The modern icehouse world we live in is geologically rare

[ding]

The world we live in today is an icehouse world. It is characterized by bipolar glaciation.

We think of this as normal, but it's not. For most of the past 55 million years our planet was a greenhouse world.

Bipolar glaciation is geologically rare, possibly unique. No other previous instance of bipolar glaciation has been recorded in the geologic record.

The icehouse world we live in today is characterized by glacial - interglacial cycles and a high latitudinal thermal gradient.

The modern icehouse world we live in today differed strongly from the greenhouse world in that the greenhouse world did not have bipolar glaciation and had a low latitude thermal gradient.

 

[miketx]

 

[ding]

West Alabama Greenhouse

 

[Crick]

I believe this [http://www.nature.com/nature/journal/v455/n7213/full/nature07337.html] says you're full of shit.

 

[ding]

...says you're full of shit.

Good thing you aren't taking this personal. I didn't see anything in your link that refuted what I posted.

How did your link say these things were full of shit?

That the icehouse world we live in today is not normal.

The icehouse world we live in today is characterized by glacial - interglacial cycles and a high latitudinal thermal gradient.

That for most of the last 55 million years our planet was a greenhouse world

That Bipolar glaciation is geologically rare, possibly unique.

That no other previous instance of bipolar glaciation has been recorded in the geologic record.

The modern icehouse world we live in today differed strongly from the greenhouse world in that the greenhouse world did not have bipolar glaciation and had a low latitude thermal gradient.

 

[Crick]

Nature 455, 652-656 (2 October 2008) | doi:10.1038/nature07337; Received 3 April 2008; Accepted 12 August 2008

Thresholds for Cenozoic bipolar glaciation
Robert M. DeConto1, David Pollard2, Paul A. Wilson3, Heiko Pälike3, Caroline H. Lear4 & Mark Pagani5

1. Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
2. Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK
4. School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK
5. Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA

Correspondence to: Robert M. DeConto1 Correspondence and requests for materials should be addressed to R.M.D. (Email: [email protected]).



Top of page
Abstract
The long-standing view of Earth’s Cenozoic glacial history calls for the first continental-scale glaciation of Antarctica in the earliest Oligocene epoch (~33.6 million years ago1), followed by the onset of northern-hemispheric glacial cycles in the late Pliocene epoch, about 31 million years later2. The pivotal early Oligocene event is characterized by a rapid shift of 1.5 parts per thousand in deep-sea benthic oxygen-isotope values3 (Oi-1) within a few hundred thousand years4, reflecting a combination of terrestrial ice growth and deep-sea cooling. 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, combined with deep-sea cooling of up to 4 °C and Antarctic ice that is less isotopically depleted (-30 to -35‰) than previously suggested15, 16. 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 since10, 11. 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 records17, 18.

1. Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
2. Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK
4. School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK
5. Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA

Correspondence to: Robert M. DeConto1 Correspondence and requests for materials should be addressed to R.M.D. (Email: [email protected]).

 

[ding]

Nature 455, 652-656 (2 October 2008) | doi:10.1038/nature07337; Received 3 April 2008; Accepted 12 August 2008

Thresholds for Cenozoic bipolar glaciation
Robert M. DeConto1, David Pollard2, Paul A. Wilson3, Heiko Pälike3, Caroline H. Lear4 & Mark Pagani5

1. Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
2. Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK
4. School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK
5. Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA

Correspondence to: Robert M. DeConto1 Correspondence and requests for materials should be addressed to R.M.D. (Email: [email protected]).



Top of page
Abstract
The long-standing view of Earth’s Cenozoic glacial history calls for the first continental-scale glaciation of Antarctica in the earliest Oligocene epoch (~33.6 million years ago1), followed by the onset of northern-hemispheric glacial cycles in the late Pliocene epoch, about 31 million years later2. The pivotal early Oligocene event is characterized by a rapid shift of 1.5 parts per thousand in deep-sea benthic oxygen-isotope values3 (Oi-1) within a few hundred thousand years4, reflecting a combination of terrestrial ice growth and deep-sea cooling. 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, combined with deep-sea cooling of up to 4 °C and Antarctic ice that is less isotopically depleted (-30 to -35‰) than previously suggested15, 16. 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 since10, 11. 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 records17, 18.

1. Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
2. Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK
4. School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK
5. Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA

Correspondence to: Robert M. DeConto1 Correspondence and requests for materials should be addressed to R.M.D. (Email: [email protected]).

I see.. Can you go down my list and tell me what you believe this refutes? That way we can isolate the disagreement. How's that?


That the icehouse world we live in today is not normal.

The icehouse world we live in today is characterized by glacial - interglacial cycles and a high latitudinal thermal gradient.

That for most of the last 55 million years our planet was a greenhouse world

That Bipolar glaciation is geologically rare, possibly unique.

That no other previous instance of bipolar glaciation has been recorded in the geologic record.

The modern icehouse world we live in today differed strongly from the greenhouse world in that the greenhouse world did not have bipolar glaciation and had a low latitude thermal gradient.

 

[Crick]

Do you actually have this much trouble reading? The article refutes your contention that bipolar glaciation is "rare, possibly unique". You have not defined "icehouse world" or "greenhouse world" nor have you stated what you believe to be the significance of your contention.

 

[ding]

Do you actually have this much trouble reading? The article refutes your contention that bipolar glaciation is "rare, possibly unique". You have not defined "icehouse world" or "greenhouse world" nor have you stated what you believe to be the significance of your contention.

I don't have a problem reading I am having a problem getting you to acknowledge what you accept so that I can then destroy your argument against what you reject using your own link. This papers proves what I said. This is the paper I have relied upon. But first things first, let's identify what you agree with, ok?

For the record, I did characterize icehouse world and greenhouse world. Surely you are intelligent enough about this subject that you know what it means when someone says icehouse worlds and greenhouse worlds, right? Please tell me that you are not so lacking in knowledge of climate science that these are foreign concepts to you.

So do you accept the following?

That the icehouse world we live in today is not normal.

The icehouse world we live in today is characterized by glacial - interglacial cycles and a high latitudinal thermal gradient.

That for most of the last 55 million years our planet was a greenhouse world

The modern icehouse world we live in today differed strongly from the greenhouse world in that the greenhouse world did not have bipolar glaciation and had a low latitude thermal gradient.

 

[ding]

Do you actually have this much trouble reading? The article refutes your contention that bipolar glaciation is "rare, possibly unique". You have not defined "icehouse world" or "greenhouse world" nor have you stated what you believe to be the significance of your contention.

Look if you really want to quibble over these self evident facts that absolutely no one disputes, it will only show how weak you believe your position really is in the first place. I'm good either way.

So do you accept the following?

That the icehouse world we live in today is not normal.

The icehouse world we live in today is characterized by glacial - interglacial cycles and a high latitudinal thermal gradient.

That for most of the last 55 million years our planet was a greenhouse world

The modern icehouse world we live in today differed strongly from the greenhouse world in that the greenhouse world did not have bipolar glaciation and had a low latitude thermal gradient.

 

[ding]

Do you actually have this much trouble reading? The article refutes your contention that bipolar glaciation is "rare, possibly unique". You have not defined "icehouse world" or "greenhouse world" nor have you stated what you believe to be the significance of your contention.

Are you ready for me to expose your trouble with reading?

Are you ready for me to expose your incompetence regarding bipolar glaciation?

Are you ready for me to show you what that paper you posted really said?

Are you ready for me to show you how you were wrong and I was right?

Come on... say it with me...

Bipolar glaciation is geologically rare, possibly unique.

No other previous instance of bipolar glaciation has been recorded in the geologic record.

 

[ding]

Do you actually have this much trouble reading? The article refutes your contention that bipolar glaciation is "rare, possibly unique". You have not defined "icehouse world" or "greenhouse world" nor have you stated what you believe to be the significance of your contention.

Look... you have two choices here, you can admit your mistake and behave professionally now and in the future, or you can be dishonest and try to squirm your way out of this. If you choose the first option I will treat you with the same respect even if I don't always agree with you. If you choose the second option, I will mercilessly expose your dishonesty and everything you do from hereafter will be discredited. I'll make sure of that. The choice is yours. Choose wisely.

 

[ding]

the significance of your contention.

The significance of this thread is to lay the foundation for understanding past climate changes. The best way to understand future climates is to study past climates. According to Raymond S. Bradley, Climatologist and University Distinguished Professor in the Department of Geosciences at the University of Massachusetts Amherst "to anticipate future changes, we must understand how and why climates varied in the past."

 

[Crick]

Do you actually have this much trouble reading? The article refutes your contention that bipolar glaciation is "rare, possibly unique". You have not defined "icehouse world" or "greenhouse world" nor have you stated what you believe to be the significance of your contention.

Look... you have two choices here, you can admit your mistake and behave professionally now and in the future, or you can be dishonest and try to squirm your way out of this. If you choose the first option I will treat you with the same respect even if I don't always agree with you. If you choose the second option, I will mercilessly expose your dishonesty and everything you do from hereafter will be discredited. I'll make sure of that. The choice is yours. Choose wisely.

Do whatever the fuck you want little boy.

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 since10, 11. This implies that episodic northern-hemispheric ice sheets have been possible some 20 million years earlier than currently assumed

 

[ding]

Nature 455, 652-656 (2 October 2008) | doi:10.1038/nature07337; Received 3 April 2008; Accepted 12 August 2008

Thresholds for Cenozoic bipolar glaciation
Robert M. DeConto1, David Pollard2, Paul A. Wilson3, Heiko Pälike3, Caroline H. Lear4 & Mark Pagani5

1. Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
2. Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK
4. School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK
5. Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA

Correspondence to: Robert M. DeConto1 Correspondence and requests for materials should be addressed to R.M.D. (Email: [email protected]).



Top of page
Abstract
The long-standing view of Earth’s Cenozoic glacial history calls for the first continental-scale glaciation of Antarctica in the earliest Oligocene epoch (~33.6 million years ago1), followed by the onset of northern-hemispheric glacial cycles in the late Pliocene epoch, about 31 million years later2. The pivotal early Oligocene event is characterized by a rapid shift of 1.5 parts per thousand in deep-sea benthic oxygen-isotope values3 (Oi-1) within a few hundred thousand years4, reflecting a combination of terrestrial ice growth and deep-sea cooling. 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, combined with deep-sea cooling of up to 4 °C and Antarctic ice that is less isotopically depleted (-30 to -35‰) than previously suggested15, 16. 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 since10, 11. 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 records17, 18.

1. Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
2. Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK
4. School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK
5. Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA

Correspondence to: Robert M. DeConto1 Correspondence and requests for materials should be addressed to R.M.D. (Email: [email protected]).

 

[ding]

[Do whatever the fuck you want little boy.

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]

[Do whatever the fuck you want little boy.

Maybe you need to be educated on how atmospheric CO2 is measured and what those reading show. I wonder if you can point out for me when the atmospheric CO2 levels reached 280 ppm? Because 280 ppm is what the author' stated was the threshold for northern hemisphere glaciation.

 

[ding]

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]

Missed a significant point there Mr Ding. The Earth does not currently possess "major continental-scale Northern Hemisphere glaciation".

 

[ding]

Missed a significant point there Mr Ding. The Earth does not currently possess "major continental-scale Northern Hemisphere glaciation".

Wow... you are consistent. You have been proven wrong without a shadow of a doubt and you still can't admit it?