On Apr 24, 12:12*am, wrote:
On Apr 23, 1:33*am, Alastair wrote:
* * * * How much of a correlation is there between solar activity,
i.e. sunspots and solar flares etc, and solar output. *No-one ever
seems to explain this and I have a suspicion that there is lot more to
it than merely assuming the sun is hotter when it is active, i.e.
spotty, and cooler when quiescent. *The *coincidence of the Maunder
Minimum and a particularly cold period in Europe may be no more than
that, a coincidence. *It was not possible to measure solar output in
the 17th century but are there any modern measurements that show that
the sun could have been cooler? *Should we assume that fewer spots
equals dimmer?
Tudor Hughes, Warlingham, Surrey.
It was thought in the 20th Century that since sunspots are dark then
more of them would mean less radiation and a cooler world. *But that
seems to be the converse of the truth. *The Maunder Minimum, a name
chosen for its alliteration, was given as an example of why less
sunspots means a cooler world.
The idea that the radiation from the sun is a constant (solar
constant) is based on an 18th Century concept that God created the
world and then let it like run a clockwork machine, al la Newton.
Cheers, Alastair.
* * * *That hardly answers my question. * Is there any *independent*
corroboration of a reduced solar output during 1645-1715? * In any
case a climatic deterioration had set in well before the Maunder
Minimum. * As far as I know there is no verification of the sun's
output being reduced during that period and futhermore it seems that
there is very little variation in solar output during a solar cycle or
from one cycle to the next, regardless of its intensity. *It would be
nice if someone could *confirm this, or deny it, come to that. *This
is like trying to get blood out of a stone and there seems to be
widespread ignorance and confusion on the issue.
Tudor Hughes, Warlingham, Surrey.
Tudor,
At the last Wednesday Meeting of the RMetSoc the FRS speakers were
using extracts from Wikipedia in their presentations.
If you look up Maunder Minimum there, you will find this answer to
your question:
Little Ice Age
The Maunder Minimum coincided with the middle — and coldest part — of
the Little Ice Age, during which Europe and North America, and perhaps
much of the rest of the world, were subjected to bitterly cold
winters. Whether there is a causal connection between low sunspot
activity and cold winters is the subject of ongoing debate (e.g., see
Global Warming).
http://en.wikipedia.org/wiki/Maunder_minimum
The relationship between sunspots ant their effect on the Earth is
described in the Solar Cycle article:
Solar irradiance
The total solar irradiance (TSI) is the amount of solar radiative
energy incident on the Earth's upper atmosphere. TSI variations were
undetectable until satellite observations began in late 1978. The
major finding of satellite observations is that TSI varies in phase
with the solar magnetic activity cycle[6] with an amplitude of about
0.1 % and an average value of about 1366 W/m2. Variations about the
average up to - 0.3 % are caused by large sunspot groups and of + 0.05
% by large faculae and bright network on a week to 10 day timescale[7]
(see TSI variation graphics [1].) The sunspot cycle variation of 0.1%
has small but detectable affects on the Earth's climate [8]. TSI
variations over the several decades of continuous satellite
observation show small but detectable trends[9][10] that if sustained
on longer timescales could be a significant forcing for climate
change.
TSI is higher at solar maximum, even though sunspots are darker
(cooler) than the average photosphere. This is caused by magnetized
structures other than sunspots during solar maxima, such as faculae
and active elements of the 'bright' network, that are brighter
(hotter) than the average photosphere. They collectively
overcompensate for the irradiance deficit associated with the cooler
but less numerous sunspots. The primary driver of TSI changes on solar
rotational and sunspot cycle timescales is the varying photospheric
coverage of these radiatively active solar magnetic structures.
http://en.wikipedia.org/wiki/Solar_cycle
Another idea for the cause of the Little Ice Age is that it was due to
the Black Death. See Wikipedia:
Ruddiman has theorized that depopulation of Europe, East Asia, and the
Middle East during the Black Death, with the resulting decrease in
agricultural output and reforestation taking up more carbon from the
atmosphere, may have been a major factor in the slight cooling noted
during the Little Ice Age. Ruddiman further theorizes that massive
depopulation in the Americas after the European contact in the early
1500s had similar effects. A 2008 study of sediment cores and soil
samples further suggests that carbon sequestration via reforestation
in the Americas contributed to the Little Ice Age.
http://en.wikipedia.org/wiki/Little_Ice_Age#Causes
HTH,
Cheers, Alastair.