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Old February 9th 18, 04:21 PM posted to alt.talk.weather
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Default Fwd: Why the Sun is growing dim


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From: BurfordTJustice
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alt.comp.freeware,alt.politics.scorched-earth,alt.home.repair,uk.legal,uk.politics.misc,al t.politics.uk
Subject: Why the Sun is growing dim
Date: Thu, 8 Feb 2018 15:15:33 -0500
Organization: A noiseless patient Spider
By 2050, our Sun is expected to be unusually cool.

It's what scientists have termed a 'grand minimum' - a particularly low
point in what is otherwise a steady 11-year cycle.
Over this cycle, the Sun's tumultuous heart races and rests.

At its high point, the nuclear fusion at the Sun's core forces more
magnetic loops high into its boiling atmosphere - ejecting more
ultraviolet radiation and generating sunspots and flares.

When it's quiet, the Sun's surface goes calm. It ejects less ultraviolet
radiation.

Now scientists have scoured the skies and history for evidence of an
even greater cycle amid these cycles.

GRAND MINIMUM

One particularly cool period in the 17th century guided their research.

An intense cold snap between 1645 and 1715 has been dubbed the "Maunder
Minimum".

In England, the Thames river froze over. The Baltic Sea was covered in
ice - so much so that the Swedish army was able to march across it to
invade Denmark in 1658.

***But the cooling was not uniform: Distorted weather patterns warmed up
Alaska and Greenland.***

These records were combined with 20 years of data collected by the
International Ultraviolet Explorer satellite mission, as well as
observations of nearby stars similar to the Sun.

Now physicist Dan Lubin at the University of California San Diego has
calculated an estimate of how much dimmer the Sun is likely to be when
the next such grand minimum takes place.

His team's study, "Ultraviolet Flux Decrease Under a Grand Minimum from
IUE Short-wavelength Observation of Solar Analogs," has been published
in the journal Astrophysical Journal Letters.

It finds the Sun is likely to be 7 percent cooler than its usual minimum.

And another grand minimum is likely to be just decades away, based on
the cooling spiral of recent solar cycles.

SOLAR FALLOUT

A quiet Sun has a noticeable effect on its planets.

For Earth, Lubin says it first thins the stratospheric ozone layer.

This impacts the insulating effect of the atmosphere, with flow-on
effects including major changes to wind and weather patterns.

But it won't stop the current trend of planetary warning, Lubin warns.

"The cooling effect of a grand minimum is only a fraction of the warming
effect caused by the increasing concentration of carbon dioxide in the
atmosphere," a statement from the research team reads.

"After hundreds of thousands of years of CO2 levels never exceeding 300
parts per million in air, the concentration of the greenhouse gas is now
over 400 parts per million, continuing a rise that began with the
Industrial Revolution."

One simulation of a grand minimum on the Earth's current climate
anticipates a reduction of solar warming by 0.25 percent over a 50-year
period between 2020 and 2070.

While the global average surface air temperature appears to cool by
"several tenths of a degree Celsius" in the initial years, this
reduction was rapidly overtaken by ever-increasing trends.

"A future grand solar minimum could slow down but not stop global
warming," the study finds.

"Now we have a benchmark from which we can perform better climate model
simulations," Lubin says. "We can therefore have a better idea of how
changes in solar UV radiation affect climate change."



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