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The change in total solar irradiance totals hundreds of years – Rising with that?


Open access article published in Atmospheric Remote Sensing

HT / Leif Svalgaard

abstract

Total Solar Irradiation (TSI) quantifies the solar energy received by the Earth and is therefore directly related to the sun’s influence on climate change on Earth. We analyze TSI spatial measurements from 1991 to 2021 and we obtain a regression model that reproduces daily TSI variations measured with a Root Mean Squared Error (RMSE) of 0.17 W /m2. The daily TSI regression model uses the ratio of MgII cores to the wing as a surface brightening quantity and the photometric Sunspot Index (PSI) as a measure of sunspot darkness. We reconstruct the average annual TSI back to 1700 based on Sunspot Number (SN), corrected for spatial measurements with an RMSE of 0.086 W/m2. Analysis of 11 years of active mean TSI reconstruction confirms the existence of a 105 year Gleissberg cycle. The TSI level of the current large minimum is only about 0.15 W/m2 higher than the TSI of the great minimum in the early 18th century.

1. Introduction

Climate on Earth is determined by the balance between incoming solar radiation — quantified by Total Solar Irradiance (TSI) — and radiation coming from the ground. A change in TSI is a solar force of climate change on Earth; therefore, TSI should be tracked as an Essential Climate Variant (ECV). [1].

The first TSI measurement from space was made in 1969 [2]and continuous monitoring of TSI by space irradiometer beginning in 1978 [3]. In general, TSI radiometers measure at different absolute levels [4]and can age due to exposure to solar energy [5]. Some authors have proposed so-called TSI composite time series that quantify long-term TSI changes as measured by space instruments. [5,6,7,8,9].

From the available TSI composites, it is now well established that TSI is phase-varying with an 11-year sunspot cycle. [10]. In particular, there is a short-lived drop in TSI – known as a dark spot – when a sunspot characterized by a strong surface magnetic field appears. There is also an increase in TSI over a longer period – known as a flare – caused by the magnetic field, characterized by a medium intensity magnetic field, which forms as the sunspot decays and ages. Lasts significantly longer than the original black spot.

On top of the 11-year solar cycle TSI variation, there exists a longer term variation of the ‘quiet sun’ [11]. The observed TSI levels over the 11-year minimum period have long been a matter of speculation. Next [12]It is believed that the sun evolved from the so-called ‘Maunder Minimum’ from about 1645 until 1715 when the 11-year cycle amplitude was minimal, to what is known as the ‘Modern Maximum’. [13], where the 11-year cycle amplitude is assumed to be the maximum. Regenerate a hundred-year TSI, such as one of the [14]used to characterize solar climates by the Intergovernmental Panel on Climate Change (IPCC), including a slow rise in the ‘calm sun’ TSI from the Maunder Minimum to the modern max 1.25 W/m2 over a period of about 300 years. Table 1 provides an overview of the increase in TSI since the Maunder minimum found by various studies.

Table 1. The list of studies varies on an increase in TSI since the Maunder Minimum.

Recently, the Sunspot Index and Long-Term Sunspot Number (SILSO) (SN) have been revised. [20,21]. According to the latest details, the Grand Modern Maximum does not exist and therefore the 300-year increase in TSI from Maunder Minimum to Grand Modern Maximum should also be reconsidered. Independent of the SN revision, from an extended 2008–2009 solar minimum analysis, ref. [18] came to the conclusion that the increase in TSI from the Maunder Minimum to date should be revised. In addition, a careful comparison of all space irradiometer TSI time series is available in [9] shows no change in the quiescent sun TSI level over a 32-year period from 1984 to 2016 with a 95% uncertainty of ±0.17 W/m2.

The objective of this paper is to reconstruct the TSI variation hundreds of years back to 1700 based on available TSI spatial measurements and modified SN, consistent with detailed information from [18]. This new centennial TSI reinvention is a paradigm shift [22] versus the long-held belief based on [12] that there has been a significant increase in TSI, and therefore, forced solar climate change, from the Maunder Minimum to the present. In Part 2, we review available TSI spatial measurements and TSI regression models that reproduce sunspots and sunspots from observations of the solar surface magnetic field. In Part 3we rebuilt the TSI variant back to 1700 based on the modified SN.

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4. Discussion

Are from [12]climate research – solar has been dominated by the idea that during the Maunder Minimum, the TSI was significantly lower than present conditions, characterized by the Modern Maximum [13] of solar activity and this lower TSI may at least be responsible for the lower temperatures during the period known as the Little Ice Age (LIA). [48] between the 15th and 19th centuries, the temperature in the Northern Hemisphere decreased by about 0.6°C. For example, in [15]it is estimated that the TSI in the Maunder Minimum could be 3.3 W/m2 lower than its mean between 1980 and 1986. The Modern Maximum Theory had to be abandoned after modifying the sunspot number [20] and after the arrival of the 24 solar low cycle that occurred between 2008 and 2019 — see Figure 3. Therefore, the long-term reconstruction of TSI needs to be revised.

Reconstruction of past TSI variants should be based on analysis of existing TSI spatial measurements. We have demonstrated in Part 2 that the daily composite TSI from 1991 to 2021 can be reproduced with RMSE as low as 0.17 W/m2 and correlation coefficients as high as 0.94 from a regression model based solely on surface lightening proxies and sunspot darkness estimates. There is no evidence that physical effects other than outer surface lightening and sunspot darkening, both related to magnetic fields on the solar surface, are required to explain TSI variations. observable.

We can then try to extrapolate the TSI variants before making a reliable measurement of them from space. On average annual intervals, sunspot luminosity and sunspot darkness are strongly correlated because the surface is the result of sunspot decay over time periods shorter than 1 year. , so a single proxy can be used for both. In Part 3we used two surface lightening proxies — the core-to-wing ratio of MgII and radio flux F10.7 — and a sunspot estimator — SN — to reconstruct the TSI change annual average measured from 1992 to 2020, with an RMSE of 0.071 W/m20.081 W/m2 and 0.086 W/m2, corresponding. Prior to the TSI spatial observations used, the annual TSI extrapolations using any of these proxies agreed well in their overlapping time horizons, giving confidence in the plausibility. of extrapolation. From comparing the sunspot-based TSI model with other TSI estimates over their overlapping time periods, the stability of the annual mean sunspot-based TSI reconstruction is estimated to be ±0.25 W/m2. A TSI reconstruction similar to ours was used in [49] to fully reproduce the global temperature change from 1850 to 2019, increasing confidence in the validity of our TSI reconstruction.

The appearance of the solar system’s minimum and maximum [50,51] can be studied from 11 years of activity mean TSI reconstruction is shown in Figure 5. RMSD analysis as a function of time shift confirms the existence of a 105-year Gleissberg cycle, similar to that found in [45,46]. TSI levels during the preceding minima in the early 18th and 19th centuries were comparable, around 1363.05 W/m2while TSI levels during later minima, early 20th and 21st centuries are also comparable, around 1363.2 W/m2only 0.15 W/m2 higher than the previous minimum. Obviously, this small change in TSI level cannot explain the occurrence of LIA.

The main contribution of our study is that, in contrast to previous studies based on [12]we do not find a significant increase in TSI and hence the effect of solar energy on climate change between Maunder Minimum and present.

5. Conclusion

We obtained a new reconstruction of TSI from 1700 to 2020. It is based on careful comparison and analysis between TSI spatial measurements from 1991 to 2021 and extrapolation back to 1700. on the latest version of the annual average SN. Daily mean TSI spatial measurements can be reproduced with an RMSE of 0.71 W/m2 and the correlation coefficient is 0.94 using a regression model using MgII’s core-wing ratio surface brightness proxy and PSI sunspot darkness estimate. The annual mean TSI model agrees with TSI spatial measurements with an RMSE of 0.086 W/m2 and has an estimated stability of ±0.25 W/m2. Analysis of the 11-year mean TSI reconstruction confirms the existence of a 105-year Gleissberg cycle with a great minima occurring at the beginning of each century. The TSI of the latest major minimum is only 0.15 W/m2 higher than the TSI of the earliest maximum minimum.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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