Sunspot cycle and solar constant

Does anyone know if the solar constant varies with the sunspot cycle? If
so, by what percentage? I believe the accepted value is 1370 W/sq.meter.

On Thu, 08 Mar 2007 18:10:41 GMT, "TMA-TriMethylAluminum"
wrote:

Does anyone know if the solar constant varies with the sunspot cycle? If
so, by what percentage? I believe the accepted value is 1370 W/sq.meter.

Yes, based on recent satellite measurements (at least for the last few
cycles). The variation is about 0.1%, which is too small to measure from
Earth's surface (the solar constant is increased by about 1 W/m^2 during
solar max).

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

"Chris L Peterson" wrote in message
...
On Thu, 08 Mar 2007 18:10:41 GMT, "TMA-TriMethylAluminum"
wrote:

Does anyone know if the solar constant varies with the sunspot cycle? If
so, by what percentage? I believe the accepted value is 1370 W/sq.meter.

Yes, based on recent satellite measurements (at least for the last few
cycles). The variation is about 0.1%, which is too small to measure from
Earth's surface (the solar constant is increased by about 1 W/m^2 during
solar max).


Has a small variation such as that been proven to affect global climate as
in the Little Ice Age when
sunspots were non-existent?

"Chris L Peterson" wrote in message
...
On Thu, 08 Mar 2007 18:10:41 GMT, "TMA-TriMethylAluminum"
wrote:

Does anyone know if the solar constant varies with the sunspot cycle? If
so, by what percentage? I believe the accepted value is 1370 W/sq.meter.

Yes, based on recent satellite measurements (at least for the last few
cycles). The variation is about 0.1%, which is too small to measure from
Earth's surface (the solar constant is increased by about 1 W/m^2 during
solar max).


Has a small variation such as that been proven to affect global climate as
in the Little Ice Age when
sunspots were non-existent?

On Thu, 08 Mar 2007 23:04:37 GMT, "TriMethylAluminum"
wrote:

Has a small variation such as that been proven to affect global climate as
in the Little Ice Age when sunspots were non-existent?

No. The 11-year solar cycle is now included in most climate models, and
doesn't seem to have much if any impact. Similarly, some proxies for
past solar activity (such as carbon-14 in deep ice) don't show much
correlation between short term sunspot activity and climate. In any
case, the 11-year cycle is probably just too short to influence climate.
But there are a number of longer activity cycles, hundreds or even
thousands of years long. Also, the solar constant changes because our
distance from the Sun changes. Basically, you convolve all these cycles-
either intrinsic to the Sun or geometrical, and you get enough variation
in the solar constant to affect climate. This effect is significant in
long term climate models. The solar constant is probably about 0.3%
higher now than it was at the end of the Little Ice Age, 200-300 years
ago. That period may well have correlated with lower solar activity
(although there is nothing that could be called "proof" of that).

The thing that makes all of these models so tricky is that our climate
is metastable. A seemingly small change in something like green house
gas concentration or solar insolation affects other mechanisms,
resulting in relatively short term positive feedback. The end result is
an ice age or a significant rise in temperature, far out of proportion
with the precipitating cause. That could explain why something like the
Maunder minimum, with a solar constant drop of a couple of tenths of a
percent at most could produce such a profound effect, requiring a long
time to recover from. Fortunately, there have been great advances in the
last decade in identifying the things that need to be included in
climate models (various ocean currents, cloud cover, snow cover,
aerosols, atmospheric makeup, etc), and those models are increasingly
agreeing with the historical and prehistorical record, increasing the
confidence that they are good predictors of future change.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Thu, 08 Mar 2007 17:51:32 -0600, "S. Caro" wrote:

TriMethylAluminum wrote:

Has a small variation such as that been proven to affect global climate as
in the Little Ice Age when
sunspots were non-existent?

Yes..

This link from NASA provides a pretty good layman's explanation about solar
output, what it's thought to do and how it's measured:

http://science.nasa.gov/headlines/y2...jan_solcon.htm

Assuming the original question was about the variability associated with
the 11-year sunspot cycle, the answer is no. What the NASA page is
describing is the effect of much longer cycles in solar activity (the
Sun is a mildly variable star, after all). Those long term cycles appear
to correlate with climatic variation, which is hardly surprising.

To put it differently, we don't observe an 11-year variability in
climate (or even weather).

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

This is a great answer! Thanks. And thanks to all others too.



Has a small variation such as that been proven to affect global climate as
in the Little Ice Age when sunspots were non-existent?

No. The 11-year solar cycle is now included in most climate models, and
doesn't seem to have much if any impact. Similarly, some proxies for
past solar activity (such as carbon-14 in deep ice) don't show much
correlation between short term sunspot activity and climate. In any
case, the 11-year cycle is probably just too short to influence climate.
But there are a number of longer activity cycles, hundreds or even
thousands of years long. Also, the solar constant changes because our
distance from the Sun changes. Basically, you convolve all these cycles-
either intrinsic to the Sun or geometrical, and you get enough variation
in the solar constant to affect climate. This effect is significant in
long term climate models. The solar constant is probably about 0.3%
higher now than it was at the end of the Little Ice Age, 200-300 years
ago. That period may well have correlated with lower solar activity
(although there is nothing that could be called "proof" of that).

The thing that makes all of these models so tricky is that our climate
is metastable. A seemingly small change in something like green house
gas concentration or solar insolation affects other mechanisms,
resulting in relatively short term positive feedback. The end result is
an ice age or a significant rise in temperature, far out of proportion
with the precipitating cause. That could explain why something like the
Maunder minimum, with a solar constant drop of a couple of tenths of a
percent at most could produce such a profound effect, requiring a long
time to recover from. Fortunately, there have been great advances in the
last decade in identifying the things that need to be included in
climate models (various ocean currents, cloud cover, snow cover,
aerosols, atmospheric makeup, etc), and those models are increasingly
agreeing with the historical and prehistorical record, increasing the
confidence that they are good predictors of future change.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

In article ,
Chris L Peterson wrote:

To put it differently, we don't observe an 11-year variability in
climate (or even weather).

We cannot observe an 11-year variability in climate because climate
is, by definition, the weather averaged over 30-year periods! The
current climate is the weather averaged from 1960 to 1989 - the latest
climate period with data available. In 12 years, 1990-2019 will define
the current climate; we're gathering data for that period now.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

Paul Schlyter wrote:
We cannot observe an 11-year variability in climate because climate
is, by definition, the weather averaged over 30-year periods! The
current climate is the weather averaged from 1960 to 1989 - the latest
climate period with data available. In 12 years, 1990-2019 will define
the current climate; we're gathering data for that period now.

Really? Hunh, that's interesting! Why don't they define the climate
as a sliding window, so that the climate for (say) 1998 is the average
of the weather from 1969 to 1998, the climate for 2005 is the average
of the weather from 1976 to 2005, and so forth? Do you have any idea
why they defined it with fixed, non-overlapping windows? A sliding
window makes more sense to me, as it avoids the arbitrary boundaries.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html

Yes Sam, but let's remember it's not really the lack of
Suspots...that's just the visible sign that something is
happening,...it's the lessening of Flares and CME's (generated by
internal mechanisms that we are just now beginning to understand
somewhat) that produces less radiation that's the problem. And
although 1/10 isn't a great number it adds up.

Some months ago, I e-mailed the good folks at SOHO to ask if they
really had seen some change (apart from the general variability of
each cycle) that would account for
Global Warming and they said...NO they had not.

And, if we want to consider the question of Global Warming further
there is Global Dimming which masks the warming effect because of the
increase in particulates in the atmosphere. See PBS NOVA "Global
Dimming" for reference.