The dimmest state of the Sun: TSI and Global warming

This new paper raises some questions about the role of total solar irradiance (TSI) and global warming. OTOH hand its all computer modeling, so take it with a grain of salt. h/t to Dr. Leif Svalgaard.

  • The role of solar forcing in global warning is unclear due to the uncertainty in the change in TSI since the Maunder minimum.
  • The TSI level of the Sun when it is in its least active state is established from an advanced model of TSI variability.
  • This lower limit on grand minima TSI truncates the current range of the possible change in TSI since the Maunder minimum by more than half.

Abstract
How the solar electromagnetic energy entering the Earth’s atmosphere varied since pre industrial times is an important consideration in the climate change debate. Detrimental to this debate, estimates of the change in total solar irradiance (TSI) since the Maunder minimum, an extended period of weak solar activity preceding the industrial revolution, differ markedly, ranging from a drop of 0.75 W m−2
to a rise of 6.3 W m−2.

Consequently, the exact contribution by solar forcing to the rise in global temperatures over the past centuries remains inconclusive. Adopting a novel approach based on state-of23 the-art solar imagery and numerical simulations, we establish the TSI level of the Sun when it is in its least active state to be 2.0±0.7 W m−2 below the 2019 level. This means TSI could not have risen since the Maunder minimum by more than this amount, thus restricting the possible role of solar forcing in global warming.

Plain Language Summary
How the amount of energy the Earth receives from the Sun varied since pre-industrial times is an important consideration in the climate change debate. Detrimental to this debate, it is not known whether the Sun grew brighter or dimmer since the 16th century, and by how much. As a consequence, the exact contribution by fluctuations in the brightness of the Sun to the rise in global temperatures over the past centuries remains controversial. It is established that the Sun was particularly inactive over much of the 16th century. Adopting a novel approach based on state-of-the-art solar imagery and computer models, we determined the brightness of the Sun when it is in its least active state possible. This places a strict limit on how much the Sun could have grown brighter since the lull in solar activity over the 16th century, restricting the possible role the Sun could have played in global warming.

The paper:

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October 6, 2020 at 04:40PM

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