Noah’s Arc Revisited

June 11, 2009




Andrew Glikson

Earth and paleoclimate scientist

Australian National University


Mammals have only been able to attain large dimensions on land once atmospheric CO2 concentrations declined toward c. 500 ppm during the Eocene (56-34 million years ago) (, with related cooling of c.5 degrees C, formation of the Antarctic ice sheet and decline of sea levels by c.70 meters. current atmospheric carbon gas levels (CO2 – 387 ppm; CO2+CH4 >450 ppm equivalent) threaten fast-tracking toward the top of ice age conditions.

( ; ;

DOI: 10.1126/science.1059412 ; doi:10.1038/nature06588 ; ;;292/5517/686 ;

In the wake of current global warming to temperatures as high as 4 – 6 degrees C, humans, having endured the sharp climate upheavals of the Pleistocene glacial-interglacial cycles (+5 degrees Celsius; 120 meter sea level rise), are likely to survive in sheltered environments, including clouded tropical mountain valleys, high elevation islands and sub-Arctic latitudes.

Under global warming on the scale of several degrees Celsius, the future of civilization, hinging on extensive agriculture in temperate climate zones prone to severe droughts, on cultivation in low river deltas prone to sea level rise, and on irrigation of mountain snow-fed rivers, is less clear.


The progression of global warming through warm/cold pulsations ( (Fig. 2A) and related climate projections (Fig. 2B), in part associated with the ENSO cycle and the sun spot cycle, allows sceptics to advance false hopes of “global cooling”, which affect the pressure for deep cuts in carbon emissions and development of alternative clean power utilities.  Few scientists endeavor to communicate the realities of accelerating climate change, and those who do discover governments hardly listen, proceeding with policies guided by anything but the latest evidence. Unfortunately:

1. Current climate change is now exceeding the maximum natural greenhouse radiative forcing level of the last 2.8 million years by 38% based on CO2 alone (387 ppm) and by 53% based on CO2+methane (450 ppm CO2-equivalent). Up-to-date studies define the upper atmospheric forcing limit of the Antarctic ice sheet at about 500 ppm CO2. Due to carbon cycle feedbacks and ice/water interaction feedback, this threatens accelerated collapse of polar ice and rapid meter-scale sea level rises within time frames shorter than originally projected by the IPCC, as reported by Hansen et al. 2008 and 2007 (

2. The threat of irreversible tipping points in the climate system is more urgent than has been envisaged by the IPCC-2007 Report, as indicated by Lenton et al., 2008 ( and recent studies of the vulnerability of the atmosphere and ice sheets during the most recent history of the Earth (Steffensen et al., 2008) (;1157707v1?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=J.P.+Steffensen&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT).

3. In view of the cumulative long residence nature of CO2, reduction of emission is no longer sufficient to avert positive Carbon feedbacks, notably release of methane from permafrost and from bogs, with consequent climate runaway process.

4. Based on the above, Hansen et al. 2008 indicate the maximum CO2 level allowable should be defined at 350 ppm. As this level has already been exceeded, to avert climate crisis, every effort should be made to develop rapid CO2 atmospheric draw-down technology, such as already exists in principle, including chemical capture and fast-growing CO2-sequestering vegetation. CO2 being a cumulative long-residence time gas, the latter may be unable to mitigate global warming to extents illustrated in Figure 2B.

Figure 2A. Irregular progression of global warming correlated with the ENSO (El Nino – La Nina) cycle and sun spot cycle. (Easterling and Wehner, 2009, Is the climate warming or cooling, Geophysical Research Letters, v. 36, L08706, doi:10.1029/2009GL037810, 2009)  ( /2009GL037810.shtml)

Figure 2B. One realization of the globally averaged surface air temperature from the ECHAM5 coupled climate model forced with the SRES A2 greenhouse gas increase scenario for the 21st century. (Easterling and Wehner, 2009, Is the climate warming or cooling, Geophysical Research Letters, VOL. 36, L08706, doi:10.1029/2009GL037810, 2009)   (



Nothing could result in a greater collective sigh of relief had it been shown current global warming is a transient anomaly or, in the very least, not caused by humans. Such a discovery, once verified, would have resulted in more than one Nobel Prize.

The difference between ambit claims and science being a meticulous review and verification system, by choosing non-scientific media platforms, repeating the same long-discarded arguments ad-infinitum, and not facing to direct debates, the sceptics’ approach amounts to a rejection of the scientific method. The latest example is Plimer’s the book “Heaven and Earth” ( and related media articles.

A long road leads from Galileo, persecuted by the Church for unearthing a new truth, to sceptics obtaining backing from a Cardinal (“Climate Change pauses” by Cardinal George Pell. archbishop/stc/2009/2009524_ 1018.shtml).  It is a wonder how a scientist who fought creationism tooth and nail (, and a cardinal reported to be “comfortable with intelligent design” ( find themselves in the same camp denying human-driven global warming.

Having spent years trying to refute an alleged discovery of relics of Noah’s Ark relics on Mount Ararat ( (Figure 3), a story echoing sea level rise associated with increased temperatures (c.1 degrees Celsius) in the early Holocene (c.10,000-6000 years-ago) (, Plimer questions the post-19th century acceleration of sea level (from 0.11 to 0.35 cm/year) which is consistent with global temperature rise of more than 0.8 degrees C ( Once account is taken of (A) the masking effect of industrial short-lived aerosols, and (B) albedo reduction of the Arctic Sea ice and other parts of the cryosphere, radiative forcings since 1750 approach the equivalent of near-1.5 degrees C (

In an attempt to negate the critical role of over 305 billion tons of emitted carbon during the 19th – 21st centuries, Plimer questions the established relations between the carbon gases and climate through time, demonstrated by multi-proxy studies ( ;

DOI: 10.1126/science.1059412 ; doi:10.1038/nature06588 ;, and further suggests a supposedly beneficial nature of current rise of CO2 and temperature (,25197,25552775-7583,00.html ;,25197,25429080-7583,00.html).

Many of the questions raised by Plimer are answered in the comprehensive synthesis of peer-reviewed geological and paleo-climate literature of the IPCC AR4 2007 report, which states (

Climate has changed on all time scales throughout Earth’s history. Some aspects of the current climate change are not unusual, but others are. The concentration of CO2 in the atmosphere has reached a record high relative to more than the past half-million years, and has done so at an exceptionally fast rate. Current global temperatures are warmer than they have ever been during at least the past five centuries, probably even for more than a millennium. If warming continue unabated, the resulting climate change within this century would be extremely unusual in geological terms. Another unusual aspect of recent climate change is its cause: past climate changes were natural in origin (see FAQ 6.1), whereas most of the warming of the past 50 years is attributable to human activities.”

Plimer rejects the IPCC (“The IPCC process is related to environmental activism, politics and opportunism. It is unrelated to science” ( , p. 20).  He further dismisses climate scientists despite hundreds of their peer-reviewed papers, for example where he states: “No evidence is provided for this statement and no signatory to this letter has published anything to support this claim” (,25197,25552775-7583,00.html ;,25197,25429080-7583,00.html) ( Plimer claims “No critic has argued science with me. I have just enjoyed a fortnight of being thrashed with a feather” but has not to date responded in any detail to critiques of his book, i.e. by Enting, Brook, Vernon, Ashley, Sandiford (,25197,25552775-7583,00.html,25197,25429080-7583,00.html)

To bring examples of only a few points in the debate (Plimer is cited in inverted comas):

1.      “So depleted is the atmosphere in CO2, that horticulturalists pump warm CO2 into glasshouses to accelerate plant growth.”  The greenhouse glasshouse analogy is irrelevant as plants need to be constantly watered in these artificial environments  ( as distinct from open space agriculture and habitats. Plimer overlooks the fact that CO2 levels of the atmosphere, which oscillated between 180 and 280 ppm since 2.8 million years ago, are inherent in the natural environment in which current biodiversity and humans have evolved.  The sharp departures from the maximum atmospheric composition of 280 ppm of the last 2.8 million years to 387 ppm is leading mid-Pliocene-like conditions with temperature rise of 2-3 degrees C leading to sea level rise by 25+/-12 meters ( ;

2.      “Carbon dioxide is an odourless, colourless, harmless natural gas. It is plant food. Without carbon, there would be no life on Earth“. Here Plimer makes two cardinal mistakes:

(A)   Once the balance of atmospheric composition changes, as it has through geological times, plants and organism adapt, but only over extended time periods. Sharp changes, as induced by volcanic, impact or greenhouse crises, lead to mass extinction of species (  ; ; ;

(B)   The current rise in CO2 of c.2 ppm/year and of temperature (c.0.017C/year) by about an order of magnitude faster than the mean rise during the last glacial termination (c.0.002C/year) and faster than the 55 Ma greenhouse extinction event ( threatens similar consequences as the latter event.

3. “The main greenhouse gas has always been water vapour. Once there is natural global warming, then CO2 in the atmosphere increases.” ((,25197,25552775-7583,00.html ;,25197,25429080-7583,00.html). The opposite is the case: Whereas carbon gases have a long residence time and may be derived from buried geological sources, water vapor constitutes transient feedback. Thus, water vapor occur at very low concentrations over the fastest warming parts of Earth, namely the polar regions and deserts.

4. “Ice cores show CO2 increases some 800 years after temperature increase so why can’t an increase in CO2 today be due to the medieval warming (900-1300)?”  According to the IPCC-2007 4AR report mean global temperatures during the Medieval Warming Period were less than 20th century warming ( ; p. 469). The post-industrial increase in CO2 of over 40% the maximum of Pleistocene interglacial periods is clearly related to the industrial emission of over 305 billion tons of carbon and can not be compared to the medieval warm period, during which no anomalous CO2 rise is recorded ( ; Fig 6.4]).  The lag of CO2 rise behind temperature during glacial terminations is related to the dominant role of forcing by ice melt/water interaction followed by CO2 feedbacks from warming oceans and drying vegetation (

5.      “Some 85 per cent of volcanoes are unseen and unmeasured yet these heat the oceans and add monstrous amounts of CO2 to the oceans. Why have these been ignored?”  Not so. Comparisons between the St Helens (1980), El-Chichon (1982), Pinatubo (1991, 93) and other eruptions and the Mauna Loa atmospheric CO2 trend ( display no marked signatures of these volcanic eruptions.

6.      “Why have there been five significant ice ages when CO2 was higher than now?”  The atmospheric CO2 range during the Oligocene – Holocene range, measured from proxies (stomata fossil plant pores, carbon and boron isotopes, sodium minerals, alkenones), indicate CO2 levels below 500 ppm ( ; doi:10.1038/nature06588). Previous ice ages include Jurassic, Carboniferous-Permian and Devonian glaciations with CO2 a few hundred ppm ( ;  DOI: 10.1126/science.1059412 ; doi:10.1038/nature06588 ; Studies of Ordovician paleoclimate remain inconclusive in this respect

7.      “Computer models using the past 150 years of measurements have been used to predict climate for the next few centuries. Why have these models not been run backwards to validate known climate changes?” Not so. Extensive climate modeling has been conducted on past climate changes, for example of the mid-Pliocene by the USGS ( ;

8.      “I would bet the farm that by running these models backwards, El Nino events and volcanoes such as Krakatoa (1883, 535), Rabaul (536) and Tambora (1815) could not be validated.”  Climate projections do not include the effects of earthquakes or volcanic eruptions, nor do they need to as volcanic aerosol effects are short term, whereas the volcanic CO2 effect is relatively minor.

9.      Several examples have been presented of inconsistencies between diagrams included in “Heaven and Earth” and original data sources (

In praising the “merit” of global warming, Plimer overlooks the causes of past mass extinction of species, triggered by environmental changes at a pace with which organisms could not cope. These included large-scale volcanic eruptions, asteroid impacts and runaway methane release, such as occurred at 55 million years ago ( ; doi:10.1038/nature06588).


the On the 15th June, 2009, Senator Steve Fielding, leader of “Family First”  will cast a vote deciding whether the Australian government is allowed to take a first tentative step, be it woefully inadequate, to honor its election commitment of “the highest moral issue of our times (,,25037352-7583,00.html?from=public_rss).

Fielding is undertaking his own “open mind” “exploration” of climate science. ( ;  Never mind that top climate research institutions world-wide (Hadley-Met, Tyndale, GISS-NASA, Potsdam, CSIRO, BOM, NSIDC) have already concluded dangerous human-driven climate change is tracking toward mean temperatures of +2, +4 and even +6 degrees C ( (Figure 2B).

Straight out of meetings at the Heartland Institute, supported by the American Enterprise Institute, which received $1,625,000 from Exxon-Mobil between and 1998 and 2005 (, Fielding states “So far I don’t think there’s been a real debate about the science” and “Let’s actually explore that“.  Can it be that Senator Fielding’s “exploration” may in anyway be affected by his view of the Greens, expressed as “The Greens are in the extreme camp and like any fanatical group, they’re locked into ideology” (,21985,25585267-661,00.html).

Following in the footsteps of Cardinal George Pell who, for several years, has been referring to environmentalists as “Scaremongering” and “zealots” (, with “hysteric and extreme claims about global warming are also a symptom of pagan emptiness” (, stating: “The science is more complicated than the propaganda“.

Setting themselves as arbiters of science, assuming the role ancient Egyptian priests in predicting the flow of the Nile, the rains, solar and lunar eclipses, with one exception: The Egyptian priests conducted their own astronomical and water level measurements.

Fielding states “They (the “skeptics”) have actually got models that show that the solar energy, in other words, the energy from the sun has a higher direct link with global temperatures than carbon emissions. And this is going back, not only over the last 10 years, but hundreds of years” (

In his climate “exploration” Fielding may not be aware that since the mid-20th century the role of the sun was limited to the 11 years sunspot cycle, oscillating at +/- 0.1 degrees Celsius. (, compared to mean temperature rise due to greenhouse warming of about +0.6 degrees Celsius ( ; Stateing “And they were putting forward some science and some evidence and some facts that were questioning whether CO2 is actually driving global warming.” (, nor does he appear to be aware of the basic physics and chemistry of the infrared greenhouse effect (

D.  Conclusions

  1. Currently the atmosphere is tracking toward conditions of the Pliocene, c.2.8 million years ago, when CO2 levels of c.400 ppm and temperature rises of 2 to 3 degrees led to sea level rises of c.25+/-12 meters.
  1. With open-ended carbon emissions, the rise of temperature at experimentally determined climate sensitivity rates (3+/-1.5 degrees C per doubling of CO2 levels) ( can only result in a shift in the Earth’s climate state to pre-ice age conditions, including major sea level rise, akin to conditions during which the dinosaurs thrived for 200 million years, a period three orders of magnitude longer than “sapiens”.
  1. A well financed alliance of neoconservatives, fossil fuel executives, ex-tobacco lobbyists (, fundamentalists, right wing journalists and sceptics who operate outside the scientific peer-review system, receiving near-exclusive publicity in large parts of the media, disseminate untruths and doubt which are welcome by (A) those of prefer to live in denial of dangerous climate change; (B) those who would not understand the scientific method; and (C) provide governments with excuses to delay weak 11th hour attempts at carbon constraints.
  1. The motivation of those who continue to disseminate dangerous untruths which can only result in the continuous rise of atmospheric CO2 levels and temperatures, shifting the atmospheric state during which humans evolved over the last 2.8 million years, defies contemplation

Having endured the sharp climate upheavals of the Pleistocene glacial-interglacial cycles, humans are likely to survive in suitable environments, including clouded tropical mountain regions, high elevation islands and cool high latitudes regions. Hinging on extensive agriculture in temperate climate zones, prone to severe droughts, on cultivation in low river deltas, prone to sea level rise, and on irrigation of mountain snow-fed rivers, the future of civilization under global warming on the scale of several degrees Celsius is less clear.

Figure 3. “Noah’s Ark”. Mount Ararat area.

Dr. Andrew Glikson is a Earth and paleo-climate research scientist at Australian National University. He spends much of his free time invested in efforts to address climate change issues in a timely fashion and can be contacted at:

Dr. Andrew Glikson is a regular columnist for

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