Reconstruction of solar irradiance since 1610: Implications for climate change

TLDR

The period studied spans the Maunder Minimum (1645–1715) and the rise to the Modern Maximum of solar activity. Annual solar total and UV irradiances from 1610 onward were reconstructed, separating the Schwabe 11‑year cycle from longer‑term variability using modern solar and stellar observations. Reconstructed irradiance correlates strongly (r = 0.86) with Northern Hemisphere temperatures pre‑industrial, indicating a dominant solar role, and the analysis attributes roughly half of the 0.55 °C warming since 1860 and one‑third since 1970 to solar forcing.

Abstract

Solar total and ultraviolet (UV) irradiances are reconstructed annually from 1610 to the present. This epoch includes the Maunder Minimum of anomalously low solar activity (circa 1645–1715) and the subsequent increase to the high levels of the present Modern Maximum. In this reconstruction, the Schwabe (11‐year) irradiance cycle and a longer term variability component are determined separately, based on contemporary solar and stellar monitoring. The correlation of reconstructed solar irradiance and Northern Hemisphere (NH) surface temperature is 0.86 in the pre‐industrial period from 1610 to 1800, implying a predominant solar influence. Extending this correlation to the present suggests that solar forcing may have contributed about half of the observed 0.55°C surface warming since 1860 and one third of the warming since 1970.