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Modeling Quiet Solar Luminosity Variability

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A new paper, Scafetta et al 2019, reviews the controversy regarding how the total solar irradiance (TSI) has evolved since 1978. One group of scientists believes the TSI slightly decreased from 1980 to 2000 while another group believes the TSI increased. A set of seven satellites monitored TSI over various periods from 1978 to date with different precision. Three ACRIM satellites recorded high quality data in the period 1980-2013, but there was a gap between the ACRIM 1 and ACRIM 2 satellite caused by the delay of launching ACRIM 2 due to the Space Shuttle Challenger disaster. The study reviews three recent proxy models of TSI and concludes that the quiet solar luminosity increased from the 1986 to the 1996 TSI minimum by about 0.45 W/m2 and that 2000–2002 was likely a grand solar maximum.



The Next Solar Cycle And Why it Matters for Climate

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The current solar minimum after solar cycle 24 is one of the deepest solar minima ever observed. Solar scientists' estimates of the new solar cycle 25 vary substantially. Dr. David Whitehouse wrote this report to explain why solar cycle 25 matters to climate. The cold climate during the Little Ice Age coincided with low solar activity. Changes in solar activity can affect climate on Earth by several mechanisms, not just its total heat output. Whitehouse says "Changes of up to 10% occur in the amount of ultraviolet light leaving the Sun over a solar cycle." Climate variability can only be explained if the solar influence is 5 times greater than changes in heat output. "The relative weakness of Cycle 24 took some astronomers by surprise." NOAA predicts that cycle 25 will be weak, similar to cycle 24.



FORCE MAJEURE: The Sun’s Role in Climate Change

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This report by Dr. Henrik Svensmark shows that the solar influence on climate is much larger than is recognized in government and IPCC reports. The report reviews three theories of how the sun can influence climate other than just the total heat output of the sun, called total solar irradiance. Dr. Svensmark says that the effect of sun modulating the galactic cosmic rays that effect cloud formation has received substantial empirical support in recent years. Other solar effects includes the solar ultraviolet changes and the atmospheric electric field effect on clouds. The report discusses the strong correlation between solar activity and global temperatures over the last 12,000 years. Experiments in 2006 showed that cosmic ray can create small aerosols (1 – 2 nm diameter) and later experiments show that when air is exposed to ionizing radiation the aerosol clusters grow much more quickly to become cloud condensation nuclei. This increases cloudiness and affects global temperatures.



Is the Sun driving ozone and changing the climate?

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The Sun affects the ozone layer through changes in UV or charged particles. When the Sun is more active there is more ozone above the equator and less over the poles, and vice versa. An increase in ozone warms the stratosphere or mesosphere, which pushes the tropopause lower. There is thus a solar induced see-saw effect on the height of the tropopause, which causes the climate zones to shift towards then away from the equator, moving the jet streams and changing them from “zonal” jet streams to “meridional” ones. When meridional, the jet streams wander in loops further north and south, resulting in longer lines of air mass mixing at climate zone boundaries, which creates more clouds. Clouds reflect sunlight back out to space, determining how much the climate system is heated by the near-constant incoming solar radiation. Thus the Sun’s UV and charged particles modulate the solar heating of the Earth.



Modulation of Ice Ages via Precession and Dust-Albedo Feedbacks

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The slow wobble, or precession, of the axis of the Earth causes the "Great Year" because it gives warm and cool seasons over its approximate 23,000-year cycle. The advancing ice sheets during a "Great Winter" increases the Earth's albedo, reflecting sunlight and resisting the warming effect of the next "Great Summer". As the ice sheets grow and the seas cool, CO2 also reduces as it is absorbed by the oceans. Most plants suffer severe stress at 190 ppm CO2 and die at 150 ppm, because CO2 is a primary plant-food. The concentration finally reaches the critical 190 ppm level where world flora begins to die and the Gobi steppe-lands turn into a true sand desert. The ensuing dust storms dump thousands of tonnes of dust onto the northern ice sheets each year. The interglacial periods occur only every fourth or fifth Great Year. Ice core data shows that every interglacial warming period is preceded by about 10,000 years of intense dust storms. When the next Great Summer comes along, the dusty polar ice sheets can warm and melt and the next interglacial is born. Low concentrations of CO2 near the end of an ice age causes a die-off of plants leading to dust storms, reducing the ice sheet albedo, resulting in warming and the interglacial periods.



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