Reconstructed and measured total solar irradiance: Is there a secular trend between 1978 and 2003?

TL;DR

This study compares reconstructed total solar irradiance based on magnetic field data with various measurement composites from 1978 to 2003, finding no evidence of a secular trend in the irradiance over this period.

Contribution

It demonstrates that the reconstructed irradiance aligns well with the PMOD/WRC composite and challenges the existence of a secular trend suggested by other measurement composites.

Findings

Good match with PMOD/WRC composite

No secular increase in irradiance in reconstructions

Discrepancies with ACRIM and IRMB composites

Abstract

Total solar irradiance reconstructed between 1978 and 2003 using solar surface magnetic field distributions is compared with three composites of total solar irradiance measurements. A good correspondence is found with the total solar irradiance composite from PMOD/WRC, with no bias between the three cycles. The agreement with the other composites (the ACRIM composite, mainly based on the Active Cavity Radiometer Irradiance Monitors I, II & III, and the IRMB composite from the Institut Royal Meteorologique Belgique) is significantly poorer. In particular, a secular increase in the irradiance exhibited by these composites is not present in the reconstructions. Hence any secular trend in total solar irradiance between 1978 and 2003 is not due to magnetic fields at the solar surface.