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Post by sigurdur on Feb 16, 2013 3:33:01 GMT
Contentious observations of Pleistocene shoreline features on the tectonically stable islands of Bermuda and the Bahamas have suggested that sea level about 400,000 years ago was more than 20 metres higher than it is today1, 2, 3, 4. Geochronologic and geomorphic evidence indicates that these features formed during interglacial marine isotope stage (MIS) 11, an unusually long interval of warmth during the ice age www.nature.com/nature/journal/v483/n7390/full/nature10891.html |
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Post by sigurdur on Feb 16, 2013 3:49:42 GMT
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Post by sigurdur on Feb 16, 2013 4:03:50 GMT
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Post by karlox on Feb 16, 2013 19:36:47 GMT
From linked paper: quote Some climate models suggest that because of the current unique orbital geometry, earth won’t shift into an Ice Age again for another 40,000 years. The models predict a complete melting of the northern Ice Cap 30,000 years in the future, but if modern anthropogenic factors are considered, the northern Ice Cap will collapse in less than 200 years unquote 30000 years versus 200 seems quite an important impact. |
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Post by nautonnier on Feb 16, 2013 22:46:21 GMT
From linked paper: quote Some climate models suggest that because of the current unique orbital geometry, earth won’t shift into an Ice Age again for another 40,000 years. The models predict a complete melting of the northern Ice Cap 30,000 years in the future, but if modern anthropogenic factors are considered, the northern Ice Cap will collapse in less than 200 years unquote 30000 years versus 200 seems quite an important impact. It would be an important impact if it is true. So the chaotic climate system is orbiting the current interglacial attractor. Sometimes it is close to the attractor and very little would make it change state to another. Other times it is right on the boundary and a correctly timed input may cause it to flip into another state. (This after all is what the warmists are claiming for CO2). However, let's take Svensmark's hypothesis and say that it is GCR that may vary in numbers with solar wind but also vary due to the effects of supernovae that occured eons ago. Whereas there is zero empirical evidence for the impact of CO2 on climate there is significant evidence for GCR impact. Both from CERN and from the timing of supernovae and climate changes. I think people who believe that Milankovitch cycles are the sole drivers of glacials and interglacials are being a little simplistic |
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Post by nonentropic on Feb 16, 2013 23:17:10 GMT
Naut you are correct.
In fact the likelihood of the arctic melt being driven by CO2 rather than say carbon emissions/deposition is highly suspect given the extent of the winter low solar radiation period recovery and the fact that the antarctic, which is largely isolated from the industrial filth does not look to be under thermal stress at all.
it would seem a massive advantage to the world if this were in fact the case.
By pushing the Chinese and all others to substitute coal with gas this world would not only allow us to discover if carbon is the evil but it would reduce the CO2 emissions by 50%, a good start.
wind farms belong in Parliament and the UN near the source of the energy.
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Post by sigurdur on Feb 17, 2013 0:14:29 GMT
:"wind farms belong in Parliament and the UN near the source of the energy."
Great observation nonentropic
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Post by sigurdur on Feb 17, 2013 0:16:52 GMT
From linked paper: quote Some climate models suggest that because of the current unique orbital geometry, earth won’t shift into an Ice Age again for another 40,000 years. The models predict a complete melting of the northern Ice Cap 30,000 years in the future, but if modern anthropogenic factors are considered, the northern Ice Cap will collapse in less than 200 years unquote 30000 years versus 200 seems quite an important impact. Karlox: Before you started observing this blog, there was a fellow named William who posted often about magnetic influence on climate. The Milankovich cycles have correlation. But if you examine MIS-5,7,9 and 11, you will see that correlation does not mean causation. There are many questions, yet unanswered, about Milankovich cycles and climate. |
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Post by karlox on Feb 17, 2013 10:52:21 GMT
From linked paper: quote Some climate models suggest that because of the current unique orbital geometry, earth won’t shift into an Ice Age again for another 40,000 years. The models predict a complete melting of the northern Ice Cap 30,000 years in the future, but if modern anthropogenic factors are considered, the northern Ice Cap will collapse in less than 200 years unquote 30000 years versus 200 seems quite an important impact. Karlox: Before you started observing this blog, there was a fellow named William who posted often about magnetic influence on climate. The Milankovich cycles have correlation. But if you examine MIS-5,7,9 and 11, you will see that correlation does not mean causation. There are many questions, yet unanswered, about Milankovich cycles and climate. Sigurdur, my intuition -not my knowledge- tells me that a good graphical similarity of climate understanding complexity could be obtained just watching sea tides over tides and waves over waves and trying to figure it out mathematically all forces and signals involved so as to understand why a given water particle is to be placed at a given 3D coordinates or nearby... You can see how waves and ripples of different lenght and frequencies interact, plus tide rising or falling at a time, plus winds blowing or not... We are learning, but have a long way ahead before being able to predict eactly where our ´water molecule´ will be placed within a few hours, or 20 years for an accurate global weather-climatic trend prediction. Fractal maths and chaotic structures involved... but we should be able to detect more accurately decadal trends once we understand major forces involved, don´t think we are far from that (though a seasonal forecast migh fail because we haven´t reach that model or level of´resolution´ yet. |
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Post by steve on Feb 17, 2013 11:25:53 GMT
I think people who think there are serious people who believe that Milankovitch cycles are the sole drivers of glacials and interglacials are being a little simplistic, are being a little simplistic.
People who put forward such claims in support of an alternative theory with close to zero empirical evidence are being misleading.
The Milankovitch theory does not need to be perfect to be compelling. We know the theory is based on very subtle changes in the distribution (not the amount) of solar irradiation through the days and seasons, so equally subtle changes on similar timescales could derail it (such as changes in the land masses leading to changes in vegetation or ocean currents).
We are not even close to being able to model (yes model!) the trajectory of the sun and stars in the galaxy to be in any position to test the cosmic theories, nor do the cosmic theories offer any compelling empirical evidence based on existing observations or theory.
I think it is safe to say that since the Greenland icecap expanded in response to the recent (last few thousand years) reduction in summer sunshine (related to Milankovitch cycles) there is a good chance that Greenland and West Antarctica will retreat due to the significant higher level of global warming caused by the CO2 rise.
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Post by nautonnier on Feb 17, 2013 12:58:58 GMT
"I think it is safe to say that since the Greenland icecap expanded in response to the recent (last few thousand years) reduction in summer sunshine (related to Milankovitch cycles) there is a good chance that Greenland and West Antarctica will retreat due to the significant higher level of global warming caused by the CO2 rise."Hi Steve - you do know that there is a challenge out for someone to provide empirical evidence that CO 2 causes any rise in atmospheric temperature don't you. You could really make a name for yourself if you can provide that evidence. We are talking Nobel prize level name for yourself. So far no-one has been able to do so. Milankvitch cycle hypothesis is based on the slow and small change in the earth's orbit leading to a reduction in solar energy which in turn drives the ice ages. It probably has some effect, but if it were the sole effect then people studying orbital mechanics would be able to forecast and hindcast extremely precisely the times of glaciation. They cannot - the Milankovitch does it all on its own hypothesis is too simplistic. Therefore, there is something else influencing the glaciation. The best hypothesis so far is from Svensmark www.ras.org.uk/news-and-press/219-news-2012/2117-did-exploding-stars-help-life-on-earth-to-thrive Perhaps you have reviewed it and found the glaring error in Svensmark's hypothesis that others have missed? Again, a short paper showing up Svensmark's errors would really put you up there in Nobel territory. If glaciations were extremely simple to explain if it were Milankovitch cycles modified by CO 2 then people would have stopped worrying about whether there is an ice age around the corner. But they are not simple to explain - entry and exit to glacials is not mechanistically linked to Milankovitch cycles, and CO 2 levels do not appear to have any link either apart from a several century long lag in rise after entry into an interglacial and a lag in a drop of concentrations after the entry into a glacial. But again - surprise everyone steve 
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Post by steve on Feb 17, 2013 14:05:22 GMT
nautonnier, you are repeating yourself. Lined up against each other, the Milankovitch theory is plausible, has observational evidence and shows some good correlations. The Svensmark theory has a couple of extreme Forbush events *possibly* linked to changes in some clouds. The Milankovitch theory has subtle impacts that mean that the feedbacks (such as the retreat of ice sheets changing the albedo and causing more warming and more retreat) are subtle and not predictable.
Saying one theory is a bit rubbish and cannot explain everything, so therefore the next best (massively more rubbish theory) must be true is demonstrating fake scepticism.
PS. You don't win Nobel prizes for pointing out the many flaws in a speculative and poorly developed hypothesis such as Svensmark's.
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Post by sigurdur on Feb 17, 2013 15:33:08 GMT
Steve:
The thing that must be understood is that Milankovitch theory looks good, but does have several items of question.
So does Svensmark's.
What this shows us is that there are "loose ends" that need to be taken care off in our understanding of climate and what causes changes.
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Post by nautonnier on Feb 17, 2013 17:36:48 GMT
nautonnier, you are repeating yourself. Lined up against each other, the Milankovitch theory is plausible, has observational evidence and shows some good correlations. The Svensmark theory has a couple of extreme Forbush events *possibly* linked to changes in some clouds. The Milankovitch theory has subtle impacts that mean that the feedbacks (such as the retreat of ice sheets changing the albedo and causing more warming and more retreat) are subtle and not predictable. Saying one theory is a bit rubbish and cannot explain everything, so therefore the next best (massively more rubbish theory) must be true is demonstrating fake scepticism. PS. You don't win Nobel prizes for pointing out the many flaws in a speculative and poorly developed hypothesis such as Svensmark's. I cannot see the word 'rubbish' in my comment - it was 'simplistic'. And I repeat that if Milankovitch was correct then mechanistically forecasting and hindcasting glacials and interglacials would be the stuff of undergraduate science. It does not appear to correlate in that way. That is not to say there is no effect - as I said in my original post there are times when the climate system is at the extreme of its cycle around an attractor but it is obviously not the sole reason for switching between glacial and interglacial. Something else happens that changes the state of the climate that then after that change moves into the opposite state. Timing shows that CO 2 lags not leads. Therefore, look for other effects. I don't believe that you have read Svensmark's theory if you believe your strawman that all Svensmark is discussing is Forbush events which are solar CME related and not supernova sourced GCR related. There is more to the paper than 'only' glacial/interglacial and far more compelling evidence. Try reading the summary here 'again' www.ras.org.uk/news-and-press/219-news-2012/2117-did-exploding-stars-help-life-on-earth-to-thrive Its only a page long summary. There are also papers by Nir Shaviv covering similar areas. |
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Post by nonentropic on Feb 17, 2013 19:06:18 GMT
One of the biggest drives of mankind is the search for routine.
Its the step below control, that is prediction.
The problem is that any phenomena such as climate, which depends on hundreds of variables whether they be cyclical or not can only be predicted if there are some very large variable or variables in there.
By way of example the tide is a good example inside my bay at home here it's the big sea level driver, go outside my bay in a storm and it's a small part of the instantaneous sea level.
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