Re: Study acquits sun of climate change


<mrdarrett@xxxxxxxxx> wrote in message
news:1158346727.981928.250710@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
http://www.cnn.com/2006/TECH/science/09/15/global.warming.sun.reut/index.html

"Researchers from Germany, Switzerland and the United States found that
the sun's brightness varied by only 0.07 percent over 11-year sunspot
cycles, far too little to account for the rise in temperatures since
the Industrial Revolution."

Towards the end of the article:

"And global Ice Ages, like the last one which ended about 10,000 years
ago, seem linked to cyclical shifts in the earth's orbit around the sun
rather than to changes in solar output."

So... tell us more about those shifts in the earth's orbit around the
sun. Could these shifts also be acquitted of current (last hundred
years') climate change?



On another note:

http://en.wikipedia.org/wiki/Axial_tilt

"The Earth's axial tilt varies between 22.1° and 24.5° (but see
below), with a 41,000-year periodicity, and at present, the tilt is
decreasing. In addition to this steady decrease, there are also much
smaller short term (18.6 years) variations, known as nutation."

Tell us more! I'm guessing a decrease in tilt should actually cause
cooling... am I right?

Michael


Ok.. It's not quite that simple, but simple enough.

First of all, the Earth has to radiate all the energy from the day
side back into space on the night side, which it does, or it
would rapidly heat up.

Secondly, Antarctica, Greenland and **clouds** are white.
White is more reflective than other colours.
You'll notice less direct heat when the sun is hidden by cloud than
when it isn't. Heating the ocean causes evaporation, that
produces cloud and cloud prevents heating the ocean. But the
clouds drift over land, and having drifted out of the way the sun
evaporates more water. Cloud reflects heat back into space.
Rain and snow is the removal of cloud, but snow reflects heat from
the sun back into space, rain does not. So basically the overall
temperature is self-regulating. Too hot, more cloud. Too cool,
less cloud. There is a lot of cloud:
http://www.solarviews.com/raw/earth/earthafr.jpg

=======================================
IMPORTANT.

We call that negative feedback. It tends to stabilise,
but it doesn't prevent slight heating and cooling.

Snow on the ground, however, has the opposite effect.
The more snow there is, the greater the reflection of heat
back into space and the cooler the Earth is, and if the average
temperature is low enough the snow doesn't melt.
On the other hand if all the snow melts, then it doesn't reflect
heat into space and the Earth heats up, so less snow.
We call that positive feedback, it reinforces the cooling or heating.
So it is important that we have the right amount of snow as
well as cloud.
=======================================

Thirdly: the Earth's orbit is elliptical. That means the Earth gets
closer to the sun at perihelion and further from the sun at periastron,
and when it is closer to the sun it is going to get more heat,
less heat when further from the sun, by the inverse square law.
http://www.androcles01.pwp.blueyonder.co.uk/Algol/Eccentric.gif
The cloud cycle will regulate this, more cloud when closer to the
sun, less when further.

Fourthly, the Earth is tilted. This where ice ages come into
the picture. The Earth isn't just tilted, it is a gyroscope, and
like any gyroscope that is pulled by gravity, it precesses.
http://www.gyroscopes.org/images/misc/precess.gif

The Moon is a source of gravity that will make the Earth precess.
One full turn of precession takes about 25,000-27,000 years,
we are not sure of the exact figure.
So....at some point during that 25,000 year period, Antarctica
will be tilted toward the Sun (Southern summer) while at
peristron, and then 12,500 years later, Antartica will be
tilted away from the Sun (Southern winter) at periastron.
the result is that ice formed over the North polar ice cap to
a depth of 2 miles, sea levels dropped 300 feet and we
were in the grip of an ice age. This was not the calamity
you might imagine, animals and man lived comfortably
in what is now the Sahara desert, lush with forests and
rainfall. They just weren't doing quite so well in New York
City, London or Moscow, under the ice.


Fifthly, look again at that gyroscope. It is very much
like the Earth going around a barycentre it shares with the moon.
http://www.androcles01.pwp.blueyonder.co.uk/Algol/Barycentre.gif

It has a constant tilt. If you change the tilt then the gyroscope
would rise and fall rather like a wooden horse on a merry-go-round.
Summers would be shorter or longer as the tilt changed, and
that will affect the duration of the ice age.

Lastly: 11,500 years ago the last ice age ended, the wooly mammoth
died out, the Earth will continue to get warmer for the next 2000 years,
sea levels will continue to rise, there isn't a darn thing we can do
about it and we are not the cause, although we probably killed
off the wooly mammoth for food and some grandmother wrote a
a children's story about a guy called Noah building a farm on a boat to
save all the animals, because that world wide flood really did happen
even if the peoples of the middle East did not know its cause.
Children love fiction, we are scientists, I am not searching Turkey
for the remains of an ark.

After that it will cool again, and we still have no control and are not
responsible. All we can do is what we as a species have always done.
Migrate. There is just no need to in a lifetime, but for the long term we
always have.

As to "Researchers from Germany, Switzerland and the United States"
looking at sunspots, that's like turning on a light in the kitchen
to see if it caused the dishes to be washed, and all that is really
going to happen when I do it is a vodka and coke will arrive at
my desk. The dishes can wait until tomorrow, the light doesn't
have a darned thing to do with it and neither do sunspots. I have
no praise for "Researchers from Germany, Switzerland and the
United States" looking at sunspots and saying it was NOT the cause.

Androcles





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