“Come, Ahab’s compliments to ye; come and see if ye can swerve me. Swerve me? ye cannot swerve me, else ye swerve yourselves! man has ye there. Swerve me? The path to my fixed purpose is laid with iron rails, whereon my soul is grooved to run. Over unsounded gorges, through the rifled hearts of mountains, under torrents’ beds, unerringly I rush! Naught’s an obstacle, naught’s an angle to the iron way!”
— Herman Melville (1819-1891), Moby-Dick, Chapter 37.
This is one of many passages, in Herman Melville’s 1851 novel, Moby-Dick, describing Captain Ahab’s monomaniacal obsession to hunt down and kill the white bull sperm whale whose name is the novel’s title. (1) Ahab sought vengeance for being scarred — with curved conical teeth up to 20 cm (8 in) long and weighing up to 1 kg (2.2 lb) each — from head to knee and having his leg torn off, against Moby Dick, who had fought off a pursuit by whalers led by Ahab on a previous voyage:
“Aye, Starbuck; aye, my hearties all round; it was Moby Dick that dismasted me; Moby Dick that brought me to this dead stump I stand on now… Aye, aye! it was that accursed white whale that razed me; made a poor pegging lubber of me for ever and a day!… and I’ll chase him round Good Hope, and round the Horn, and round the Norway Maelstrom, and round perdition’s flames before I give him up. And this is what ye have shipped for, men! to chase that white whale on both sides of land, and over all sides of earth, till he spouts black blood and rolls fin out.”
But Starbuck, the First Mate aboard their ship, the Pequod, was having none of it. Starbuck was a devout Christian, a Quaker, eschewing all violence except for the hot bloody rush of catching and killing whales to boil their blubber down to the fine oil that would fetch handsome profits at the Nantucket market. Starbuck objects to his commander’s private scheme hijacking the Pequod and her crew from “the business we follow… I came here to hunt whales, not my commander’s vengeance.” To Starbuck, Ahab’s obsession is not only a derailment of their business but even an affront to God, because Ahab is intent to avenge himself on Nature itself through its organic manifestation as this one mighty white whale:
“Vengeance on a dumb brute!” Starbuck replies to Ahab, “that simply smote thee from blind instinct! Madness! To be enraged with a dumb thing, Captain Ahab, seems blasphemous.”
As regards human activity, Starbuck was right, but we now know that sperm whales are intelligent animals, like all cetaceans, and not purely dumb brutes: they have both memory and intent. The sperm whale brain is the largest known of any modern or extinct animal, weighing on average about 7.8 kilograms (17 lb), more than five times heavier than a human’s, and has a volume of about 8,000 cm^3. The sperm whale’s cerebrum is the largest in all mammalia, both in absolute and relative terms. (2)
The story, Moby-Dick, is famous around the world and most people know that Ahab and all his crew except one, Ishmael, perished in a failed attempt to wreak Ahab’s vengeance, which even cost the sinking of the Pequod, stove in by Moby Dick’s ramming. The novel is much much more than merely its sea adventure plot, and description of 19th century whaling. It is a roving philosophical inquiry into the nature of character, faith and perception; as well as a metaphor for Melville’s ruminations on American democracy, which was shifting from a free association of agrarian ruralists to an increasingly industrialized regimentation of expansionist outlook. Melville’s Moby-Dick, along with Mark Twain’s Huckleberry Finn (1885), are the quintessential American novels (in my opinion, at least).
A key point in Moby-Dick is that the crew willingly joined into Ahab’s scheme, and despite Starbuck’s opposition to it. By rights, and whaling industry regulations and customs, the officers and crew of the Pequod were duty-bound to wrest control of the ship from Ahab because he was usurping the use of the vessel and its personnel for his private ends, and away from its intended purpose. The fully outfitted Pequod, bound on a three year hunting expedition, represented the investments of the owners and many shareholders, including widows and orphans of lost Nantucket whalers, as well the ongoing labor investments of the Pequod’s crew, which were to be paid out of the expected harvest of whale oil.
Maximizing that harvest was the whalers’ business, and it was intended to be pursued as a voluntary association of men into a hierarchical organization glued together by a commonality of personal financial interests. Ahab used his fearsome magnetic personality, like witchcraft, to steal the souls of his men and make them instruments for the implementation of his own personal hatred. Carl Gustav Jung (1875-1961), the great Swiss psychiatrist and psychoanalyst, made this exact diagnosis of Adolph Hitler (1889-1945) and the German nation under his dictatorship during 1933 to 1945. (3) That same diagnosis can be applied, in varying degrees, then and now, here and abroad, to many political “leaders.” The eternal question for the many laboring crews of the many workshops of this world — agrarian and industrial — is: do we work dutifully to the death, or till cast adrift as expendable, and do we willingly follow the leader to perdition if he is hellbound and determined for it; or do we rebel, overturn the structure of command, and lead ourselves even if such freedom entails a hard life?
And this brings me to global warming climate change: fossil fuels are the opiates in the addiction to war that would be the death of humanity by Planet Earth’s rejection of it.
Do we work dutifully to the death, or till cast adrift as expendable, and do we willingly follow the leader to perdition if he is hellbound and determined for it; or do we rebel, overturn the structure of command, and lead ourselves even if such freedom entails a hard life? Is humanity as a whole worth our individual pains in this effort? Or, is the idea of restructuring human civilization — and soon — to jettison capitalism, authoritarianism, and their enabling fossil-fueled militarism and marbling corruption, just a chimera that would use up our individual life forces to no avail; is it simply better to accept the inevitability of inequitable finalities and “Gather ye rosebuds while ye may,” as Robert Herrick (1591-1674) wrote? (4)
I, personally, rebel at this surrender because I see it as a betrayal of our young people, and an insult to our honor and to our fully liberated frontal lobe intelligence (though much of that is neglected and unused, I’ll grant) and our technical capabilities. But I don’t dismiss the question: I guess I’ve gotten old.
It has been 31 years since climatologist James E. Hansen, in testimony to the U.S. Congress in June 1988, made one of the first assessments that human-caused warming had already measurably affected global climate. Shortly after, a “World Conference on the Changing Atmosphere: Implications for Global Security” gathered hundreds of scientists and others in Toronto. They concluded that the changes in the atmosphere due to human pollution “represent a major threat to international security and are already having harmful consequences over many parts of the globe,” and declared that by 2005 the world should push its emissions some 20% below the 1988 level. (5)
Since then, basically, nothing substantive has been done by our governments to combat this existential threat. And today the reality of global warming climate change — the crisis of continuing existence — is known, viscerally, to everybody (even the liars).
Our geophysical problem is the slowing of the advance of global warming, by drastically reducing the rates of continuing accumulation in the atmosphere of carbon dioxide, methane, and other greenhouse gases (like volatile organic compounds, VOCs) whose aggregate heat-trapping mass could push Earth’s climate system past an unknown threshold or “tipping point,” triggering a sudden and catastrophic transition to climatic conditions significantly more hostile to human survival.
What may not be fully appreciated is that our geophysical problem may be far beyond human capabilities to ever be resolved even were humanity to metamorphose itself through a rapid social evolution producing a miraculous reformulation of human civilization into an enlightened temporal Nirvana liberally powered entirely by green energy.
Will climate change drive humanity to extinction? If so, how much time have we got?, and how will it happen? These questions are on the minds of many people today. In this essay, I will follow paleontologists deep into the geological past to see if it can offer any analogs to the evolving climatic conditions of today, and in that way give us a window into our future.
Average Global Surface Temperature History
The trend of average global surface temperature between 1900 and 2100 — relative to the average temperature during 1951 to 1980 (the “datum” for our temperature scales here) — is shown in the following figure (6).
Projections (colored lines), with uncertainty bounds of ±1 standard deviation (shading), for future surface temperature rise from models that use different economic scenarios. Scenario A2 (in red) represents “business as usual” where temperature is projected to rise by the end of the century between 2°C and 5.5°C if no effort is made to constrain the rise of CO2 concentration in the atmosphere, which by 2100 could range between 525ppm and 1000ppm (ppm = parts per million of the air volume). The solid bars at right indicate the best estimate (solid line) and possible ranges (grey shading) for each scenario. (6)
A view of this relative temperature history between 1880 and 2016 follows.
Notice that the temperature distance from the 1951-1980 average global surface temperature ranges from -0.8°C (1917) to +1.3°C (February 2016). Planet Earth today is about 1.5°C warmer than it was in the 19th century. What was the global surface temperature at earlier times?
Planet Earth has gone through many cycles of glacial and interglacial intervals over the previous 800,000 years. During those Ice Age climatic oscillations, the concentration of carbon dioxide gas (CO2) in the atmosphere cycled between about 170ppm and 300ppm, and temperature cycled between about +4°C and -10°C about our mean global surface temperature datum. (7)
Climate change during the previous 65 million years has been charted as follows. For the details of this image, see note (8).
The green trace shows oxygen isotope measurements (for the oxygen-18 isotope as a fraction of the oxygen present in the sample) on the stacked layers of carbonate (chalk) deposits down through the seafloor (obtained by core drilling), formed from the compacted shells of ancient foraminifera. Temperatures later than 13Mya (Mya = million years ago) are shown in the box at the lower right of the above image; the dashed horizontal line indicates the datum. Temperatures (relative to the datum) between 65Mya and 35Mya are shown in the box in the upper left of the image. Antarctica was glaciating, thawing and reglaciating between 35Mya and 13 Mya, and science has insufficient data to determine the temperature history for that complicated interval. (8)
Notice the little spike labeled PETM, at 56Mya in the image above. This is the Paleocene-Eocene Thermal Maximum, a very short-lived (200,000 years) high temperature excursion. The height of this temperature spike is likely underestimated by a factor of 2 to 4 because of the coarse sampling and averaging involved in this record.
At least since 1997, the Paleocene–Eocene Thermal Maximum has become a focal point of considerable geoscience research because it probably provides the best past analog by which to understand impacts of global climate warming and of massive carbon input to the ocean and atmosphere, including ocean acidification. Although it is now widely accepted that the PETM represents a “case study” for global warming and massive carbon input to Earth’s surface, the cause, details and overall significance of the event remain perplexing. (9)
Paleocene–Eocene Thermal Maximum (PETM)
The paleogeography of 56Mya was not that different from today; there was no ice at the poles, the Atlantic Ocean was not as wide as it is now, and India was only just beginning to collide with the rest of Asia. The climate during the Eocene Epoch (56Mya to 34Mya) was much warmer then today: Redwood trees grew in the Canadian Arctic, and the environment of that polar region looked like Okefenokee Swamp (straddling the state boundaries of present-day Florida and Georgia); mid-latitude continental interiors were warm through the winter, with giant palms growing in Wyoming and crocodiles ranging through the swamps and rivers. The poles remained ice-free during the entire interval spanning the Paleocene Epoch (66Mya to 56Mya) and the Eocene Epoch (56Mya to 34Mya).
The expected rise in average global surface temperature during the 90 years between 2010 and 2100 is like the rise in global temperature, going backwards in time, from ‘now’ to 35Mya: about 4°C to 5°C above the datum. “In just a few human lifetimes we’re going to change conditions in the atmosphere to a state that hasn’t been seen in 35 million years” commented Dr. Scott Wing (Curator of Fossil Plants, Smithsonian Museum of Natural History, Washington, DC) in his detailed lecture on the PETM. (10)
During the Paleocene, CO2 concentration in the atmosphere (also called “partial pressure”) was estimated to have been at 380ppm to 400ppm, and then rose to 800ppm just prior to the onset of the PETM (56Mya), producing a global temperature about 4°C warmer than our datum. The CO2 concentration then doubled or more to at least 1600ppm to 2000ppm within a few millennia at the start of the PETM, ‘quickly’ (in geological terms) producing an additional temperature rise of 4°C to 8°C.
Between 4,000 and 7,000 billion tons of carbon were injected into the atmosphere within the initial millennia of the PETM; the first (and biggest?) pulse lasting less than 2,000 years, and the emissions ending within 20,000 years. It would take the natural processes of CO2 removal 200,000 years to return the CO2 concentration and the global temperature to their levels prior to the onset of the PETM.
The amount of carbon injected into the atmosphere during the PETM is about the size of the carbon burp that would (will?) be realized by burning the entire fossil fuel reservoir humanity has at its disposal. However, the rate at which atmospheric carbon (CO2 and CH4) was emitted during the PETM is at least 10 times slower than today’s anthropogenic emissions! What may have taken 3,000 years during the PETM, we are accomplishing within 300 years; in fact 200 million years of fossil fuel accumulation has been burned in about 160 years.
The essential point here is that it will take 100,000 to 200,000 years to get back to the “normal” climate we left behind us in the middle of the 20th century. On this, Dr. Scott Wing commented: “The effects last for 200,000 years. So this is a global shift, which to a geologist looks like a transient change, like a perturbation, like a blip, but to any sane human it’s forever.”
Where did PETM carbon emissions come from? Science does not have a definitive answer, but its four estimates, ranked from most likely to least likely are:
— methane bubbling up out of warmed deep ocean methane hydrates (ice-like solids trapping methane, produced by microbes feeding on decaying organic matter, and formed in the cold and high pressure at the bottom of oceans) and then oxidizing in the atmosphere (CH4 combining with oxygen to produce CO2 and water vapor);
— extensive wildfires that included the burning of peat deposits (because the burning of all terrestrial vegetation alone would have produced insufficient carbon, so the burning of peat would also have been necessary);
— volcanic intrusions into organic-rich sediments at the floor of North Atlantic off Scandinavia (a region of very active volcanism at the time) cooking the sediments to release CO2 and methane;
— the warming and oxidation of any permafrost that may have remained, and it giving up lots of carbon.
It is possible that a combination of these four effects may have occurred.
All the soils formed in the Big Horn Basin of Wyoming during the 200,000 years of the PETM have been compacted to stacked layers of sediments 40 meters thick in total. During the PETM that region had a warm dry tropical climate; bean plants proliferated. Before and after the PETM the climate was temperate and bean plants were absent from the Big Horn Basin (at least in the respective fossil records). During the first 150,000 years of the PETM, warm climate plants (like beans) moved north even to the Arctic, and then retreated south during the last 50,000 years of the PETM, with temperate climate plants reappearing.
Plants growing in a high CO2 environment make less green pigment and have lower nutritive value, so plant eaters have to eat more to sustain themselves, or evolve to smaller sizes to reduce their metabolic requirements. Animals and insects did both during the PETM. Ancient horses first appeared in America at the very beginning of the PETM, and they ‘quickly’ shrank in size by about 30% — to the size of domesticated cats today. With the uptake of CO2 at the close of the PETM and the return to ‘normal’ Eocene conditions, this species of tiny horses increased in size by 76%. A similar shrinkage of body size during the PETM occurred for the other mammal species present at the time, including primates.
The four major scientific lessons of the PETM are:
— big emissions of carbon into atmosphere result in warmer climate and more acidic oceans, and that acid seawater dissolves deep marine chalk (and kills marine organisms living in the lower few kilometers of the oceans because dissolved oxygen has been scavenged — hypoxia — and because shell formation, for the protective casings required by many marine organisms, is impossible because of the acidity);
— there are self-reinforcing cycles of carbon release with increased temperature: CO2 and CH4 capture and retain heat and warm the atmosphere; that warms the oceans and results in intermittent rainfall on the continents (heavy rains with long dry spells between); that causes an abundant growth of vegetation, which parches during the droughts and dry spells and feeds wildfires releasing more CO2, heating the atmosphere and oceans further; that leads to the dissociation of marine methane hydrates, which release methane gas and heat the atmosphere and oceans even further; a sequence of vicious cycles;
— rapid global warming changed where plants and animals lived and how they interacted (this is affecting 21st century people, too), and drove rapid evolution in the body sizes (shrinkage) of mammals;
— and the effects last for 200,000 years because it takes Nature that long to clear out the excess CO2 from the atmosphere and oceans.
What brought the CO2 concentrations down and ended the PETM? The process of photosynthesis in growing plants pulled CO2 out of the air and bound it into nutrients (sugars, glucose, plant tissues), which partially migrated into animal tissues as food. CO2 was also absorbed by the surfaces of the oceans, and reacted at depth with carbonate compounds to dissolve the sea floor chalk and acidify the seawater. Over a longer term, 10% to 30% of the excess CO2 was removed by weathering reactions in soils, and the erosion by rain and streams of rocks imprisoning CO2 carried sediments back to the oceans, where they settled out on the sea bottom. Long after the time scale of the PETM, those seafloor sediments would be interred by subduction at tectonic plate boundaries.
Carbon uptake is slow. A computer simulation of the instantaneous dumping of 5,000 billion tons of carbon into atmosphere (producing an atmospheric concentration of 2,500ppm of CO2, by volume) showed that:
— roughly half of the CO2 comes out in first 1,000 years;
— 30% to 40% still remains at 10,000 years;
— and it isn’t all removed until after 100,000 years, so by about 150,000 to 200,000 years as occurred with the PETM.
A visual representation of CO2 uptake follows (11)
For a detailed description of the CO2 uptake processes, see note (11).
Similar computer modeling has been done for our climate future out to year 3000. Assuming that the entire fossil fuel reservoir is burned up by year 2100, injecting 5,000 billion tons of carbon into the atmosphere, the global temperature will rise to 4.5°C above datum by 2100 and remain there. Among the expected effects are a sea level rise of 1 meter by 2100, and 7.5 meters (25 feet) by year 3000 because the Greenland Ice Cap will have melted.
The major problem of having elevated global temperature for a long time — and it will be long since Nature takes “forever” to reabsorb atmospheric CO2 — is that major melting will eventually occur. As we are learning from direct observation today, that major melting may occur more rapidly than scientists were at first led to believe on the basis of their earlier computer modeling. If the Antarctic Ice Cap were also to entirely melt, sea level would be 66 meters (216 feet) higher in an ice-free world.
Could humanity today go on a furiously massive campaign to plant more trees and vegetation, so as to suck out excess CO2 from the atmosphere and stop global warming? No. We just can’t emplace enough plants to accomplish this, the rate of CO2 removal implied by this question is beyond the capability of Earth’s biosphere however lush. However, increasing the mass and area of vegetation (plants, trees) would slow the rates of CO2 accumulation and temperature increase, and help us lose ground (against the advance of global warming) less rapidly. So yes, plant!; it would also be a relief to wildlife sorely pressed with habitat losses.
Life in the Anthropocene
Geologists have recognized that we are now living in an epoch whose climate is fundamentally affected by human activity. That epoch has been termed the Anthropocene (12), and it was officially designated to have begun in the 4th quarter of 1965. (13)
“We have started the Anthropocene but the things that we think are untrammeled nature are already trammeled by us. There’s no eco-system on this planet that hasn’t had the human fingerprint on it some way or another. And many of the things that we think are beautiful and natural have already been modified by our ancestors, in ways that may not be obvious to us… What the Anthropocene perspective does is it helps us recognize that with [over] 7 billion people on the planet, and thousands of years, tens of thousands of years-long history already of modifying the planet, that it’s really too late to think about putting anything back the way it was,” Dr. Scott Wing.
I can think of 9 possible negative effects (mainly on human civilization) from severe global warming:
— reduced food production on land because of droughts and desertification, and a reduction of the nutritive value of crops because of high CO2 concentration;
— increased scarcity of fresh water, because of hot dry climatic conditions, intermittent rainfall, and huge population;
— the global spread of disease germs and usually tropical parasites, in a hotter world;
— loss of seafood with acidic seas, and increased starvation for animals and people;
— habitat losses for people, given significant coastal inundation and excessive heat and desertification in continental interiors;
— habitat losses for terrestrial wildlife as with humans, but also for marine life because of the reduced dissolved oxygen and increased acidity of the oceans;
— climate disaster-sparked mass migrations, which among humans will undoubtedly lead to clashes and even wars;
— resource scarcity wars (for basics like water, and for rarities like the semiconductor materials and metals essential to high tech electronics, and maybe in the extreme even for uranium deposits);
— increasingly heartless exclusion of the poor by the rich and powerful (a worldwide ‘Gazafication’ of the hapless poor).
We see some of each of these today, but the questions are: how much worse could it get?, and by when?
The development of human civilization over the last 10,000 years or so was aided by the benevolence of a very stable and moderate interglacial climate. In this new Anthropocene Epoch of increasing climate instability, we can anticipate major disruptions in human affairs, and given the socio-economic disparities and hostilities built into our human societies, we can anticipate the burdens of those disruptions to fall inequitably on poorer people. Misery will pushed down the gradient of wealth towards the destitute. In an extreme projection of pessimism, one could imagine conflicts of immiseration avoidance to devolve into extinction events, like a nuclear war.
However, the anticipated climate variations, like those of the PETM, will not in themselves be sufficiently extreme to force the actual physical extinction of humanity. In 7.95 billion years, when the Sun expands into a Red Giant star, then life on Planet Earth will be evaporated. But until such time, the most likely cause of a premature human extinction would be bad human behavior in response to the climate changes confronting humanity, and which we have caused.
It would be good for us to become familiar with how life is distributed in the Anthropocene, the epoch whose gallop we are spurring, so we can lead it more thoughtfully.
Humanity today comprises only 0.01% of all life on Planet Earth, but over the course of human history our species has destroyed 83% of wild mammal species. (14)
“The world’s 7.6 billion people [in May 2018] represent just 0.01% of all living things, according to the study. Yet since the dawn of civilisation, humanity has caused the loss of 83% of all wild mammals and half of plants, while livestock kept by humans abounds. The new work is the first comprehensive estimate of the weight of every class of living creature and overturns some long-held assumptions. Bacteria are indeed a major life form – 13% of everything – but plants overshadow everything, representing 82% of all living matter. All other creatures, from insects to fungi, to fish and animals, make up just 5% of the world’s biomass. Farmed poultry today makes up 70% of all birds on the planet, with just 30% being wild. The picture is even more stark for mammals – 60% of all mammals on Earth are livestock, mostly cattle and pigs, 36% are human and just 4% are wild animals.” Where is all that life to be found?: 86% on land, 1% in the oceans, and 13% as deep subsurface bacteria. (14)
One suggested marker for the Anthropocene are the bones of domestic chickens, which are now ubiquitous around the globe. The marker recognized has having achieved complete coverage over the surface of Planet Earth by late 1965 is radioactive fallout from atmospheric atomic and nuclear bomb explosions.
Remember that the biggest threat to humanity’s survival is anti-social human behavior; climate change alone can’t kill us.
If we choose to experience our present and future of changing climate as a competitive war game — with actual killing and willful destruction — to gain class, factional and ideological advantages in terms of physical security, habitability, food production, natural resource availability, standard of living and social status (ego gratification), then that species-wide dysfunctional response could ultimately lead to a collapse of civilization, and at its worst to a global nuclear war and then actual human extinction.
If we choose to experience our present and future of changing climate as an intellectual challenge to human ingenuity for technical innovation, and as a moral challenge for social organization and for the elimination of socio-economic disparities, then such a species-wide response would improve the human condition regardless of the degree of future climate variability and the geographical distribution of its effects on habitability.
Regardless of what we do or don’t do, the climate will change in ways governed by majestic and interlocking geophysical cycles spanning millennia. Our individual and species-wide experiences of living within this implacable reality will be set by how we choose to interact with each other. Nirvana or perdition are choices entirely within our grasp.
Many will say that obviously climate change as competitive war game is the only realistic alternative because it requires no behavioral changes from our over 10,000 years of “civilized” human history, and because eco-socialism is pure utopianism and thus beyond all realistic actualization. And of course, eco-socialism is impossible in a world of Ahabs and fanatical Ahab followers. But all that is just an excuse to continue with bad behavior. There are no actual physical or biological constraints preventing people from choosing to associate in an eco-socialist manner. The current societal improbability for deeply cooperative behavior does not make future species-wide collective cooperation an impossibility. Responding to climate change could provide a framework on which to build such a species-wide socialist civilization.
So, how would I respond to the Ahabs out there who would tell me: “Everything you say is wrong! God is White! Trump is Christ! Capitalism is Salvation! Ye cannot swerve me!” From me: You can’t accept it because then you wouldn’t be the person you are. You can’t learn if you are unwilling to change. And that, ultimately, is what climate change will be for us: a challenge to learn.
And finally, Nature to Ahab: Ye cannot swerve me! Your world may return in 200,000 years.
(1) Herman Melville, Moby-Dick or, The Whale, (1851), Penguin Books, 1992.
(2) Sperm Whale,
(3) Carl Gustav Jung, C. G. Jung Speaking: Interviews and Encounters, Princeton University Press, 21 February 1987, edited by: William McGuire and R. F. C. Hull; “Diagnosing the Dictators” 1938, pages 115-135; “Jung Diagnoses the Dictators” 1939, pages 136-140; (dictators = Hitler, Stalin Mussolini).
(4) “To the Virgins, to Make Much of Time,” (Robert Herrick)
(5) History of climate change science
(6) Global Surface Temperature, 1900-2100
(relative to 1951-1980 average global surface temperature)
National Research Council 2011. Understanding Earth’s Deep Past: Lessons for Our Climate Future. Washington, DC: The National Academies Press.
Figure 1.1, page 35 of the PDF file, page numbered 20 in the text.
Figure 1.1 SOURCE: IPCC (2007, Figure SPM.5, p. 14).
(7) Global view answers ice age CO2 puzzle
April 4, 2012 — andyextance
The 800,000 year record of atmospheric CO2 from Antarctic ice cores, and a reconstruction of temperature based on hydrogen isotopes in the ice. The current  CO2 concentration of 392 parts per million (ppm) is shown by the blue star. Credit: Jeremy Shakun/Harvard University
(8) 65 Million Years of Climate Change
(wikipedia, 13 July 2019)
This figure shows climate change over the last 65 million years. The data are based on a compilation of oxygen isotope measurements (δ18O) on benthic foraminifera by Zachos et al. (2001) which reflect a combination of local temperature changes in their environment and changes in the isotopic composition of sea water associated with the growth and retreat of continental ice sheets.
Because it is related to both factors, it is not possible to uniquely tie these measurements to temperature without additional constraints. For the most recent data, an approximate relationship to temperature can be made by observing that the oxygen isotope measurements of Lisiecki and Raymo (2005) are tightly correlated to temperature changes at Vostok as established by Petit et al. (1999). Present day is indicated as 0. For the oldest part of the record, when temperatures were much warmer than today, it is possible to estimate temperature changes in the polar oceans (where these measurements were made) based on the observation that no significant ice sheets existed and hence all fluctuation in (δ18O) must result from local temperature changes (as reported by Zachos et al.).
The intermediate portion of the record is dominated by large fluctuations in the mass of the Antarctic ice sheet, which first nucleates approximately 34 million years ago, then partially dissipates around 25 million years ago, before re-expanding towards its present state 13 million years ago. These fluctuations make it impossible to constrain temperature changes without additional controls.
Significant growth of ice sheets did not begin in Greenland and North America until approximately 3 million years ago, following the formation of the Isthmus of Panama by continental drift. This ushered in an era of rapidly cycling glacials and interglacials.
Also appearing on this graph are the Eocene Climatic Optimum, an extended period of very warm temperatures, and the Paleocene-Eocene Thermal Maximum (labeled PETM). The PETM is very short lived high temperature excursion possibly associated with the destabilization of methane clathrates and the rapid buildup of greenhouse gases in the atmosphere. Due to the coarse sampling and averaging involved in this record, it is likely that the full magnitude of the PETM is underestimated by a factor of 2-4 times its apparent height.
(9) Paleocene–Eocene Thermal Maximum (PETM)
(10) Global Warming 56 Million Years Ago, and What it Means For Us
30 January 2014
Dr. Scott Wing, Curator of Fossil Plants,
Smithsonian Museum of Natural History
(11) CO2 “lifetime” in the atmosphere
National Research Council 2011. Understanding Earth’s Deep Past: Lessons for Our Climate Future. Washington, DC: The National Academies Press.
Figure 3.5, page 93 of the PDF file, page numbered 78 in the text.
CO2 Sweepers and Sinks in the Earth System
The carbon fluxes in and out of the surface and sedimentary reservoirs over geological timescales are finely balanced, providing a planetary thermostat that regulates Earth’s surface temperature. Initially, newly released CO2 (e.g., from the combustion of hydrocarbons) interacts and equilibrates with Earth’s surface reservoirs of carbon on human timescales (decades to centuries). However, natural “sinks” for anthropogenic CO2 exist only on much longer timescales, and it is therefore possible to perturb climate for tens to hundreds of thousands of years (Figure 3.5). Transient (annual to century-scale) uptake by the terrestrial biosphere (including soils) is easily saturated within decades of the CO2 increase, and therefore this component can switch from a sink to a source of atmospheric CO2 (Friedlingstein et al., 2006). Most (60 to 80 percent) CO2 is ultimately absorbed by the surface ocean, because of its efficiency as a sweeper of atmospheric CO2, and is neutralized by reactions with calcium carbonate in the deep sea at timescales of oceanic mixing (1,000 to 1,500 years). The ocean’s ability to sequester CO2 decreases as it is acidified and the oceanic carbon buffer is depleted. The remaining CO2 in the atmosphere is sufficient to impact climate for thousands of years longer while awaiting sweeping by the “ultimate” CO2 sink of the rock weathering cycle at timescales of tens to hundreds of thousands of years (Zeebe and Caldeira, 2008; Archer et al., 2009). Lessons from past hyperthermals suggest that the removal of greenhouse gases by weathering may be intensified in a warmer world but will still take more than 100,000 years to return to background values for an event the size of the Paleocene-Eocene Thermal Maximum (PETM).
In the context of the timescales of interaction with these carbon sinks, the mean lifetime of fossil fuel CO2 in the atmosphere is calculated to be 12,000 to 14,000 years (Archer et al., 1997, 2009), which is in marked contrast to the two to three orders of magnitude shorter lifetimes commonly cited by other studies (e.g., IPCC, 1995, 2001). In addition, the equilibration timescale for a pulse of CO2 emission to the atmosphere, such as the current release by fossil fuel burning, scales up with the magnitude of the CO2 release. “The result has been an erroneous conclusion, throughout much of the popular treatment of the issue of climate change, that global warming will be a century-timescale phenomenon” (Archer et al., 2009, p. 121).
(13) The Anthropocene’s Birthday
(14) Humans just 0.01% of all life but have destroyed 83% of wild mammals – study
data sources for charts below
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