I would like to draw attention to the following article:
FORCE MAJEURE
The Sun’s Role in Climate Change
by Henrik Svensmark
The Global Warming Policy Foundation
GWPF Report 33
ISBN 978-0-9931190-9-5
© Copyright 2019 The Global Warming Policy Foundation
https://www.thegwpf.org/content/uploads/2019/03/SvensmarkSolar2019.pdf
Executive summary
"Over the last twenty years there has been good progress in understanding the solar influence on climate. In particular, many scientific studies have shown that changes in solar activity have impacted climate over the whole Holocene period (approximately the last 10,000 years). A well-known example is the existence of high solar activity during the Medieval Warm Period, around the year 1000 AD, and the subsequent low levels of solar activity during the cold period, now called The Little Ice Age (1300–1850 AD). An important scientific task has been to quantify the solar impact on climate, and it has been found that over the elevenyear solar cycle the energy that enters the Earth’s system is of the order of 1.0–1.5 W/m2. This is nearly an order of magnitude larger than what would be expected from solar irradiance alone, and suggests that solar activity is getting amplified by some atmospheric process.
Three main theories have been put forward to explain the solar–climate link, which are:
• solar ultraviolet changes
• the atmospheric-electric-field effect on cloud cover
• cloud changes produced by solar-modulated galactic cosmic rays (energetic particles originating from inter stellar space and ending in our atmosphere).
Significant efforts has gone into understanding possible mechanisms, and at the moment cosmic ray modulation of Earth’s cloud cover seems rather promising in explaining the size of solar impact. This theory suggests that solar activity has had a significant impact on climate during the Holocene period. This understanding is in contrast to the official consensus from the Intergovernmental Panel on Climate Change, where it is estimated that the change in solar radiative forcing between 1750 and 2011 was around 0.05 W/m2, a value which is entirely negligible relative to the effect of greenhouse gases, estimated at around 2.3 W/m2. However, the existence of an atmospheric solar-amplification mechanism would have implications for the estimated climate sensitivity to carbon dioxide, suggesting that it is much lower than currently thought.
In summary, the impact of solar activity on climate is much larger than the official consensus suggests. This is therefore an important scientific question that needs to be addressed by the scientific community."