Abstract
Total Solar Irradiance (TSI) quantifies the solar energy received by the Earth and therefore is of direct relevance for a possible solar influence on climate change on Earth. We analyse the TSI space measurements from 1991 to 2021, and we derive a regression model that reproduces the measured daily TSI variations with a Root Mean Square Error (RMSE) of 0.17 W/m2. The daily TSI regression model uses the MgII core to wing ratio as a facular brightening proxy and the Photometric Sunspot Index (PSI) as a measure of sunspot darkening. We reconstruct the annual mean TSI backwards to 1700 based on the Sunspot Number (SN), calibrated on the space measurements with an RMSE of 0.086 W/m2. The analysis of the 11 year running mean TSI reconstruction confirms the existence of a 105 year Gleissberg cycle. The TSI level of the current grand minimum is only about 0.15 W/m2 higher than the TSI level of the grand minimum in the beginning of the 18th century.
Highlights
The climate on Earth is determined by the balance between the incoming solar radiation—quantified by the Total Solar Irradiance (TSI)—and the outgoing terrestrial radiation
The analysis of the 11 year running mean TSI reconstruction confirms the existence of a 105 year Gleissberg cycle
The annual mean TSI values are more relevant, and those annual mean values will be studied in the current section
Summary
The climate on Earth is determined by the balance between the incoming solar radiation—quantified by the Total Solar Irradiance (TSI)—and the outgoing terrestrial radiation. A change in TSI is a solar force of climate change on Earth; the TSI needs to be monitored as an Essential Climate Variable (ECV) [1]. The first measurement of TSI from space was made in 1969 [2], and continuous monitoring of the TSI with space radiometers started in 1978 [3]. TSI radiometers measure at different absolute levels [4], and are subject to ageing due to solar exposure [5]. There is a short-term TSI decrease—referred to as sunspot darkening—when a sunspot characterised by a strong surface magnetic field occurs. There is a longer-term TSI increase—referred to as facular brightening—caused by the facula, characterised by an intermediate-strength magnetic field, which form when a sunspot decays and which have a significantly longer lifetime than the original sunspot
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
