CR 43:263-273 (2010)  -  DOI: https://doi.org/10.3354/cr00938

ABSTRACT: The last 300 yr of the Little Ice Age are characterized by 3 minima in solar activity, known as the Maunder Minimum (~1645–1710), the Dalton Minimum (~1795–1823) and a minimum between ~1880 and 1930. In particular, during the Maunder and Dalton minima, surface temperature reconstructions present anomalies larger than –0.7°C. Experiments using an energy balance model, known as the thermodynamic climate model (TCM), show that the changes in CO₂ and solar irradiance, relative to the period 1961–1990, produced a temperature decrease of approximately –0.27°C during the Maunder Minimum in the Northern Hemisphere. The incorporation of changes in low cloud cover, which we assumed as induced by the galactic cosmic rays, caused an even larger decrease in the surface temperature, which reached approximately –0.46°C in the Maunder Minimum. The results of the model are compared with reconstructions of surface temperature anomalies developed by several authors, showing good agreement. We conclude that including an empirical relationship between low cloud cover and cosmic rays in the TCM produces a noticeable cooling in model results.

KEY WORDS: Maunder and Dalton minima · Atmospheric CO₂ · Solar irradiance · Galactic cosmic rays · Low clouds