What the science says

[ding]

The oxygen isotope curve is well established for the Cenozoic and shows that the trend is for a COOLING earth. Over the last 5 million years there has been rapid cooling.

Climate models predict that extensive glaciation cannot occur at the South Pole until atmospheric CO2 reaches 600 ppm. Climate models predict that extensive glaciation cannot occur at the North Pole until atmospheric CO2 reaches 250 ppm.

Five million years ago the earth started going through glacial / interglacial cycles. The glacial / interglacial cycles of the past 5 million years were triggered by Milankovitch cycles. But before the glacial cycle could be triggered, two conditions needed to be met; the north and south poles had to be isolated from warm marine currents and atmospheric CO2 needed to be 400 ppm or less. These conditions still exist today.

The north pole is isolated by landmasses. The south pole is isolated because of Antarctica.

Trust me... we would be much better off at 600 ppm than we would 250 ppm which is the UN's goal. Luckily for us, we won't get any where close to that in our lifetime.

 

[Crick]

How do you see the Antarctic continent as being isolated from warm ocean currents?

 

[ding]

How do you see the Antarctic continent as being isolated from warm ocean currents?

The pole is isolated from warm marine currents. The Antarctic continent is what is isolating the south pole of the planet from warm marine currents. Basically when the poles become isolated from warm marine currents the threshold is lowered for glaciation at the poles. The south pole has a lower threshold for glaciation than the north pole because a continent is parked over the south pole while the north pole is somewhat less isolated because other land masses are interfering with the circulation of the warm marine currents of the ocean rather than a landmass being parked over the pole.

 

[Crick]

Antarctica and its ice sheets have been responding to warm ocean currents for decades now. What do you think destabilized the West Antarctic Ice Sheet (WAIS)?

 

[ding]

Antarctica and its ice sheets have been responding to warm ocean currents for decades now. What do you think destabilized the West Antarctic Ice Sheet (WAIS)?

Well given that through the geologic record that CO2 has lagged temperature by 800 years, I'm not convinced that CO2 is the driving force in climate change. I see it more as reinforcing climate change. When it heats up more CO2 is released from the ocean, thus reinforcing the temperature change. When it cools down, the oceans absorb more CO2 from the atmosphere, thus reinforcing temperature change. Mind you I'm not arguing that there is no greenhouse gas effect. Of course there is and we should all be glad there is because the earth would be much colder without that effect. The reality is that the majority of the impact is at really really low atmospheric CO2 levels. There is a logarithmic relationship between atmospheric CO2 and associated temperature change. Basically it is diminishing returns. But to answer your question, there are lots of moving parts and it gets really really complicated fast. My personal belief is that the oceans play the biggest role with orbital effects acting as a trigger for climate changes. Water vapor is the dominant GHG and we can't really history match that with past climate changes. As for the ice sheets, we'll know more later because if you know anything about where CO2 is being emitted in the world and why it is being emitted, then you will know that nothing is going to change anytime soon.

 

[IanC]

Antarctica and its ice sheets have been responding to warm ocean currents for decades now. What do you think destabilized the West Antarctic Ice Sheet (WAIS)?

IF, a big if, the WAIS has been destabilized, then it was caused by coming out of the last Ice Age 5000yrs ago. aided by the line of active volcanoes under the west side of the continent.

ice sheets are slow reacting so the last few decades is essentially a single data point in a long history, of which we have no records.

 

[Crick]

That is NOT the opinion of the experts Ian.

Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin
Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin
“Unstoppable” Destabilization of West Antarctic Ice Sheet: Threshold May Have Been Crossed
Antarctic coast meltdown could trigger ice-sheet collapse
http://www.sciencemag.org/news/2015...antarctic-ice-sheet-raise-sea-levels-3-meters

Stability of the West Antarctic ice sheet in a warming world : Nature Geoscience : Nature Research

 

[ding]

That is NOT the opinion of the experts Ian.

If the experts behave anything like you do, then they are not experts.

 

[Crick]

Did you have anything pertinent to add to the conversation? Did you find my comment to Ian offensive in some manner? If so, please report it to management.

 

[ding]

Did you have anything pertinent to add to the conversation? Did you find my comment to Ian offensive in some manner? If so, please report it to management.

Did I have anything pertinent to add to the conversation? Yes, I already added it. Your comments in my thread were unprofessional. Your interpretation of the data was not only wrong it was 180 degrees from being right. The paper you posted was the paper I used and in fact pretty much everyone uses for climate modeling. So when you believed its reference to episodic ice sheets somehow proved that bipolar glaciation had occurred earlier, you totally missed the point of that paper. So, if your experts are anything like you, they are no experts. Now do you understand?

 

[Crick]

What do you understand "episodic Northern-hemispheric ice sheets" through a period in which CO2 was continuously below the Antarctic glaciation threshold to mean?

I quote "Proxy CO2 estimates remain above our model’s northern-hemispheric glaciation threshold of ~280 p.p.m.v. until ~25 Myr ago, but have been near or below that level ever since. This implies that episodic northern-hemispheric ice sheets have been possible some 20 million years earlier than currently assumed (although still much later than Oi-1) and could explain some of the variability in Miocene sea-level records"

Antarctica and its ice sheets have been responding to warm ocean currents for decades now. What do you think destabilized the West Antarctic Ice Sheet (WAIS)?

Well given that through the geologic record that CO2 has lagged temperature by 800 years, I'm not convinced that CO2 is the driving force in climate change. I see it more as reinforcing climate change. When it heats up more CO2 is released from the ocean, thus reinforcing the temperature change. When it cools down, the oceans absorb more CO2 from the atmosphere, thus reinforcing temperature change.

Shakun's work on the early Holocene [http://www.nature.com/nature/journal/v484/n7392/full/nature10915.html]showed that interglacials were initiated by Milankovitch cycles but were reinforced and extended by increased CO2 released from warming oceans and tundra. However, a later paper of his [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.700.4832&rep=rep1&type=pdf] concludes that "The first mode of deglacial climate variability is common to most climate records and is likely related to rising CO2, implicating it as a major deglacial forcing/feedback"

Mind you I'm not arguing that there is no greenhouse gas effect. Of course there is and we should all be glad there is because the earth would be much colder without that effect. The reality is that the majority of the impact is at really really low atmospheric CO2 levels.

That's probably true but has no relevance to anything of concern to humanity at present. We're not going to see "really really low atmospheric CO2 levels" for several centuries at least. Climate sensitivity at it's current range is still approximately 3C/doubling which is sufficient to easily take the Earth's temperature into a very 'expensive' range without significant efforts on all our parts.

There is a logarithmic relationship between atmospheric CO2 and associated temperature change. Basically it is diminishing returns. But to answer your question, there are lots of moving parts and it gets really really complicated fast. My personal belief is that the oceans play the biggest role with orbital effects acting as a trigger for climate changes. Water vapor is the dominant GHG and we can't really history match that with past climate changes. As for the ice sheets, we'll know more later because if you know anything about where CO2 is being emitted in the world and why it is being emitted, then you will know that nothing is going to change anytime soon.

You have not answered the question. What do you believe has destabilized the WAIS?

 

[ding]

What do you understand "episodic Northern-hemispheric ice sheets" through a period in which CO2 was continuously below the Antarctic glaciation threshold to mean?

I quote "Proxy CO2 estimates remain above our model’s northern-hemispheric glaciation threshold of ~280 p.p.m.v. until ~25 Myr ago, but have been near or below that level ever since. This implies that episodic northern-hemispheric ice sheets have been possible some 20 million years earlier than currently assumed (although still much later than Oi-1) and could explain some of the variability in Miocene sea-level records"

Antarctica and its ice sheets have been responding to warm ocean currents for decades now. What do you think destabilized the West Antarctic Ice Sheet (WAIS)?

Well given that through the geologic record that CO2 has lagged temperature by 800 years, I'm not convinced that CO2 is the driving force in climate change. I see it more as reinforcing climate change. When it heats up more CO2 is released from the ocean, thus reinforcing the temperature change. When it cools down, the oceans absorb more CO2 from the atmosphere, thus reinforcing temperature change.

Shakun's work on the early Holocene [http://www.nature.com/nature/journal/v484/n7392/full/nature10915.html]showed that interglacials were initiated by Milankovitch cycles but were reinforced and extended by increased CO2 released from warming oceans and tundra. However, a later paper of his [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.700.4832&rep=rep1&type=pdf] concludes that "The first mode of deglacial climate variability is common to most climate records and is likely related to rising CO2, implicating it as a major deglacial forcing/feedback"

Mind you I'm not arguing that there is no greenhouse gas effect. Of course there is and we should all be glad there is because the earth would be much colder without that effect. The reality is that the majority of the impact is at really really low atmospheric CO2 levels.

That's probably true but has no relevance to anything of concern to humanity at present. We're not going to see "really really low atmospheric CO2 levels" for several centuries at least. Climate sensitivity at it's current range is still approximately 3C/doubling which is sufficient to easily take the Earth's temperature into a very 'expensive' range without significant efforts on all our parts.

There is a logarithmic relationship between atmospheric CO2 and associated temperature change. Basically it is diminishing returns. But to answer your question, there are lots of moving parts and it gets really really complicated fast. My personal belief is that the oceans play the biggest role with orbital effects acting as a trigger for climate changes. Water vapor is the dominant GHG and we can't really history match that with past climate changes. As for the ice sheets, we'll know more later because if you know anything about where CO2 is being emitted in the world and why it is being emitted, then you will know that nothing is going to change anytime soon.

You have not answered the question. What do you believe has destabilized the WAIS?

The paper you referenced established the glaciation threshold for the north pole at ~280 ppm and ~750 ppm for the south pole which was lower than the CO2 values estimated by geochemical proxies10, 11 and carbon-cycle models13, 14. This means there was no glaciation at the north pole until as recently as 500,000 years ago. Prior to that time they found... Instead of bipolar glaciation, we find that Oi-1 is best explained by Antarctic glaciation alone.

 

[ding]

The apparent absence of contemporaneous cooling in deep-sea Mg/Ca records4, 5, 6, however, has been argued to reflect the growth of more ice than can be accommodated on Antarctica; this, combined with new evidence of continental cooling7 and ice-rafted debris8, 9 in the Northern Hemisphere during this period, raises the possibility that Oi-1 represents a precursory bipolar glaciation. Here we test this hypothesis using an isotope-capable global climate/ice-sheet model that accommodates both the long-term decline of Cenozoic atmospheric CO2 levels10, 11 and the effects of orbital forcing12. We show that the CO2 threshold below which glaciation occurs in the Northern Hemisphere (~280 p.p.m.v.) is much lower than that for Antarctica (~750 p.p.m.v.). Therefore, the growth of ice sheets in the Northern Hemisphere immediately following Antarctic glaciation would have required rapid CO2 drawdown within the Oi-1 timeframe, to levels lower than those estimated by geochemical proxies10, 11 and carbon-cycle models13, 14. Instead of bipolar glaciation, we find that Oi-1 is best explained by Antarctic glaciation alone...

Episodic ice sheets are not the same thing as glaciation and are not a part of the geologic record.

 

[ding]

What do you understand "episodic Northern-hemispheric ice sheets" through a period in which CO2 was continuously below the Antarctic glaciation threshold to mean?

I quote "Proxy CO2 estimates remain above our model’s northern-hemispheric glaciation threshold of ~280 p.p.m.v. until ~25 Myr ago, but have been near or below that level ever since. This implies that episodic northern-hemispheric ice sheets have been possible some 20 million years earlier than currently assumed (although still much later than Oi-1) and could explain some of the variability in Miocene sea-level records"

Antarctica and its ice sheets have been responding to warm ocean currents for decades now. What do you think destabilized the West Antarctic Ice Sheet (WAIS)?

Well given that through the geologic record that CO2 has lagged temperature by 800 years, I'm not convinced that CO2 is the driving force in climate change. I see it more as reinforcing climate change. When it heats up more CO2 is released from the ocean, thus reinforcing the temperature change. When it cools down, the oceans absorb more CO2 from the atmosphere, thus reinforcing temperature change.

Shakun's work on the early Holocene [http://www.nature.com/nature/journal/v484/n7392/full/nature10915.html]showed that interglacials were initiated by Milankovitch cycles but were reinforced and extended by increased CO2 released from warming oceans and tundra. However, a later paper of his [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.700.4832&rep=rep1&type=pdf] concludes that "The first mode of deglacial climate variability is common to most climate records and is likely related to rising CO2, implicating it as a major deglacial forcing/feedback"

Mind you I'm not arguing that there is no greenhouse gas effect. Of course there is and we should all be glad there is because the earth would be much colder without that effect. The reality is that the majority of the impact is at really really low atmospheric CO2 levels.

That's probably true but has no relevance to anything of concern to humanity at present. We're not going to see "really really low atmospheric CO2 levels" for several centuries at least. Climate sensitivity at it's current range is still approximately 3C/doubling which is sufficient to easily take the Earth's temperature into a very 'expensive' range without significant efforts on all our parts.

There is a logarithmic relationship between atmospheric CO2 and associated temperature change. Basically it is diminishing returns. But to answer your question, there are lots of moving parts and it gets really really complicated fast. My personal belief is that the oceans play the biggest role with orbital effects acting as a trigger for climate changes. Water vapor is the dominant GHG and we can't really history match that with past climate changes. As for the ice sheets, we'll know more later because if you know anything about where CO2 is being emitted in the world and why it is being emitted, then you will know that nothing is going to change anytime soon.

You have not answered the question. What do you believe has destabilized the WAIS?

For major bipolar glaciation to have occurred at Oi-1, CO2 would first have to cross the Antarctic glaciation threshold (,750 p.p.m.v.) and then fall more than 400 p.p.m.v. within ,200 kyr to reach the Northern Hemisphere threshold (Fig. 4). Increased sea ice and upwelling in the Southern Ocean 13,29 and falling sea level 14 could have acted as feedbacks accelerating CO2 drawdown at the time of Oi-1.This is supported by CO2 proxy records and carbon-cycle model results showing a drop in CO2 across the Eocene/Oligocene transition10,13,14, but none of these reconstructions reach the low levels required for Northern Hemisphere glaciation. We therefore conclude that major bipolar glaciation at the Eocene/Oligocene transition is unlikely, and Mg/Ca-based estimates of deep-sea temperatures across the boundary 5 are unreliable. Our findings lend support to the hypothesis that the 1-km deepening of the carbonate compensation depth and the associated carbonate ion effect on deep-water calcite mask a cooling signal in the Mg/Ca records 4,5. Therefore, the observed isotope shift at Oi-1 is best explained by Antarctic glaciation 22 accompanied by 4.0 uC of cooling in the deep sea or slightly less (,3.3 uC) if there was additional ice growth on West Antarctica (see Methods and Supplementary Information). This explanation is in better agreement with sequence stratigraphic estimates of sea-level fall at Oi-1(70 620 m)19,20 equivalent to 70–120% of modern Antarctic ice volume, and coupled GCM/ice-sheet simulations showing 2–5 uC cooling and expanding sea ice in the Southern Ocean in response to Antarctic glaciation 29. Additional support for ocean cooling is provided by new records from Tanzania 16 and the Gulf of Mexico 15, where Mg/Ca temperature estimates show ,2.5 uC cooling in shallow, continental shelf settings during the first step of the Eocene/Oligocene transition.

In summary, our model results show that the Northern Hemisphere contained glaciers and small, isolated ice caps in high elevations through much of the Cenozoic, especially during favourable orbital periods (Fig. 3a–c). However, major continental-scale Northern Hemisphere glaciation at or before the Oi-1 event (33.6Myr) is unlikely, in keeping with recently published high-resolution Eocene no definitive evidence of widespread northern-hemispheric glaciation exists before ,2.7 Myr ago, pre-Pliocene records from subsequently glaciated high northern latitudes are generally lacking. More highly resolved CO2 records focusing on specific events, along with additional geological information from high northern latitudes, will help to unravel the Cenozoic evolution of the cryosphere. According to these results, this evolution may have included an episodic northern-hemispheric ice component for the past 23 million years.

Thresholds for Cenozoic bipolar glaciation

 

[Crick]

Pick up your microphone and identify current continent-scale glaciation.

 

[ding]

Pick up your microphone and identify current continent-scale glaciation.

You have been proven wrong without a shadow of doubt and you still can't admit that you were wrong?

 

[Crick]

Where do you see continent-scale glaciation in today's Northern Hemisphere? Your attacks on me aren't going to go very far till you answer that one.

 

[ding]

Where do you see continent-scale glaciation in today's Northern Hemisphere?

Bipolar glaciation does exist at present, we are presently in an interglacial cycle, but there are still glaciers in the northern hemisphere today. They just aren't extensive as they are in a glacial cycle. 12,000 years ago the Great Lakes were formed when the glacier retreated. At that time New York was under 1000 ft of ice.

So what if we do not have extensive glaciation in the Northern Hemisphere today. We aren't supposed to, we are in an interglacial cycle. What does that have to do with bi-polar glaciation being rare and possibly unique. Nothing. There are no other known instance of bipolar glaciation recorded in the geologic record.

It is a very good thing we are not in a glacial cycle right now, because it would be very very bad for us if we were. The conditions which led to the glacial-interglacial cycles of the last 5 million years still exists today.

Your latest argument is that because we are not in a glacial cycle today, then my point that bi-polar glaciation being rare and possibly unique doesn't matter. That is a stupid argument. The best way to understand future climate change is to study past climate change. So, yes, it really does matter.

 

[ding]

Your attacks on me aren't going to go very far till you answer that one.

You think I am attacking you? I am exposing your incompetence and dishonesty. That's not an attack.

 

[Crick]

Where do you see continent-scale glaciation in today's Northern Hemisphere?

Bipolar glaciation does exist at present, we are presently in an interglacial cycle, but there are still glaciers in the northern hemisphere today. They just aren't extensive as they are in a glacial cycle. 12,000 years ago the Great Lakes were formed when the glacier retreated. At that time New York was under 1000 ft of ice.

Why don't you try one more time and answer what I actually asked you.