PRAG meeting Monday 21st November 8 pm UK time
John Nissen
2022-11-18
A MODEL OF EARTH SYSTEM OPERATION AS A BASIS FOR PLANETARY RESTORATION
Abstract
We introduce a theoretic model of Earth System behaviour based on Milankovitch cycles and observations of temperature and sea level from the late Eemian up to the early Holocene. The late Holocene had exceptionally stable climate, temperatures and sea level compared to this previous period. The Earth System left this period of anomalous stability with an acceleration of Arctic warming from around 1980, as shown by surface and satellite measurements. The Arctic appears to be switching from a state with sea ice throughout the year to a state where there is very little sea ice by the end of summer and we show how weather extremes are becoming ever more severe as a result. Our model of Earth System behaviour can be used as a basis for restoration of the Earth System to its 1980 state or earlier, starting by cooling the Arctic using SRM (solar geoengineering) since SRM techniques provide the most powerful cooling capability currently available. Research is urgently needed into optimum safe deployment of SRM, in the light of this model which predicts high risk of catastrophic climate change and sea level rise if powerful cooling action is not taken quickly.
Introduction
The current policy of CO2 emissions reduction, accepted by the majority of nations, is inadequate to address accelerating climate change and sea level rise. Sudden vast changes in climate and sea level have occurred in the past and could be happening again, triggered by global warming. Our objective is to show that an understanding of Earth System operation can point to practical and affordable SRM cooling techniques for quickly reversing climate change, slowing sea level rise and restoring the planet to a demonstrably safe and sustainable state in which future generations can prosper. Cooling the Arctic is particularly urgent.
We are aware of a number of barriers to be overcome: firstly a huge and scientifically unwarranted stigma attached these cooling techniques; secondly the resistance of the climate science community (and the governments who fund their research) to any change in policy; and thirdly the opposition of certain countries and industries to the refreezing of the Arctic. But perhaps the largest barrier is that of disbelief: people cannot reconcile the idea that intervention is required with their innate belief in the stability of the Earth System, as embodied in Mother Nature.
Milankovitch warming signals
The most important Milankovitch cycles are produced by variations in the distance of the Earth from the sun (100 kyr cycles of eccentricity), the angle of the Earth’s axis to its orbital plane (41 kyr cycles of obliquity), and the direction that this axis is pointing (26 kyr cycles of precession). These three independent cycles together produce variations of the total amount of insolation in the Northern Hemisphere summer. Periods of deglaciation coincide with peaks of this insolation. For the past million years they have been about 100k years apart until the Eemian which ended about 120 kya. The thermal maximum within the Holocene was around 8 kya and followed a peak Milankovitch warming signal in the Northern Hemisphere (NH) summer.
Milankovitch signals and climate change
The Earth System (ES) is asymmetric with land around the South Pole and sea around the North Pole. This has been the case for the last 2.58 million years to the present day: a period known as the Quaternary. Snow more naturally settles on land, accumulating to form an ice sheet. There is naturally more ice in Antarctica than in the Arctic, and it is colder. This asymmetry has remained for the whole of the Quaternary. But within this time there have been alternating glacial and interglacial periods synchronised by Milankovitch signals. Entering a glacial period, the ice in the north greatly expands and sea levels fall. Entering an interglacial, the ice in the north contracts and sea levels rise. Between the glacial and interglacial maxima, temperatures vary by around 10C and sea levels by around 125 metres.
There is a sophisticated mechanism – a subsystem of the ES – which amplifies the Milankovitch signal (peak warming in NH summer) and warms the whole planet, melting ice everywhere and raising the sea level. Sometimes this is sufficient to take the planet firmly into an interglacial period. If so, the planet may move back into a glacial period when the warming signal subsides.
In our model of ES operation, the essential components of this mechanism include the Gulf Stream, the AMOC, the GIS and the Hadley cell structure of atmospheric circulation. Evidence comes from pollen, ice cores, ice-rafted debris (IRD) and reverse modelling. IRD appears in the North Atlantic after NH temperatures have peaked, as recorded in pollen and Greenland ice cores. This shows that giant icebergs have been discharged from Arctic glaciers and have floated thousands of kilometres before completely melting. Reverse modelling, in which a climate model for the Arctic is run backwards to reconstruct the past, suggests that the Arctic Ocean became seasonally ice free during the Early Holocene, see below.
Amplifying and switch mechanism
The amplification of the Milankovitch signal is certainly obtained primarily through melting of Arctic sea ice. This reduces albedo in the Arctic causing positive feedback: a vicious cycle of warming and melting. The warming also causes snow retreat and further positive albedo feedback. (At present the forcing has reached about 1.0 W/m2, globally averaged, according to Peter Wadhams.)
The heat of the Milankovitch signal is absorbed by surface water flowing into the Arctic. The majority of surface water north of 50N flows into the Arctic: from the Atlantic, from the Pacific, and from large Canadian and Siberian rivers. A prime source is the Gulf Stream, which gets extra summer heat from insolation across the sub-tropics. The Gulf Stream sends a jet of warmed water across the North Atlantic towards the British Isles and Norway. This water acts like the jet in a liquid switch, switching the Arctic Ocean towards a seasonally ice-free state. Conversely any diversion, dilution or cooling of the jet has an amplified effect in the Arctic to restore perennial sea ice.
There is strong evidence that, leading up to the Holocene thermal maximum, the Arctic Ocean became seasonally free of sea ice for a thousand years or more. This would have been the result of rapid warming as the Milankovitch approached its maximum. A decline in the signal, plus a large injection of cold freshwater into the North Atlantic or the Arctic Ocean itself, would have switched the Arctic Ocean back to the perennial state.
The past role of CO2
CO2 takes a subsidiary role in the coming and going of glacial periods (“ice ages”). Milankovitch cycles are the prime drivers for the major changes in the past, not CO2. Thus trying to correlate past temperatures with CO2 in order to determine the “climate sensitivity” of the planet is misguided. Certainly the CO2 level has reacts to temperature: its concentration decreases as oceans cool and vice versa. But this is a reactive effect rather than a driving effect. It can be clearly seen in the Early Holocene records.
At the depth of glacial periods, oceans are cool and the CO2 level declines. On theory is that, at around 185 ppm, the decline is sufficient to produce die-off in forests and grasslands, releasing CO2 and methane into the atmosphere as a negative feedback to the cooling. The low temperature certainly results in arid conditions and more dust being blown onto the oceans, which increases productivity but possibly has a positive feedback to the cooling [?].
At the glacial maximum, 21 kya, the concentration of CO2 was about 185 ppm. A rise in concentration from 185 ppm to around 270 ppm took place prior to the start of the Holocene 11.7 kya. There was then a decline to 264 ppm by 9 kya. Then CO2 increased to 280 ppm by around 1900, the baseline used by IPCC. This increase in CO2 is claimed to have largely offset cooling produced a reduction in the Milankovitch signal according to the Ruddiman hypothesis, see below.
Since 1900, concentrations of CO2 have increased steadily and the forcing effect from this excess CO2 in the atmosphere is around 2.0 W/m2. CO2 concentration is now the major driver of global warming.
Ruddiman hypothesis
A cooling period started around 6 kya, but much of this cooling has been offset by human emissions of greenhouse gases according to the Ruddiman hypothesis: both CO2 from the burning of wood and methane from the production of rice is paddy fields. During cold spells there was more burning of wood, which provided a Gaia-like negative feedback to the cooling. Rising heat produced pandemics, less burning of wood and less rice production, thus reducing the levels of CO2 and methane.
Arctic amplification effects on sea level rise and weather extremes TBD
Basis for planetary restoration TBD
robbi...@gmail.com
Link for our Planetary Restoration Action Group Meeting
https://us02web.zoom.us/j/89101098507?pwd=TlhaVFgvR2RKbk1HRU1wd254cXBSZz09
8pm UK = 7am Tuesday AEDT = noon Monday California
Robert Tulip
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rob...@rtulip.net
Link for our Planetary Restoration Action Group Meeting
https://us02web.zoom.us/j/89101098507?pwd=TlhaVFgvR2RKbk1HRU1wd254cXBSZz09
8pm UK = 7am Tuesday AEDT = noon Monday California
Robert Tulip
From: planetary-...@googlegroups.com <planetary-...@googlegroups.com> On Behalf Of John Nissen
Sent: Monday, 21 November 2022 11:24 AM
To: Planetary Restoration <planetary-...@googlegroups.com>
Cc: healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>; 'Eelco Rohling' via NOAC Meetings <noac-m...@googlegroups.com>; Kyle K <kylerk...@gmail.com>; Rafe Pomerance <rafe.po...@gmail.com>; Gernot Wagner <Ger...@gwagner.com>; Shaun Fitzgerald <sd...@cam.ac.uk>
Subject: [prag] PRAG meeting Monday 21st November 8 pm UK time
Hi all,
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peterlin...@gmail.com
This article in The New Yorker by Bill McKibben may be of interest.
To view this discussion on the web visit https://groups.google.com/d/msgid/planetary-restoration/046701d8fd9f%24e12008b0%24a3601a10%24%40rtulip.net.
John Nissen
Read this letter! At last, somebody is challenging the IPCC strategy and proposing both CDR and SRM to boot. And in the Guardian! Hooray and Cheers, John
Richard Mountford (Guardian letters, 22nd November)
Cop27 has shown why a new economic order is vital
For three decades, world leaders at international conferences have pledged to cut greenhouse gas emissions and greener energy sources have been developed, yet emissions have continued to rise (World still ‘on brink of climate catastrophe’ after Cop27 deal, 20 November). Even as previously extreme weather events become normal and millions of people are displaced by weather-related events, there is still no sign of electorates in richer countries being willing to vote for rationing or much higher prices for car use, air travel, meat consumption and other particularly damaging activities.
Clearly,
we urgently need a new strategy. The world’s biggest economies or the UN need
to spend hundreds of billions of dollars, perhaps funded by a financial
transactions tax, on carbon scrubbing and ocean seeding to remove carbon
dioxide from the atmosphere; solar radiation management to reduce warming; and
the purchase and protection of land such as rainforest to prevent its
destruction.
Richard Mountford
Hildenborough, Kent
rob...@rtulip.net
Here is a response I have written to Bill McKibben’s 22 November New Yorker article, published at the Planetary Restoration Action Group blog.
https://planetaryrestoration.net/f/response-to-bill-mckibben---how-to-cool-the-planet
Robert Tulip
Douglas Grandt
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Douglas Grandt
On Nov 24, 2022, at 2:54 AM, 'Douglas Grandt' via Healthy Planet Action Coalition (HPAC) <healthy-planet-...@googlegroups.com> wrote:
Michael Mann has retweeted Bill McKibben’s announcement
My reply to Mann
Clive Elsworth
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