Solar total and spectral irradiance reconstruction over the last 9000 years

Abstract

Context. Changes in solar irradiance and in its spectral distribution are among the main natural drivers of the climate on Earth. However, irradiance measurements are only available for less than four decades, while assessment of solar influence on Earth requires much longer records. Aims. The aim of this work is to provide the most up-to-date physics-based reconstruction of the solar total and spectral irradiance (TSI/SSI) over the last nine millennia. Methods. The concentrations of the cosmogenic isotopes 14 C and 10 Be in natural archives have been converted to decadally averaged sunspot numbers through a chain of physics-based models. TSI and SSI are reconstructed with an updated SATIRE model. Reconstructions are carried out for each isotope record separately, as well as for their composite. Results. We present the first ever SSI reconstruction over the last 9000 years from the individual 14 C and 10 Be records as well as from their newest composite. The reconstruction employs physics-based models to describe the involved processes at each step of the procedure.Conclusions. Irradiance reconstructions based on two different cosmogenic isotope records, those of 14 C and 10 Be, agree well with each other in their long-term trends despite their different geochemical paths in the atmosphere of Earth. Over the last 9000 years, the reconstructed secular variability in TSI is of the order of 0.11%, or 1.5 W/m 2 . After the Maunder minimum, the reconstruction from the cosmogenic isotopes is consistent with that from the direct sunspot number observation. Furthermore, over the nineteenth century, the agreement of irradiance reconstructions using isotope records with the reconstruction from the sunspot number by Chatzistergos et al. (2017) is better than that with the reconstruction from the WDC-SILSO series (Clette et al. 2014), with a lower χ 2 -value.

Characteristic Time Scales of Decadal to Centennial Changes in Global Surface Temperatures Over the Past 150 Years

“…It is clear that the period of a multicentennial phenomenon cannot be determined with only 150 years of data. But evidence that the Medieval Climatic Optimum is global and that there were successive occurrences of cooler and warmer intervals on centennial to millennial time scales has been accumulating (e.g., from Dansgaard et al, , to Masson‐Delmotte et al, , Moberg et al, , or Wu et al, ). We have recalled above that the Hale, Gleissberg (and we can add de Vries) multidecadal to multicentennial components are all present in both solar and climate indices.…”

Solar Angular Momentum Loss over the Past Several Millennia

“…Therefore, the concentration of cosmogenic radionuclides can be used as a proxy for solar variability (see review Beer et al 2012). Wu et al (2018b) reconstructed the first solar modulation potential using multiple cosmogenic radionuclide records (e.g., from tree rings for 14 C, and ice cores for 10 Be), from which the solar open magnetic flux was calculated with a physics-based model (Wu et al 2018a).…”

Analysis of full disc Ca II K spectroheliograms

“…To go further back in time, sunspot observations and isotope data are the typically employed proxies of solar magnetic activity (e.g. Lean et al 1995;Solanki & Fligge 1999;Wang et al 2005;Steinhilber et al 2009;Krivova et al 2007Krivova et al , 2010Delaygue & Bard 2011;Shapiro et al 2011;Vieira et al 2011;Dasi-Espuig et al 2014Cristaldi & Ermolli 2017;Wu et al 2018). However, sunspot observations do not carry information on faculae or the network, whereas isotope data trace primarily the open magnetic flux, which is only indirectly related to sunspot and facular fields.…”