmentioning

confidence: 99%

Understanding Solar Activity after the Maunder Minimum: Sunspot Records by Rost and Alischer

Carrasco,

Aparicio,

Chatzistergos

et al. 2024

ApJ

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The Maunder Minimum was a period with significantly reduced solar activity between 1645 and 1715, approximately. The transition between the low solar activity in the Maunder Minimum and the subsequent “normal” regime of solar activity was gradual. However, there are discrepancies in the solar activity level from sunspot number indices and solar activity proxies in that period. Among the contemporaneous observers, Johann L. Rost and Sebastian Alischer were two key sunspot observers to understand the solar activity in this transition just after the Maunder Minimum. We have revised all their sunspot records, counting the number of groups and individual sunspots to derive reliable data for the solar activity level for the period 1716–1726. We found significant misinterpretations of the sunspot group counting assigned to these astronomers in the existing group number databases. Our new group sunspot counting significantly reduces the number of groups for Rost and Alischer’s observations compared to entries in existing databases. Furthermore, our sunspot number estimates (obtained from the active day fraction methodology) of the maximum amplitude of Solar Cycles −3 and −4 are significantly lower than the amplitudes according to the official sunspot number, but they are compatible with sunspot number values obtained from solar activity proxies such as radioisotopes. Our result would imply that solar activity after the Maunder Minimum recovered more gradually and with a lower intensity than previously considered.

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Section: Introductionmentioning

confidence: 99%

Understanding Solar Activity after the Maunder Minimum: Sunspot Records by Rost and Alischer

Carrasco,

Aparicio,

Chatzistergos

et al. 2024

ApJ

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Understanding the secular variability of solar irradiance: the potential of Ca II K observations

Chatzistergos,

Krivova,

Ermolli

2024

J. Space Weather Space Clim.

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With the increasing concern about climate change it is important to have accurate information on the individual contributions by the potential driving agents, solar variability being one of them. Long and reliable records of solar irradiance, which describes the solar radiative energy input into the climate system, are essential for assessing the role of the Sun. The short temporal extent (since the 1970s) of direct space-based irradiance measurements leaves reconstructions of the past variability with the help of models as the only avenue. Such models require information on the surface distribution and evolution of solar magnetic regions, dark sunspots and bright faculae and network. However, such data become increasingly scarce and of diminishing quality further back in time. Prior to the period of direct irradiance measurements, reconstructions mainly rely on sunspot observations or other indirect data to describe facular and network regions. The resulting estimates of the long-term change between the Maunder minimum and the present diverge by about an order of magnitude. Having direct information on bright magnetic regions can help resolving these discrepancies. The by far most promising data for this purpose are the full-disc observations of the Sun in the Ca II K line. Despite the wealth of such data all the way back to 1892, their use up to now has been rather limited, owing to a number of intricacies of the data. Here we review the recent efforts to bring Ca II K datasets to their full potential. We briefly discuss the problems plaguing the data and processing methods that have been developed to account for them before switching to a summary of the products derived from them. Focus is given on reconstructions of total and spectral irradiance variations from Ca II K observations. We summarise most available such reconstructions and discuss various aspects requiring further attention in order to allow Ca II K observations to be used to their full potential and thus eventually more accurate irradiance reconstructions back to 1892.

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Converged ensemble simulations of climate: possible trends in total solar irradiance cannot explain global warming alone

Drótos,

Herein,

Haszpra

et al. 2024

Front. Earth Sci.

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We address the hypothetical question of whether an increasing total solar irradiance (TSI) trend, without anthropogenic contributions, could be sufficient to explain the ongoing global warming. To this end, the intermediate-complexity climate model PlaSim is used. To consider the total internal variability, we present a set of ensemble simulations, with different forcing histories in TSI and CO2 concentration, that have converged sufficiently tightly to the relevant probability distributions to provide a satisfactory bound on any spurious trend possibly arising from a sampling bias; similar bounds on any other unforced contributions to ensemble mean trends are also estimated. A key point is the consideration, among the forcing histories, the steepest increasing trend in TSI that is still consistent with observations according to a recent study; thereby, we essentially revisit corresponding TSI reconstructions, more than 20 years after their last modeling-based evaluation, by improving the analysis through taking care of all possible sources of error or uncertainty and incorporating data that have become available since then. Without any change in CO2 concentration, our TSI trend (i.e., and upper bound on actual TSI trends) is found to be insufficient to produce outcomes compatible with the observational record in global mean surface temperature (GMST) with a nonnegligible probability. We formalize our statement for quantifiers of GMST trends through evaluating their distributions over the ensemble, and we speculate that the hypothesis about the exclusive role of an increasing TSI remains implausible even beyond our particular model setup. At the same time, if we consider a constant TSI, and the observational record in CO2 concentration is applied as forcing, the simulation results and the recorded GMST match well. While we currently need to leave the question of a precise attribution open, we conclude by pointing out that an attribution of the ongoing global warming to an increasing TSI alone could be made plausible only if a bias in the set of land-based instrumental temperature measurements were increasing more rapidly than commonly estimated; an assessment of the latter possibility is out of the scope of our study, as well as addressing solar forcing mechanisms beyond the effect of TSI.

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A Discussion of Implausible Total Solar-Irradiance Variations Since 1700

Cited by 3 publications

References 111 publications

Understanding Solar Activity after the Maunder Minimum: Sunspot Records by Rost and Alischer

Understanding Solar Activity after the Maunder Minimum: Sunspot Records by Rost and Alischer

Understanding the secular variability of solar irradiance: the potential of Ca II K observations

Converged ensemble simulations of climate: possible trends in total solar irradiance cannot explain global warming alone

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