Guest post by Paul MacRae

In June, a NASA climate study announced that the warm middle Miocene era, about 16 million years ago, had carbon dioxide levels of 400 to 600 parts per million. The coasts of Antarctica were ice-free in summer, with summer temperatures 11° Celsius warmer than today. The study concluded that today’s CO2 level of 393 ppm was the highest, therefore, in millions of years, and could go to Miocene levels by the end of the century[1]. It was implied, although not directly stated, that readers should react with horror.
A UCLA team, writing in Science, had already pushed the Miocene button in 2009, claiming: “The last time carbon dioxide levels were apparently as high as they are today [15 million years ago, again the mid-Miocene]—and were sustained at those levels—global temperatures were 5 to 10 degrees Fahrenheit [2.7-5.5°C] higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland.”[2] Back to the Miocene! Scary!
James Hansen, the alarmist head of NASA’s Goddard Institute for Space Studies (GISS), regularly refers to past eras as a warning of the climate catastrophes that could occur today. For example, in 2011 Hansen warned: “[An increase of] two degrees Celsius is guaranteed disaster…. It is equivalent to the early Pliocene epoch [between 5.5 and 2.5 million years ago] when the sea level was 25m (75 feet) higher.” [4] Back to the early Pliocene! Horror!
And, in testimony to the U.S. government: “The Earth was much warmer than today in the early Cenozoic [which began 65 million years ago]. In fact it was so warm that there were no ice sheets on the planet and sea level was about 75 meters (250 feet) higher.” [5] Heavens! The planet could revert to the age of dinosaurs! (Hansen didn’t mention that sea levels today are 120 metres—almost 400 feet—higher than they were a mere 15,000 years ago, without creating a catastrophe.)
If we don’t curb our carbon-emitting ways, the alarmists warn, we face “increasingly radical temperature changes, a worldwide upsurge in violent weather events, widespread drought, flooding, wildfires, famine, species extinction, rising sea levels, mass migration, and epidemic disease that will leave no country untouched.” [7] The only catastrophe not mentioned here is “acidification” (i.e., a slight decrease in alkalinity) of the oceans.
If a warmer, more CO2-rich world would be hell in the future, it logically must have been hell in the past, too, when global temperatures were much warmer and carbon dioxide levels much higher. How could anything live, for example, in those “acidified” oceans of the Miocene? At least, this is what alarmist climate scientists like Hansen want the public to believe.
An Eocene ‘paradise’
Curiously, while alarmists warn about the horrors of returning to the climate of millions of years ago, paleoclimatologists tell a different story. They more often see our earlier planet as a “paradise,” even “paradise lost.”
In fact, “paradise lost” is the subtitle of a 1994 book on our planet 33 million years ago by veteran paleo-climatologist Donald A. Prothero—The Eocene-Oligocene Transition: Paradise Lost. The Eocene (55-33 million years ago) began what is sometimes called the Golden Age of Mammals. This geological age was at least 10°C warmer than today, free of ice caps, and with CO2 levels, Prothero suggests, of up to 3,000 parts per million, which is almost eight times today’s level of about 400 ppm. Yet Prothero calls the Eocene a “lush, tropical world.”[8]
At the end of the still very warm Oligocene (33-23 mya), Prothero puts CO2 levels at 1,600 ppm, or four times today’s levels.[9] Prothero’s 1994 CO2 estimates may be a high, but no one—not even Hansen—denies that CO2 levels were several times higher than today’s in the Eocene and Oligocene and, indeed, right down to the Miocene (23-5 mya).
For Prothero, the boundary between the Eocene and Oligocene was “paradise lost” because it was then, about 33 million years ago, that the planet began its slide from a “lush, tropical world” into its current ice age conditions (see Figure 1), with glaciations every 85,000 years interspersed with brief, 15,000-year warm interglacials.
Figure 1: Falling temperatures over 65 million years. Source: Global Warming Art.
In fact, the planet is currently its coldest in almost 300 million years. Yet, for Hansen and others in the alarmist camp, our ice-age world is in danger of getting too hot—maybe even as hot as the Pliocene, or the Miocene, or the Oligocene, or even, heaven forbid, the Eocene.
Many other writers on paleoclimate also use the term “paradise” to describe climate in the distant past. For example, in a history of evolution for younger readers, science writer Sara Stein paints the Eocene of 50 million years ago as follows:
“The world that all the little brown furry things [mammals] inherited from the dinosaurs was paradise. [emphasis added] The climate was so mild that redwoods, unable now to live much further north than California’s pleasant coast, grew in Alaska, Greenland, Sweden, and Siberia. There was no ice in the Arctic. Palm trees grew as far north as 50 degrees latitude, roughly the boundary between the United States and Canada. Below that subtropical zone—that was similar to Florida’s landscape today—was a broad band of tropical rain forest.”[10]
Sounds grim, doesn’t it?
One of the most prominent climate alarmists, Tim Flannery, also uses the “p” word when he describes Eocene North America in his very readable The Eternal Frontier,on the geological and biological history of North America. Flannery writes:
When Earth is warm (in greenhouse mode)—as it was around 50 million years ago—North America is a verdant and productive land. [emphasis added] Almost all of its 24 million square kilometers, from Ellesmere Island in the north to Panama in the south, is covered in luxuriant vegetation.[11]
Flannery titled the section of the book that deals with the “verdant and productive” Eocene as: “In Which America Becomes a Tropical Paradise.” Yet this was a time, it should be remembered, when temperatures and CO2 levels were much higher than today’s. Unfortunately, trapped in his alarmism, Flannery doesn’t see the irony.
British paleontologist Richard Fortey describes the landscape of Australia 20-35 million years ago, during the Oligocene and Miocene, as being “as rich as Amazonia, green and moist, with trees and ferns in profusion.”[12] Today much of Australia, an area the size of the continental United States, is desert and bush and supports only 22 million people compared to 300 million in the U.S.
As recently as 125,000 years ago, the peak of the last interglacial, our planet was 3-5°C warmer than today at the poles according to the Intergovernmental Panel on Climate Change (IPCC) itself, with sea levels 4-6 metres (12-20 feet) higher than today’s interglacial so far.[13] Even Britain was semi-tropical, with hippopotami gamboling in the Thames, apparently untroubled by extreme weather events, extreme droughts, extreme flooding, etc.
A mere 7,000 years ago, during the Holocene Optimum period that was at least 1°C warmer than today, much of the Sahara Desert was green, as were many other regions that today are desert.[14] Why? Because warmer temperatures mean less polar ice, making more water available for precipitation, and therefore promoting a greener planet.
So, millions of years ago, during geological eras much warmer than ours, with much higher levels of carbon dioxide, the planet faced the same environmental hazards as today—volcanoes, earthquakes, tsunamis and the like. But it was not plagued by the extreme weather events, extreme droughts, extreme flooding, mass extinctions, or even the ocean “acidification” claimed by climate alarmists for the world of the future.
Sea level ‘disaster’?
On only one point have the alarmists got it right: during these warmer times of the geological past sea levels were higher, sometimes many metres higher—a point Hansen mentions again and again in his presentations.
For example, Hansen notes that while only two per cent of the Earth’s land surface is within 10 metres of sea level, this two per cent also has 10 per cent (more than 630 million) of the world’s population. Hansen says a five-metre (15 foot) rise would, without costly dikes or other measures, inundate many large cities, including New York, London, Shanghai and Tokyo. This sea level increase, he concludes, would be “disastrous.”[15] Hansen even seriously predicts five metres (15 feet) of sea-level rise by the end of the 21st century under a Business As Usual carbon scenario.[16]
However, most climate scientists—even alarmist scientists—know that Hansen’s predictions are hallucinations and accept that a sea level rise of this magnitude could only take place over centuries and millennia, just as sea levels today have taken 15,000 years to rise 120 metres (400 feet).
For example, in 2006 the Sierra Club released a map of Victoria, British Columbia, flooded by a sea-level rise of from six to 25 metres (see Figure 2). The Sierra Club predicted that if we did nothing about carbon emissions, flooding of this magnitude could occur “in the lifetime of our grandchildren,” that is, within the century.[17]
Figure 2: Victoria, B.C., under water ‘in the lifetime of our grandchildren,’ according to the Sierra club.
Even University of Victoria climatologist Andrew Weaver, an arch-alarmist, was moved to protest against this barrage of exaggeration and misinformation, writing to the Victoria Times Colonist letters page: “The science suggests serious societal consequences of global warming in the short term, while the changes in sea level that the Sierra Club tout happen over thousands of years. [emphasis added] This clumsy story just makes it easy for the deniers to claim there is no problem.”[18]
The ultra-alarmist site de Smog Blog also joined the chorus against the Sierra Club’s absurd apocalyptism with a blog entitled “Sierra Club drowns in own climate catastrope” (the de Smog headline writer apparently could not spell “catastrophe”).
In other words, in the real world (as opposed to Hansen’s world), sea-level rise of any magnitude will take centuries and even millennia. The current rate of sea-level increase is just over 2 mm a year, or about 20 cm per century. At this rate—and at the moment the rate shows no signs of increasing—sea levels would take 2,500 years to reach Hansen’s five metres. Based on several interglacials over the past 600,000 years, which at their peak had sea levels several metres higher than today’s levels according to the IPCC, the seas would rise five metres or more even if human beings didn’t emit carbon.
Coping with sea-level rise
Can humanity cope with rising sea levels, whatever those levels may be? If climate alarmists don’t cripple our carbon-based economy, even the IPCC predicts that both developed and developing countries will have all the prosperity they need to cope with rising sea levels, be it seawalls, landfill, or relocations to desert and polar areas that, thanks to warmer temperatures and greater precipitation, are now fit for settlement.
Figure 3 shows GDP per capita for four of the IPCC’s climate scenarios, from Business As Usual (A1) to anti-carbon, between 1990 and 2100. In all four scenarios, humanity becomes better off, but humanity is best off in the red-line, A1 scenario, which is basically Business As Usual.
Figure 3: Figure 3: GDP per capita 1990-2100. The red line represents the IPCC scenario with the least attempt to stop climate change, which makes humanity the richest. Source: Arnell et al., 2004. [19]
In the red BAU scenario, the world’s per capita income will rise from $5,000 a year in 1990 to $70,000 a year in 2100, based on 1990 dollars. In other words, if we do nothing at all to try to stop global warming, by 2100 even poor countries will have the resources they need to adapt to climate change, whether warmer or cooler.
And, again, a warmer, wetter planet would “green” many of the world’s desert regions, including the Sahara and Australia, just as warming did in ages past. Meanwhile, thousands of square miles of land currently under ice or Arctic scrub would be open to settlement.
A wetter, greener world
And this still doesn’t take into account the positive effect of higher levels of CO2 in fertilizing plants. Physicist and biologist Sherwood B. Idso, who has specialized in charting the relationship between CO2 and plants, notes:
A simple 330 to 660 ppm doubling of the air’s CO2 content will raise the productivity of all plants, in the mean, by about one-third. … As atmospheric CO2 concentrations more than double, plant water-use efficiencies more than double, with significant improvements occurring all the way out to CO2 concentrations of a thousand ppm or more.
Think of what such a biological transformation will mean to the world of the future. Grasslands will flourish where deserts now lie barren. Shrubs will grow where only grasses grew before. And forests will make a dramatic comeback to reclaim many areas presently sustaining only brush and scattered shrubs. [20]
Sound utopian? Even the IPCC acknowledges that doubled CO2 levels can produce increases of up to 33 per cent in plant growth, while also making plants more drought resistant.[21]
Millions of years ago our planet was much warmer and wetter than today, with much higher levels of CO2. Alarmists like Hansen say a return to those temperatures and CO2 levels would be catastrophic. Yet our planet in earlier geological ages is almost always described as a tropical paradise, not a blasted, carbon-choked hell. Sea levels were higher, but a prosperous humanity can cope with higher sea levels.
However, the huge Antarctic ice cap—the “deep freeze” in our planet’s basement—didn’t exist in the Eocene or Oligocene. So even if the catastrophic warming hypothesis is valid—that’s doubtful, but if—it’s unlikely our planet will go back to Eocene or Oligocene warmth.
But if, as alarmists warn, we return to the Pliocene, or even the Miocene, would that be paradise lost? Or paradise regained?
Paul MacRae is a former journalist who now teaches writing at the University of Victoria. He is the author of False Alarm: Global Warming—Facts Versus Fears (Spring Bay Press, 2010). His website is paulmacrae.com. The book is available at springbaypress.com.
Sources
[1] “Study finds ancient warming greened Antarctica.” NASA website, June 17, 2012.
[2] “Last Time Carbon Dioxide Levels Were This High: 15 Million Years Ago, Scientists Report,” Science Daily, Oct. 8, 2009.
[3] James Hansen, “G-8 Failure Reflects U.S. Failure on Climate Change.” Huffington Post, July 9, 2009.
[4] Hansen, Address to American Geophysical Union, December 2011.
[5] Hansen, “Statement of Witness James E. Hansen.” No date given.
[6] Hansen, Storms of My Grandchildren: The Truth About the Coming Climate Catastrophe and Our Last Chance to Save Humanity. New York: Bloomsbury, 2009, p. 265.
[7] Nuclear lobbyist John Ritch. Quoted in Tom Zoellner, “Nuclear power gets its swagger back.” Globe and Mail, March 14, 2009, p. F5.
[8] Donald R. Prothero, Eocene-Oligocene Transition: Paradise Lost. New York: Columbia Univ. Press, 1994, p. 35.
[9] Prothero, pp. 22, 238
[10] Sara Stein, The Evolution Book. New York: Workman Publishing, 1986, pp. 245-246.
[11] Tim Flannery, The Eternal Frontier: An Ecological History of North America and its Peoples. London: Vintage, 2002, p. 84.
[12] Richard Fortey, Life: A Natural History of the First Four Billion Years of Life on Earth. New York: Alfred A. Knopf, 1998, p. 270.
[13] IPCC 2007 Summary for Policymakers, p. 9.
[14] See Wikipedia “Holocene climatic optimum” and “Green Sahara” for details.
[15] Hansen, “Climate Catastrophe.” New Scientist, July 28, 2007.
[16] Hansen and Makiko Sato, “Paleoclimate Implications for Human-Made Climate Change,” 2011.
[17] “Rising ocean would flood much of Greater Victoria.” Victoria Times Colonist, Dec. 6, 2006.
[18] Andrew Weaver, “Scary story sets back understanding.” Letter, Times Colonist, Dec. 8, 2006.
[19] Nigel Arnell, et al., “Climate and socio-economic scenarios for global-scale climate change impacts assessments: Characterising the SRES storylines.” Global Environmental Change, 14 (2004), p. 9. See also Indur Goklany, The Improving State of the World. Washington, Cato Institute, 2007, pp. 303-309.
[20] Sherwood B. Idso, “Carbon dioxide and global change.” Rational Readings on Environmental Concerns, Jay H. Lehr, ed. New York: Van Nostrand Reinhold 1992, p. 422.
[21] IPCC 2001, Chapter 3, Section 3.2.2.4, p. 195. See also IPCC 2007, Working Group III, Chapter 3, Section 3.2.1.6, “Land use change and land use management.”
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Life can survive a variation of 10°C in one day between night and day.
Life can survive a variation of 10°C in one year between winter and summer.
Life can survive a variation of 10°C in 100 000 years between a glacial period and an interglacial.
Life can survive a variation of 10°C in 10,000,000 years between an icehouse and greenhouse.
But what about 2°C in 100 years? I would like to see a proof that life would not survive that.
About the economy, A rise of 10 meters of sea levels would probably destroy the economy just as much as earthquakes have destroyed California’s economy in the last century.
Pretty tough to go back to the Miocene with the current tectonic plate confit. Lo, we’re doomed to the ice.
Confit -> config. All thumbs here.
Greenland is not looking good
http://science.nasa.gov/science-news/science-at-nasa/2012/24jul_greenland/
Steven Mosher,
Greenland looks fine to me.
Warmer is better. Cold kills.
Steven Mosher says:
July 24, 2012 at 11:26 am
Greenland is not looking good
http://science.nasa.gov/science-news/science-at-nasa/2012/24jul_greenland/
“On July 8, 40% of the ice sheet’s surface had melted”.
——————————————-
Modis Terra shows daytime highs of -8C to -25C on July 8 on the ice-sheet.
http://neo.sci.gsfc.nasa.gov/Search.html?group=19
Weather Underground for the last month from the Summit Greenland weather stations. Some brief periods up to 0.0C.
http://www.wunderground.com/cgi-bin/histGraphAll?day=24&year=2012&month=7&ID=04416&type=1&width=614
Two obvious points in response. First, the author seems to agree with the alarmists that a rise in CO2 levels of a few hundred parts per million (0.000003) could have a dramatic effect on climate … and we all know that can’t be true. Second, humans really weren’t thriving during the Miocene, and certainly not 7 billion of them who need land to grow food and live.
“Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time,” says Lora Koenig, a Goddard glaciologist and a member of the research team analyzing the satellite data. [source]
Followed by the obligatory scare quote:
“But if we continue to observe melting events like this in upcoming years, it will be worrisome.”
Don’t you get tired of all the fake alarmism? It’s all bogus. The Null Hypothesis shows that there is nothing to be worried about. It’s all happened before, and to much greater extremes. Relax, runaway global warming’s not gonna getcha.
Buzz B says: “the author seems to agree with the alarmists that a rise in CO2 levels of a few hundred parts per million (0.000003) could have a dramatic effect on climate”
Such an inference may or may not be correct but it is not really possible to be certain of that from what has been written. The author merely notes that there were times in Earth’s history when there was a) more CO2 in the atmosphere and b) the climate was much warmer than the present. The author might personally believe this indicates that those periods were as warm as they were mostly due to that CO2, or possibly not. I certainly wouldn’t jump to that conclusion: certainly those climates would have been colder than they actually were if CO2 levels had been lower, but that doesn’t mean that the entire temperature difference between today and then was due to that CO2. The distribution of the continents was different, changing ocean circulation, and often there was a lack of landmass over the Southern Pole. There may have been different amounts of other greenhouse gases, the variations in cosmic rays due to passage of the spiral arms of the galaxy might be important as could variations in some of the Earth’s orbital parameters. It’s possible that the atmospheric aerosol or dust loading was very different from the present, from variations in volcanic activity, say. There are many, many possible factors which might be involved in paleoclimate variations. Without know what role those other factors played it is impossible to determine what quantitative effect from CO2 was present.
@LazyTeenager says:
“So americans will have to grow and eat rice instead of wheat or corn.
“And goodbye to Florida.”
Which will turn into a huge, productive fishing ground. Ditto the E Coast.
Re Greenland surface melting:
I looked in the report for a volume of water released by the melting but it was conspicuously absent. It would be very odd if, during midsummer’s constant sunshine, there was no melting of the top skin of the ice cap.
Since 1889 you say? Wasn’t that the year the Arctic’s NW Passage was open and it was possible to sail up the west side of Greenland? Too bad it was followed by 30 years of cooling. Fortunately that was followed by 30 years of warming which was followed by 30 years of…
Does anyone see the disconnect between the ideal of a lush tropical paradise and the western forest fires and drought-stricken midwest today? Or has it just not heated up enough to get wet?
If only. Our modern climate regime alternating between glacial (90-100k years) and interglacial (10-20k years) will not be altered in any way by man. It’s a nice dream, though.
Mark:
Isthmus of Panama closed around 3 mya, not 16 mya, an event which helped precipitate the Pleistocene glacial epoch, still on-going despite calling our present interglacial episode the Holocene, by interrupting tropical oceanic circulation.
http://earthobservatory.nasa.gov/IOTD/view.php?id=4073
Re: Buzz B and timetochoose again
I emphatically don’t think these geological eras were warmer due to carbon dioxide, but due mainly to ocean and air circulation patterns that favored warmth. The closing of the Panama isthmus and mountain-building were the main causes of the current ice age, in my view.
My post argues that if the CAGW/carbon dioxide theory was valid–I don’t think it is but if–would the result be catastrophic? Even in a worst case scenario, really high sea levels, the answer is no. To say otherwise is to ignore 50 million years of planetary history. 🙂
It would be a shame to lose Florida, but looking at the Miocene map it looks like Scuba diving opportunities will be a lot better for those of us living in Atlanta. Pity I have to wait a thousand years for it — I suspect by then my Social Security benefits will have run out.
I’m with Fredb, “tropical everywhere” sounds like a nightmare to me: Hot, humid, stuff growing everywhere, mold, nasty bugs, insects and reptiles. I’ve been to gulf coast of the US, in deep winter it’s so-so, the rest of the year it’s my idea of hell.
I’ll live with 4-6months of deep freeze winter to avoid a summer that’s like a steam bath.
This really is The Age of Stupid.
Sceptics attack the science on the grounds that the link between CO2 and temperature is weaker than calculated – or does not exist at all.
Then global warming is accepted but dismissed because its all OK as our descendants will live in a “tropical paradise” as it was tens of millions of years ago.
Big problem with that theory. Tens of millions of years ago there were no humans, no cities, no farmland.
If proponents of Paul MacRae’s complacency see it as a good thing, tell us how do we defend the major cities of the world from major sea level rise ? Its no good saying its centuries away – future generations will not thank us for flooding their cities and not caring.
And what about the vast numbers of low lying smaller coastal settlements around the world and the productive farmland that supports them. Where do those millions of people go ?
If you live in a densely populated low lying area like we do – areas which have struggled for centuries to hold back the sea, areas that have seen thousands die from coastal flooding in living memory, then major sea level rise is not talked of as an idle bit of speculation.
Add me to the list of those living in the tropics who disagree with Fred, ISTM that the only people who think like him are those who have never tried it.
That may be understandably true, but for those that live and build on flood plains… What exactly do you expect over future centuries?! GK
“hippopotami gamboling in the Thames”
Mud, mud, glorious mud …
Thats odd. The link seems to have vanished. I’ll break it up and see if it survives.
http://
http://www.youtube.com/
watch?v=kN0WPwFD9is
RE: Bruce Cobb says:
July 24, 2012 at 1:55 pm
If only. Our modern climate regime alternating between glacial (90-100k years) and interglacial (10-20k years) will not be altered in any way by man. It’s a nice dream, though.
================================
Indeed it is. And beyond that, it is the ultimate denialism. Denying the eventual end of the interglacial is the ultimate denial. I can sort of understand why, since the consequences of that looming event are so dire.
LazyTeenager says: So americans will have to grow and eat rice instead of wheat or corn.
Why? Wheat and corn are tropical plants, Einstein. Ever been to Iraq’s Fertile Crescent? I’m guessing not. Or the Yucatan? That’s where those plants were domesticated. It’s hotter there than here, and was even more so when those plants were first cultivated. Am I typing too fast for you? Do you really think that wheat and corn won’t grow in the Midwest if it were warmer? Why? You’re not a farmer, are you? Ever planted anything?
Oh my, the sea level cities will flood in 250 years. What ever will we do?
Answer: the really slow people will probably drown, the ones that can’t outrun a snail. Everybody else will move uphill. It’s happened before. Sea level ports of 2,500 years ago are underwater today, but guess what? The residents moved uphill rather than standing there immobile for 250 years while the water got deeper and deeper.
The dire reports from warming (if it were to happen) are baseless drivel. As author MacRae points out, WARMER IS BETTER.
If we have anything to fear climatically, it is the pending return of the next Pleistocene glaciation, with two mile thick continental ice sheets and all that entails. You can’t grow wheat, corn, or rice on an ice sheet.
tty,
Quoting an abstract Frakes et al:
“Three zones can be identified for the Early Cretaceous climate of eastern Australia: (1) a very cold southern region, at latitudes above about 72 ° S, characterized by meteoric waters possibly originating as Antarctic glacial meltwaters; (2) a zone of strongly seasonal climates, with freezing winters and warm summers, between about 72° and 53° S. Lat.; and (3) a mid-latitude zone (below about 50° S. Lat.), where freezing temperatures were not common. However, owing to scant biostratigraphic control on the successions, the time span of specific climates in both the cold and the seasonal zones cannot be determined and probably existed only for short intervals.”
A twenty degree latitude shift in climate zones seems pretty cozy to me. Some of the proposed “glaciations” are inferred from sea level drops and unsorted sediments off the continental shelves. I would argue for tectonic causes, elevated midocean ridges form rapid spreading, emplacement of large igneous provinces.
I’ll give you the tillites, but above latitude 72 nothing would surprise me.
65 million years ago the Atlantic was just beginning to become an ocean. The Pacific was correspondingly much bigger. So, the whole energy balance of the planet was completely differnt from what it is today because of the different distribution of land masses. This alone can explain the temperature difference. For instance, there was no land mass at either pole, hence no place where land ice could accumulate. Therefore, if there was any ice at all, it was as sea ice. This means that the sea level observed then is the maximum that can be realised by the given quantity of water on the surface.