In my last post I did not directly address Hansen's ice-climate positive feedback mechanism on ECS, due to a progressive collapse of the WAIS this century (& which could begin as soon as with about twenty years), so I provide the following recent posts from other threads, that indicate that paleo-evidence confirms that a collapse of marine ice sheets in Antarctica accelerates Arctic Amplification (due to Hansen's ice-climate feedback & the bipolar seesaw mechanism); which can in-turn amplify ENSO-like behavior that can telecommunicate more atmospheric energy from the Tropical Pacific poleward (& particularly towards West Antarctica thus sustaining a collapse of the WAIS begun in the Byrd Subglacial Basin). If so this would dramatically increase the effective value of ECS this century:
Extract from the Human Stupidity thread:'
'The first linked article is entitled: "3M-year-old sediment tells the story of today's climate", and it discusses research about Lake El'gygytgyn, in Siberia, that began in 2009. Even through the findings of this research has been available for years (see the last two linked references), ESMs have not been able to replicate that amount of Arctic Amplification documented by the Lake El'gygytgyn physical evidence. This implies that the climate sensitivity of current ESMs need to be increased to appropriate capture the climate change risks (including Hansen's ice-climate feedback mechanism due to 'freshwater hosing' that we are collectively exposing ourselves to.https://www.eenews.net/stories/1060053182
Extract: "One of the "most astounding things" in the sediment, she said, was evidence that ancient summer temperatures in the region had spiked by as much as 14 degrees Fahrenheit higher than today, not just once, but several times in the past.
There is no direct way to measure the atmosphere of this ancient time, but repeated estimates from leaf stomata, ocean fossil studies and other remnants now put its carbon dioxide content at around 400 parts per million — about where it is today, largely due to the sharp rise of CO2 and other greenhouse gases since the Industrial Revolution began, literally gaining steam in the 1850s.
According to Brigham-Grette, that means the Earth is much more sensitive to climate change now, and it is speeding up as the planet tries to reach equilibrium from the new injection of heat.
The findings of the science team at Lake El'gygytgyn were also very hard for experts who use computer-driven climate models to understand. They pride themselves on being able to predict the speed of climate change in the future and also in the past by use of a technique called "hindcasting."
In the case of the late Pliocene, though, the models missed the ice melting. Yet the data collected from drilling in the Arctic and more recently from the Antarctic suggest it happened not just once, but repeatedly at both poles.
James White, a paleoclimatologist and climate modeler at the University of Colorado, Boulder, said Brigham-Grette's study is "one of the more important paleoclimate studies of the last 10 years."
"The fact that we don't get the Pliocene is a concern," he explained, because over the years, the modelers and the data gatherers have helped each other perfect their understanding of climate change and how to improve the models.
"We're not in equilibrium now, not even close," he asserted, as the planet's oceans struggle to distribute the new influx of heat.
A new Japanese study, published in February written by scientists from a team exploring ice cores drilled in Antarctica, found that ocean warming currents carrying heat from the tropics have become more unstable in the North Atlantic because of colder fresh water dripping from the melting ice of glaciers in Greenland. The phenomenon is called "freshwater hosing," which also appears to have happened in the ancient past.
"There's this attitude of 'Well, we're Americans, and we're going to tough it out and help people rebuild along our coastlines,'" she said. "Well, that's sort of stupid, because we're putting people and infrastructure back in harm's way.""
Gregory A. De Wet, Isla S. Castañeda, Robert M. DeConto & Julie Brigham-Grette (February 2016), “A high-resolution mid-Pleistocene temperature record from Arctic Lake El'gygytgyn: A 50 kyr super interglacial from MIS 33 to MIS 31?”Earth and Planetary Science Letters 436:56-63 DOI: 10.1016/j.epsl.2015.12.021 http://blogs.umass.edu/biogeochem/files/2016/01/de-Wet-et-al.-2016.pdf
Coletti, A. J., DeConto, R. M., Brigham-Grette, J., and Melles, M.: A GCM comparison of Pleistocene super-interglacial periods in relation to Lake El'gygytgyn, NE Arctic Russia, Clim. Past, 11, 979-989, doi:10.5194/cp-11-979-2015, 2015.http://www.clim-past.net/11/979/2015/cp-11-979-2015.pdfhttp://www.clim-past.net/11/979/2015/cp-11-979-2015.html
Extract from Hansen et al paper3+ meters SLR by 2100 thread:
"The Last Glacial Termination, LGT, occurred from 18,000 to 11,650 kya, and the following reference, reconstructs the dynamic response of the Antarctic ice sheets to warming in this period in order to better evaluate Hansen's ice-climate feedback mechanisms. The abstract concludes: "Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise."
Fogwill, et. al. (2017), "Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the last Glacial Termination", Scientific Reports 7, Article number 39979, doi:10.1038/srep39979https://www.nature.com/articles/srep39979