Paul MacRae, June 24, 2008

Most geologists aren’t part of Al Gore’s “100 per cent consensus” of scientists that humans are the principal cause of global warming and that we have to take drastic steps to deal with it.

For example, in March 2008, a poll of Alberta’s 51,000 geologists found that only 26 per cent believe humans are the main cause of global warming. Forty-five per cent believe both humans and nature are causing climate change, and 68 per cent don’t think the debate is “over,” as Gore would like the public to believe.1

The position of the American Association of Petroleum Geologists is quite clear:

The earth’s climate is constantly changing owing to natural variability in earth processes. Natural climate variability over recent geological time is greater than reasonable estimates of potential human-induced greenhouse gas changes. Because no tool is available to test the supposition of human-induced climate change and the range of natural variability is so great, there is no discernible human influence on global climate at this time.2

Why do geologists tend to be skeptics? Is it because they are, as Gore and the “consensus” charge, in the pay of the oil industry? Perhaps, but there may be other, more scientific reasons. As Peter Sciaky, a retired geologist, writes:

A geologist has a much longer perspective. There are several salient points about our earth that the greenhouse theorists overlook (or are not aware of). The first of these is that the planet has never been this cool. There is abundant fossil evidence to support this — from plants of the monocot order (such as palm trees) in the rocks of Cretaceous Age in Greenland and warm water fossils in sedimentary rocks of the far north. This is hardly the first warming period in the earth’s history. The present global warming is hardly unique. It is arriving pretty much “on schedule.”

One thing, for sure, is that the environmental community has always spurned any input from geologists (many of whom are employed by the petroleum industry). No environmental conference, such as Kyoto, has ever invited a geologist, a paleontologist, a paleo-climatologist. It would seem beneficial for any scientific investigatory to include such scientific disciplines.

Among all my liberal and leftist friends (and I am certainly one of those), I know not a one who does not accept that global warming is an event caused by mankind. I do not know one geologist who believes that global warming is not taking place. I do not know a single geologist who believes that it is a man-made phenomenon.3

Finally, a retired scientist who emailed me after reading one of my climate columns in the Times Colonist observed: “Most of my geology friends are skeptics — but it has become politically incorrect to voice such views.”

Current climate conditions are not unusual

Geologists tend to question the anthropogenic theory because their education tells them that current climate conditions are not unusually warm, based on either the past few thousand years, or the past few hundred thousand years, or the past tens of millions of years, or even the past hundreds of millions of years.

Figure 1. Temperatures since 1860. Source: R.M. Carter
Temperatures since 1860. Source: R.M. Carter.

It’s possible to look at a graph of the past century and conclude: “Oh, my God, the planet is burning up!” After all, the temperature has been rising, more or less, since the 1850’s, with a dip from the 1940’s to the mid-1970’s. The chart to the right shows temperature and carbon dioxide levels from 1860 to now.4

But what if we take a longer view? That presents quite a different picture. Only 400 years ago, the planet was quite cold, a period known as the Little Ice Age (roughly 1300-1850). Before that, though, during the Medieval Warm Period (roughly 1000-1300), the planet was a degree or two Celsius warmer than today, to the point where Greenland was warm enough for settlement by the Vikings. The Medieval Warm Period and Little Ice Age were clearly a natural occurrences since industrial carbon emissions weren’t yet a factor. Figure 1 is a graph of the last thousand years based on work by climatologist H.H. Lamb.

Temperatures over the last 1,000 years: H.H. Lamb
Figure 1. Lamb graph of temperature over the past 1,000 years

Curiously, the temperature graph preferred by the Intergovernmental Panel on Climate Change, the famous “hockey stick,” smooths out the Medieval Warm Period and Little Ice Age to create an impression that twentieth-century warming is “the warmest in 1,000 years” (Figure 2). Faced with the flaws in this graph, the IPCC has since dropped it and now claims the climate is the warmest in 400 years, which isn’t that impressive given that we’re coming out of the Little Ice Age.

IPCC hockey stick graph
Figure 2. IPCC hockey stick graph of the past 1,000 years

Over the past 4,000 years, the planet has also experienced warm and cool periods, again quite naturally. In fact, warm times seem to recur on a cycle of about 1,000-1,500 years, as Figure 3 shows.5 The 20th century’s warming appeared pretty much in line with this millennial cycle.

Warming every 1,000 years
Figure 3. Warming every 1,000 years or so. Source: R.M. Carter

Going back 8,000 years or so, we encounter the Holocene Optimum, which was 2-3 degrees Celsius warmer than today’s temperatures — naturally.

Let’s expand our view once again, to the past 450,000 years (Figure 4). What do we see? A roller-coaster ride of glacials (cold times) and interglacials (warm times), on a cycle of about 100,000 years.

A glacial cycle every 100,000  years
Figure 4. A glacial cycle every 100,000 years

By the way, this is the chart, based on ice core readings taken in Antarctica, that Gore uses in his film An Inconvenient Truth. Gore doesn’t try to explain why this roller coaster has occurred, since if changes in carbon dioxide levels were causing the cycle of glaciations and interglaciations, as Gore implies, then the logical question is what caused the changes in carbon dioxide levels?

Gore doesn’t say, because to do so would destroy his case, but here’s what science says: temperature changes precede carbon dioxide level changes by several hundred years, and temperature changes are caused by changes in solar intensity called the Milankovitch Cycles, not carbon dioxide. The Milankovitch Cycles, based on the earth’s changing position in relation to the sun, appear to be the ultimate drivers of climate over the past few million years.

The four previous interglacials were warmer than today’s

Another interesting observation that Gore doesn’t make because it would destroy his case: the four previous interglacials shown on his chart are all warmer than today’s interglacial (the green line in Figure 4 shows how today’s average temperature compares with that of the three previous interglacials).

Also, note that the interglacial peaks are very steep. Before an interglacial becomes a glacial, warming occurs relatively rapidly (if the warming was slow, the curve would be more rounded), and cooling also occurs rapidly.

If our planet is near the top of its interglacial cycle, then we’d be getting — as part of a natural process — the rapid warming climatologists are so alarmed about. And, we can expect rapid cooling when the balance tips (the steep downward slope). To worry about global warming at this stage in our planet’s geological history seems silly from the geologist’s perspective.

As further evidence that we may be near the high point of the climate cycle, the planet has not warmed since 1998, even though carbon dioxide levels have increased steadily. We may well be heading into a new glaciation while spending billions of dollars on reducing carbon emissions on the false premise that the planet is getting too warm.

During the glacials, much of the northern hemisphere (and Antarctica, of course) is covered with ice two and three kilometres thick. Within our roughly two-million-year-old ice age, the glacials last about 80,000 years. The warmer interglacials, which make global civilization possible, last only 10,000-20,000 years. Our interglacial, the Holocene, began about 13,000 years ago, so we’re well past the half-way point in this cycle of warming and looking at a new glacial in the next few centuries or millennia. Warming is, therefore, from the geologist’s point of view, the least of our problems.

Temperatures have been falling for 65 million years

Suppose we take an even longer geological view: the last 65 million years. Here we see a temperature graph that looks like a double-diamond ski slope: the planet has been gradually but steadily cooling during this time (see Figure 5).6) Note how the climate has seesawed in the past two million years, and how close the tips of the warming periods are to the point where glaciations return.

Global temperatures falling
Figure 5. Global temperature falling for 70 million years

The temperature 65 million years ago, when the dinosaurs were obliterated by a comet, was about 22 degrees Celsius; today, the planet’s average temperature is about 12 degrees Celsius. Carbon dioxide levels have also been falling over this time, but much more rapidly than the temperature (which should, in all but the most die-hard “consensus” climatologists’ minds, destroy the idea that carbon dioxide drives temperature). For most of this time on our planet there were no polar ice caps and, yes, the sea levels were many metres higher than today. Humanity can deal with higher sea levels; we’ll have a lot more trouble coping with three-kilometre-high walls of glacial ice.

Finally, let’s look at the very long-range picture: earth over the past 600 million years (Figure 6). Again, we see fluctuations of temperature but, overall, the planet has been much warmer (and with much higher levels of carbon dioxide) than today, and yet life managed to evolve and flourish.

CO2 and temperature over 600 million years
Figure 6. Temperature and CO2 levels over 600 million years

The planet didn’t experience “oblivion,” as the Secretary General of the UN, Ban Ki-Moon, suggested at the Bali conference on climate change in 2007. It’s curious that not one of the thousands of so-called climate experts at that conference saw fit to educate Ki-Moon on the geological facts before (or, apparently, after) his speech.

Geologists are fully aware that our planet is not unusually warm at the moment, it is unusually cold. They also know that carbon dioxide is not the villain when it comes to warming — for most of earth’s history, temperature and carbon dioxide have shown only the most tenuous relationship, as Figure 6 shows. The correlation today of rising carbon dioxide levels and rising temperatures that worries climate scientists so much is likely just coincidence.

Overall, as Lamb observed, “Seemingly objective statistics may produce a variety of verdicts which are actually arbitrary in that they depend on the choice of observation period.”7 Alarmists like Al Gore have chosen to focus on the past century, and therefore they worry about warming. Geologists take a longer time-frame and know that the planet has been much warmer in the past without “thermageddon,” that we are in an ice age, and that the biggest future problem we face is not warming but cooling.

Who’s right, the geologists or the computer-based climate scientists? There is no certainty in science (a fact that “consensus” climate science seems to have forgotten). However, if we think like a geologist rather than a computer climate specialist, we know that today’s climate is well within past natural variability — for example, previous interglacials and even previous warm cycles within this interglacial were warmer than today.

In other words, the record of past climate history makes it very likely that today’s climate change is based on natural, cyclical factors, not human factors, and that what we need to worry about is a planet that is colder, not warmer.


  1. Gordon Jaremko, “Causes of climate change varied: poll.” Edmonton Journal, March 6, 2008.
  2. L.C. Gerhard and B.M. Hanson, “Ad hoc committee on global climate issues: Annual report.” AAPG Bulletin, vol. 84, issue 4 (April 2000), pp. 466-471. Available at
  3. Quoted in Alexander Cockburn, “Dissidents against dogma.” Counterpunch, June 9/10, 2007. Available at
  4. It’s interesting to note that the rise in temperature from about 1900 to 1940 is just as steep as the rise from the 1970’s to now, with much lower carbon dioxide levels, so presumably that rise was “natural,” but, according to Gore et al., the current, similar rise must be human-made. The chart comes from R.M. Carter’s “The Myth of Dangerous Human-Caused Climate Change.”
  5. Graph comes from R.M. Carter, “The Myth of Dangerous Human-Caused Climate Change.” For details on the millennial cycle, see S. Fred Singer and Dennis Avery, Unstoppable Global Warming: Every 1,500 Years.
  6. From Brian S. John, editor, The Winters of the World: Earth Under the Ice Ages. Newton Abbot: David & Charles, 1973, p. 183.
  7. H.H. Lamb, Climate, History, and the Modern World. New York: Methuen, 1982, p. 16.