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Why the Sun seems to be 'dimming'

Posted by: Sigurd - Thu Jan 13, 2005 5:48 pm
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Why the Sun seems to be 'dimming' 
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Post    Posted on: Tue Jan 18, 2005 8:04 am
Good link, nice read. Thanks luke.

DKH

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Post    Posted on: Thu Jan 20, 2005 8:45 am
Anybody seen the BBC Horizon documentary about this global dimming? It's queit shocking to be honest.


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Post    Posted on: Tue Jan 25, 2005 2:39 pm
Stefan wrote:
Anybody seen the BBC Horizon documentary about this global dimming? It's queit shocking to be honest.


I haven't seen it...


Alan Boyle comments on 2 new environment articles:
http://www.msnbc.msn.com/id/6863460/#050124a

If it's true.. that we where going into an Ice Age.. it will be terrible if when go "out" of it..

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Post    Posted on: Tue Jan 25, 2005 3:52 pm
I thought you could get BBC TV in the BeNeLux? They do in Southern Ireland further South than Dublin...or have you got a different TV system to PAL like Never The Same Colour? :lol:

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Post    Posted on: Tue Jan 25, 2005 4:29 pm
I've downloaded it from the newsgroups ;)

From the documentary its said that the heating will continue even greater, so the ice age will only come if the movie the day after tomorrow is true :)


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Post    Posted on: Tue Jan 25, 2005 4:51 pm
luke.r wrote:
I thought you could get BBC TV in the BeNeLux? They do in Southern Ireland further South than Dublin...or have you got a different TV system to PAL like Never The Same Colour? :lol:


We do have BBC BBC2 etc etc... I guess it's the same for whole western europ.

Stefan wrote:
I've downloaded it from the newsgroups ;)

From the documentary its said that the heating will continue even greater, so the ice age will only come if the movie the day after tomorrow is true :)


If we have to believe the second article, Alan Boyle is commenting on, we're now in an ice age, but no temperature diffrence because of human changes... so if it goes out of the ice age.. we may get a very hot climate.

I think there will be no "real" ice age ;), but the day after tomorrow was just a great movie :)

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Post    Posted on: Tue Jan 25, 2005 9:07 pm
(EDIT) I just looked up the article and have corrected some factual errors here.)

This thread reminds me of an interesting article in the October 2002 issue of Sky and Telescope.

Stellar evolution models show the Sun was 30% less luminous 4.6 Billion years ago. It has been slowly warming and will continue to do so in the coming millennia. At the same time geological data and planetary evolution models say that there was far more CO2 in Earth’s atmosphere in the distant past. The Gaia Hypothesis says that the complex life-Earth system has been actively maintaining a nice temperature for the planet all this time be steadily reducing CO2 concentrations in the atmosphere. The trouble is that almost all the CO2 is gone now. We are down to a few hundred parts per million. At the rate the Sun is warming, it would have to go to zero in “only” a few hundred million years to keep this balance. After that, the Earth just gets hotter and hotter until it is more like Venus. So manmade global warming is just speeding things up by a little bit on the geologic time scale.

But wait!

They also proposed a high tech solution. Very high tech. Change the Earth’s orbit! If Earth’s orbit could be gradually moved farther from the Sun at just the right rate, it could keep pace with Solar warming and maintain our climate! How could we do this? If we redirected a 150 km asteroid into the correct trajectory, it would do a gravity assist pass by the Earth. The asteroid is thrown into a much lower orbit and the Earth is thrown into a slightly higher orbit. The estimate is this would need to be done once every 6,000 years to keep the Earth’s orbit at the right distance from the Sun. Most of the energy to move the asteroid would come from gravitational purturbations by other planets, we would only have to give it a small push in the right direction.

Naturally, this is even more difficult and fraught with political repercussions than greenhouse gas emission controls. Did the engineers make a mistake and accidentally crash the asteroid into the Earth? Do countries in hot climates argue for moving the Earth this millennium and countries in cold climates argue for doing it later? Do some people think we can ignore green house gas emissions and just move the Earth instead? A real political and technological nightmare there. Our civilization will need to grow up and start acting like an adult if we are to survive for the long term! But at least we are not totally doomed. Until the Sun becomes a red giant of course. Then we are in REAL trouble.


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Post    Posted on: Wed Jan 26, 2005 9:50 am
campbelp2002 wrote:
Naturally, this is even more difficult and fraught with political repercussions than greenhouse gas emission controls. Did the engineers make a mistake and accidentally crash the asteroid into the Earth? Do countries in hot climates argue for moving the Earth this millennium and countries in cold climates argue for doing it later? Do some people think we can ignore green house gas emissions and just move the Earth instead? A real political and technological nightmare there. Our civilization will need to grow up and start acting like an adult if we are to survive for the long term! But at least we are not totally doomed. Until the Sun becomes a red giant of course. Then we are in REAL trouble.

I read the same stuff quite recently, it really is an eye-brow raising idea. I didn't think that the proposers were thinking about greenhouse gases at all though, they were just looking at the sun getting bigger over a very long period of time. So I think it's a bit unfair to suggest their idea was a response to greenhouse gas-driven global warming, rather they were thinking of the "swelling-sun"-driven globabl warming problem. The other thing is that we can predict with reasonable accuracy the position of NEARs over decades of time, it would be very suprising if these engineers of the future bump their rock into the planet by accident. So I think your warnings are little over the top.

Furthermore, to be honest, from the perspective of a species "swelling-sun"-driven global warming might not actually be a problem. It would be surprising if humans will still be around in a billion years. Name a species in the chordate phyla that has survived for a billion years. Sorry, that's a rough ask, we haven't even had chordate's for a billion years yet.

Those guys were just thinking of a "really cool idea" with no sensibly practical purpose.

DKH

(poo poo I say)

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Post    Posted on: Wed Jan 26, 2005 1:55 pm
Actually the political problems were my own idea. The only problem the article posed was accidentally hitting Earth.
But I agree, it is not really a serious proposal to do something.


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Post    Posted on: Wed Jan 26, 2005 4:20 pm
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Furthermore, to be honest, from the perspective of a species "swelling-sun"-driven global warming might not actually be a problem. It would be surprising if humans will still be around in a billion years.


At our current rate of progress, we might just about have clawed our way out as far as the Jovian moons with manned missions. Is that far enough? Will we still be human in the sense we know in a billion years or does our technology stifle physical evolution? There are too many variables over these kind of time-scales...
I'm off to ponder them over a lovely warm thick beer! :lol:

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Post    Posted on: Thu Jan 27, 2005 3:22 am
http://news.bbc.co.uk/2/hi/science/nature/4210629.stm

Alarm at new climate warning

A "VERY" good article!

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Post    Posted on: Thu Jan 27, 2005 5:13 pm
The article says that there is "no such thing as a safe level of carbon dioxide".
That is an unnecessarily alarming and technically false claim. The 200-300 ppm level that pervaled before the industrial revolution is the safe level. If we were to somehow reduce it to zero then all green plants in the world would die from lack of CO2.


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Post    Posted on: Sun Jan 30, 2005 4:29 am
campbelp2002 wrote:
The article says that there is "no such thing as a safe level of carbon dioxide".
That is an unnecessarily alarming and technically false claim. The 200-300 ppm level that pervaled before the industrial revolution is the safe level. If we were to somehow reduce it to zero then all green plants in the world would die from lack of CO2.


I think you're the one acting simplistic while writing that reply, it's not a false claim at all.
I guess you DO understand that 400 ppm is dangerous, cause it will create a large temperature diffrence.
And that +- 300 pm would be good in our "current situation" to have no temperature diffrences etc.. with other words, to stop the PPM form "going up".

No one was talking about putting it to 0, except you, who clearly didn't understood their sentence (haven't you studied math and science at school ?)
With talking about, there is no such thing as a safe level, is that there can't be 1 red line... we'll survive when we have 400 pm... but a lot more difficult... 300 would be a lot better for us... that's what they ment to say.
That we have to decide ourself, and if we lower it.. it may also affect other things, so they say it's "complex", not something as black and white.
I guess you read it in a very simplistic way, as if you understood it as "if there is no safe level, then we shouldn't have it at all", no, if there is no safe level.. then we have to chose a level, causing "no" harm, but there will be no "perfect" level to chose from.

An other new article released by the BBC:
http://news.bbc.co.uk/2/hi/uk_news/engl ... 218441.stm

And I do think those latest articles are "serious".

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Post    Posted on: Sun Jan 30, 2005 3:19 pm
http://www.climateprediction.net/science/pubs/nature_first_results.pdf

these are the preliminary results for the boinc project dedicated to predicting the long term effects of an increased CO2 content on climate. basically they say that doubling CO2 levels will raise global mean temperature by 2-11K over 15 years, which is more than previously thought. the article is scientific and very hard to read, but there's a summary on the front page if you don't feel like wading through it.

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Post    Posted on: Sun Jan 30, 2005 8:19 pm
interesting topic... think of the consequences of a 10C rise... not only would parts of the world be uninhabitable completely, but hurricane/monsoon season would be year round... And Florida suffered BILLIONS in damages from 4 this year, having to go through that continuously would literally cause Florida to be buried under the ocean...

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