Erroneous Lessons from Earth's Past

Climate alarmists have been slow to learn that their over-reliance on computer models and unproven theories has harmed their public credibility. In an attempt to counter the richly deserved bad press that climate science has been garnering these days, a number of global warming true believers are trying a different, more fact based approach to scaring the public. One such attempt recently appeared in the journal Science—not as a paper describing original research but as a perspective article. In it, a Senior Scientist at the National Center for Atmospheric Research, in Boulder, Colorado, attempts to “weave together” some carefully selected “threads in the discussion of climate” to arrive at a very familiar and unconvincing conclusion.

In the perspective article “Lessons from Earth's Past,” Jeffrey Kiehl, an atmospheric scientist by training, tries his hand at constructing a case for modern day global warming based on carefully chosen ancient historical “facts.” Some of the supporting arguments are based on outdated notions and some are just plain wrong. The first paragraph offers a hopeful start:

Climate models are invaluable tools for understanding Earth's climate system. But examination of the real world also provides insights into the role of greenhouse gases (carbon dioxide) in determining Earth's climate. Not only can much be learned by looking at the observational evidence from Earth's past, but such know ledge can provide context for future climate change.

What a concept! Who would have thought that—“invaluable” climate models aside—scientists can actually learn something by studying the physical world around them? Not only can insights be gained from actually looking at the system being studied, examining how that system reacted to changing conditions in the past may be useful in making projections about the future. One might almost suspect that climate change alarmists were turning into real scientists. But then the article descends into false argument and supposition.

After first asserting that human use of fossil fuels will soon drive atmospheric CO2 levels to 1000 ppm or higher—not entirely a foregone conclusion—Kiehl then attempts to establish an equivalence between Earth's climate 35 million years ago and that projected for 2100. That equivalence is based solely on CO2. To arrive at this equivalence Kiehl embeds a mistruth of gigantic proportions in his explanatory logic:

What was Earth's climate like at the time of past elevated CO2? Consider one example when CO2 was ∼1000 ppmv at ∼35 million years ago (Ma). Temperature data for this time period indicate that tropical to subtropical sea surface temperatures were in the range of 35° to 40°C (versus present-day temperatures of ∼30°C) and that sea surface temperatures at polar latitudes in the South Pacific were 20° to 25°C (versus modern temperatures of ∼5°C). The paleogeography of this time was not radically different from present-day geography, so it is difficult to argue that this difference could explain these large differences in temperature. Also, solar physics findings show that the Sun was less luminous by ∼0.4% at that time. Thus, an increase of CO2 from ∼300 ppmv to 1000 ppmv warmed the tropics by 5° to 10°C and the polar regions by even more (i.e., 15° to 20°C).

Hidden within the obscuring blizzard of temperatures and ppmv readings there lies a false statement that invalidates the remainder of the article. The intentionally misleading statement, highlighted in the quoted text above, claims that the physical configuration of the world was effectively no different 35 million years ago than today. This is a blatant lie. Paleontologists know very well how different the geological configuration of the world was back then, because the slow geological changes since then transformed a hot-house world into an ice-house one. Indeed, the story of climate during the Cenozoic (65 mya to the present) has been, after a brief warm spell during the Middle Eocene Climatic Optimum, a long march into frigidity, culminating with the Pleistocene Ice Age.

The fact of the matter is that the world 35 mya was noticeably different in its geography than the globe today. Granted, the general outlines of the modern continents are present, but there are several important differences. The image below shows a reconstruction of Earth as it appeared at the end of the Eocene, 35 million years ago.

Earth 35 million years ago.

Compare the planet shown above with Earth today:

Earth today.

These and other exquisite paleogeographic maps by Ron Blakey are available from NAU Geology. From them can be gained a sense of just how radically Earth has changed over geologic time. While the differences between the two maps may seem subtle, they are indications of important geographic variation:

  • North and South America were not connected, allowing water from the tropical Pacific and Atlantic to mingle. The Isthmus of Panama had yet to form and South America was closer to Antarctica.

  • Because South America and Australia were closer to Antarctica, the circumpolar circulation had yet to form.

  • The Tethys Sea was not yet fully closed by the collision of Africa with Eurasia, allowing water to pass from the Indian Ocean to the Atlantic.

  • The Atlantic Ocean was much narrower, perhaps half the width it is today. This affected ocean circulation and global heat distribution.

  • The deep-water Indo-Pacific gateway, though significantly narrower than at the beginning of the Cenozoic, still allowed deep currents to flow between the Pacific and Indian oceans.

  • The deep ocean currents were exceptionally warm, meaning that the ocean already had accumulated a large store of heat energy.

  • There were no permanent glacial ice sheets. Permanent ice sheets were just beginning to form on Antarctica and, eventually, Greenland.

  • The Himalayan plateau was just being formed, due to the collision of India with the Asian mainland. As the Himalayan peaks rose to their present height, changes in atmospheric circulation took place. In Europe, the Alps had just finished their uplift as well.

  • Modern grasses evolved, forests shrank and grasslands expanded, changing ground cover characteristics.

The most important single event since the warmer climes of the Eocene was the formation of the circumpolar current around Antarctica. The Tasmanian Seaway, which separates East Antarctica and Australia, opened to water circulation around 33.5 Ma. The timing of the opening of the Drake Passage, between South America and the Antarctic Peninsula, is not as well dated but the current had certainly formed by 20 mya. Oceanic models have shown that the opening of these two passages limited polar heat convergence and caused a cooling of sea surface temperatures by several degrees.

And while mentioning ocean water temperatures, the pre-global cooling SST estimates used by Kiehl are extremely high. Fredrik P. Andreasson and Birger Schmitz, reported in the April 2000 GSA Bulletin: “Oxygen isotope profiles of shells from Texas and Mississippi suggest a seasonality of 8–9°C along the early middle Eocene U.S. Gulf Coast, with a winter temperature of 19°C and a summer temperature of 27–28°C.” Far less than the 35-40°C presented in the perspective article (for more information about conditions during the middle Eocene see “CO2 & Temperature During The Middle Eocene Climatic Optimum”).

The circumpolar current did not flow during the Eocene.

The eventual closing of the Tethys Sea and the formation of the Isthmus of Panama, linking North and South America and separating the Atlantic and pacific oceans, also helped reconfigure global ocean currents. And it is the circulation of ocean water that redistributes the majority of the world's heat energy.

The climatic isolation of Antarctica went hand in hand with the formation of the first permanent ice sheets on that continent. These were eventually to turn into the large mass of glacial ice that caps the south pole region today. As the glacial ice increased, sea-levels dropped altering coastlines and further changing ocean circulation patterns. The addition of large ice sheets also altered Earth's albedo, further cooling the planet. This albedo change is part of a natural feedback loop, as is the varying amount of CO2 in the atmosphere.

The comparison between human emissions and the massive injection of atmospheric carbon that coincided with the PETM is also improper. During the PETM, the the level of CO2 rose by 3000-4000 ppm (some estimates go as high as 10,000 ppm). But they started at 1000 ppm, a level three times as high as the “pre-industrial” level that climate alarmists seem to think is the optimum level. It should be noted that CO2 levels below 300 ppm are proper—for a glacial period.

Climate development from the early Cenozoic greenhouse to the late Cenozoic icehouse world

Furthermore, the pulse of CO2 (or CH4) that caused the PETM was removed from the atmosphere quite rapidly, taking on the order of 20,000 years. In fact, a recent paper states that the ecosystem accelerated its rate of carbon sequestration in response to the PETM release (see “Rapid carbon sequestration at the termination of the Palaeocene–Eocene Thermal Maximum”). Though a massive PETM like release of CO2/CH2 can cause a rise in global temperatures, such a rise is only a perturbation of the system that is quickly corrected.

It has long been known that long-term climate change—change on time scales of millions of years—is caused by Earth's changing geography. Medium-term change is regulated by cyclic changes in Earth's orbital parameters—the Milankovitch cycles. Rapid change is caused by what Zachos et al. called aberrations: volcanoes, asteroid impacts, and sudden releases of previously sequestered carbon. Together, these “trends, rhythms and aberrations” are what cause climate change.

All of the factors outlined above clearly point to the fact that geological forces, operating over tens of millions of years, caused Earth's climate to cool dramatically during the past 35 million years. Claims that the cooling was caused by a reduction in atmospheric CO2 have been refuted by many. Studies of the Late Ordovician glaciation found that, without orbital forcing, ice sheets can grow with CO2 levels as high as 10 times preindustrial atmospheric level. Yet Kiehl maintains this fiction to the end, even to the point of reintroducing claims based on computer models. Here is how his perspective concludes:

The above arguments weave together a number of threads in the discussion of climate that have appeared over the past few years. They rest on observations and geochemical modeling studies. Of course, uncertainties still exist in deduced CO2 and surface temperatures, but some basic conclusions can be drawn. Earth's CO2 concentration is rapidly rising to a level not seen in ∼30 to 100 million years, and Earth's climate was extremely warm at these levels of CO2. If the world reaches such concentrations of atmospheric CO2, positive feedback processes can amplify global warming beyond current modeling estimates. The human species and global ecosystems will be placed in a climate state never before experienced in their evolutionary history and at an unprecedented rate. Note that these conclusions arise from observations from Earth's past and not specifically from climate models. Will we, as a species, listen to these messages from the past in order to avoid repeating history?

Note that Kiehl's conclusions are not “specifically” from climate models, but rather based on flawed observation. There is no proof supporting the existence of “positive feedback processes” that will drive Earth to thermal ruin—Earth has been much warmer before, with much higher CO2 levels, and its climate did not experience runaway global warming. Will we, as a species, learn our lesson? What fatuous tripe.

The paleogeography of late Eocene Earth was visibly different than Earth today, and even more significantly different in terms of its effect on climate. The truth of the matter is that Earth, as it existed 35 mya, is gone and will never return. The planet we inhabit is not the same or even very similar to that vanished world. Kiehl's specious assertion to the contrary is not just wrong, it is deceptive.

The Earth of 35 million years ago is gone, never to return.

That a senior scientist like Kiehl, working in the field of climate science—specializing in “understanding Earth’s warm greenhouse climates for deep past time periods ranging between 300 to 50 million years ago”—could be ignorant of our planet's ever changing geology is beyond incredulous. And ruling out incompetence leaves only mendacity. Efforts to prop up the discredited theory of CO2 driven anthropogenic global warming without the support of computer models fall far short. Take away their bogus climate models and promoters of global warming are left only with lies and half-truths.

Be safe, enjoy the interglacial and stay skeptical.



OK, but please look up the word "incredulous". It isn't a synonym for incredible


Incredulous means unwilling or unable to believe; doubting; skeptical; showing doubt or disbelief. The phrase "beyond incredulous" means beyond disbelieving or beyond withholding of belief. One might find it incredulous that a senior scientist would make such a statement. I'm claiming that, in this case, it is beyond incredulous, that incredulity is not an option. In other words, his knowing that his statement was false was beyond doubt. If I had meant incredible I would have used incredible.

Formation of Isthmus of Panama

According to “Closure of the Central American Isthmus and its effect on deep-water formation in the North Atlantic” by Kevin W. Burton, Hong-Fei Ling and R. Keith O'Nions, the Isthmus of Panama didn't form until 3-4 million years ago. They do say that the isthmus' formation did impact modern circulation patterns. The timing looks just about right for the onset of the Pleistocene Ice Age.

Paper's abstract:

    Modern ocean thermohaline-driven circulation influences global climate by transporting heat to high latitudes and by affecting the exchange of CO2 between ocean and atmosphere. North Atlantic Deep Water (NADW) plays a key role in this circulation, and Quaternary climate cycles have been linked to changes in NADW flow4. General circulation model simulations indicate that before closure, some 3–4 million years ago, of the Central American Isthmus—the narrow strip of land linking North and South America—the direct flow of low-salinity water from the Pacific to the Atlantic Ocean would have led to a smaller NADW flow. Sedimentation patterns and nutrient proxies support these model results by indicating an increase in NADW flow around the time of isthmus closure, but these records do not allow changes in different NADW sources to be distinguished, and the overall effect of closure on global ocean circulation is poorly known. Here we present Nd, Pb and Sr isotope records preserved by a hydrogenous ferromanganese crust from the NADW flow-path in the western North Atlantic Ocean. These records indicate that the isotopic signal associated with NADW strengthened around 3–4 million years ago showing that deep water that formed in the Labrador Sea made a gradually increasing contribution to NADW flow. These data, taken together with those from the central Pacific Ocean, indicate an increased NADW flow since isthmus closure, and suggest that the closure established today's general pattern of ocean circulation.


Dear Doug Hoffman

I was wondering if, in your links to other climate skeptic websites, you could give a link to the website Climate Change Dispatch

I've been emailing the owner of that website recently and helped him to improve the 'Temperate Facts' section. I think the site is now better than it was before.

I asked him to give a link to Resilient Earth in his links section, and he's done that

So, anyway I'd appreciate it if you did add CCD to the links section of your site.



PS: Great article.


The link has been added and thanks for spreading the word about The Resilient Earth.