Archive for March, 2010


What Real Scientists Do: Global Warming Science vs. Global Whining Scientists

March 30, 2010

by David Schnare
March 16, 2010

According to M. Mitchell Waldrop, editorial page editor for Nature,
“global-warming deniers . . . are sowing doubts about the fundamental [climate change] science.” Further, Waldrop argues in his op-ed “Climate of Fear, “scientists’ reputations have taken a hit.”

Let’s ignore the snarky reference to “deniers” and ask: is science and are
scientists under attack? The answer is Yes. But in an intellectual sense, isn’t
this the essence of falsifiable, non-verifiable physical science?

Climategate (et al.) is not simply about “deniers” and Waldrop’s complaint that
skeptics are “stok[ing] the angry fires of talk radio, cable news, the
blogosphere and the like.” It’s much more nuanced than that.

As a quick aside, perhaps Dr. Waldrop can be forgiven for failing to see the big
picture. To critics (can he tolerate them?), he is a deer in the headlights of
universal, Internet-quick scientific scrutiny. And there are a lot of smart
`amateurs’ mixing it up with the pros (who likes competition?). Consider the
view of his colleague-in-arms Paul Ehrlich, who profoundly stated in the same
March 10th editorial: “Everyone is scared shitless, but they don’t know what to do.”

Perhaps we can help them.

Three Key Issues

Sorting this out, there are three important issues:

(1) Is science under attack?

(2) Are scientists under attack? and

(3) Who is doing the attacking?

The third questions is by far the most interesting, but let us first dispose of
questions one and two.

Is Science Under Attack?

To question one, the answer is of course it is. That’s how science works. One of
the simplest explanations of this is often used by Martin Hertzberg, a retired
Navy meteorologist with a PhD in physical chemistry-–in other words, a real
scientist. He writes:

“The difference between a scientist and propagandist is clear. If a scientist
has a theory, he searches diligently for data that might contradict it so that
he can test it further or refine it. The propagandist carefully selects only the
data that agrees with his theory and dutifully ignores any that contradicts it.
The global warming alarmists don’t even bother with data! All they have are
half-baked computer models that are totally out of touch with reality and have already been proven to be false.”

Science is always under attack, and the best science is under attack by the very scientists who construct the hypotheses at issue. Sadly, this is not what is generally going on with climate change.

To help our climate science friends, which would include anyone who worked on the IPCC Work Group I report, here are just two hypotheses that they might wish to diligently examine:

There is no evidence of historic temperature increases or temperature levels
similar to what we have observed in the past 40 years that could arise from
natural causes.

The climate models upon which the IPCC reports rely fully incorporate the
influences of water vapor, the El Nino southern, the Pacific decadal
oscillation, the Atlantic multi-decadal oscillation, the Arctic oscillation, and
the causes of long-term (1,500, 5,000 and 20,000 year) climate variation, thus eliminating the potential to mistake a natural cause in climate variation with a man-made cause of variation.

If the IPCC scientists were able to falsify either of these, then the entire
basis for alarmism about climate change would fall apart, as these are the
“fundamental” climate science about which Dr. Waldrop is so concerned.

There is some hope, however. After being bludgeoned by criticism and demands for data from scientists outside his personal circle of climate alarmists, and apparently a scientist within his own offices who released the now infamous Climategate emails, Dr. Phil Jones, director of the Climate Research Institute at East Anglia University, and IPCC scion, has admitted the following (as summarized by Indur Goklany):

Neither the rate nor magnitude of recent warming is exceptional.

There was no significant warming from 1998-2009. According to the IPCC we should have seen a global temperature increase of at least 0.2°C per decade.

The IPCC models may have overestimated the climate sensitivity for greenhouse gases, underestimated natural variability, or both.

This also suggests that there is a systematic upward bias in the impacts estimates based on these models just from this factor alone.

The logic behind attribution of current warming to well-mixed man-made greenhouse gases is faulty.

The science is not settled, however unsettling that might be.

There is a tendency in the IPCC reports to leave out inconvenient findings, especially in the part(s) most likely to be read by policy makers.

Are Scientists Under Attack?

It is unusual that scientists fighting other scientists make newspaper
headlines. One isn’t supposed to be bludgeoned at all, and the discourse isn’t
supposed to be on the BBC webpage, but rather in the scientific literature.
Hence, the second question: Are scientists under attack?

Here nuance begins to enter. Some scientists who should be under attack are
under attack. Some who should be are not, and some who should not be are. A small number of examples make this point.

Scientists at the East Anglia University’s Climate Research Center (CRU), the
NASA Goddard Institute for Space Studies, and the Pennsylvania State University, to name but three, have refused to respond to Freedom of Information requests seeking data and the code for the computer models they have used in preparation of scientific papers. These scientists deserve to be under attack. As the Institute of Physics explained in its submission to Parliament regarding the released CRU emails:

Fundamentally, we consider it should be inappropriate for the verification of
the integrity of the scientific process to depend on appeals to Freedom of
Information legislation. Nevertheless, the right to such appeals has been shown to be necessary.

If honest science is to survive, the information underlying scientific studies
must be available to anyone seeking to validate or replicate the work. Any
scientist who stands in the way of that principle should not only be under
attack, they should be cashiered from the profession.

Now, as to those who are not under attack but should be. These are often
individuals who have reached emeritus status and are “too big to fail”, one
supposes. Let me offer but one example, Professor Steven Schneider. He served as a climate researcher for the National Center for Atmospheric Research in Boulder, Colorado for two decades and is one of the most ardent advocates of the Global Warming Theory. He joined the faculty of Stanford University in 1991 and remains there today. He has stated the following:

“It is journalistically irresponsible to present both sides [of the global
warming theory] as though it were a question of balance.” (Quoted in the Boston Globe, May 31, 1992.)

“Looking at every bump and wiggle… is a waste of time…. I don’t set very much store by looking at the direct evidence.” (Quoted in the Washington Times, June 12, 1992)

“[We] have to offer up scary scenarios, make simplified dramatic statements and make little mention of any doubts we may have. Each of us has to decide what the right balance is between being effective and being honest.” (Quoted by Dixy Lee Ray in Trashing the Planet, 1990)

Schneider is a Hertzberg propagandist. He and his fellow travelers should be the focus of intense examination as they seek to deflect debate away from the
science itself. I don’t, however, see the bastions of science, including the
National Academy, cleaning up its own messes. These supposed leaders of science have the rostrum and they are not going to give it up. They control the science purse strings, access to journals, and most of the lay press. They are the emperors without clothing.

These propagandists are not to be confused with the majority of scientists who have no political agenda and who simply want to be scientists. These are often the scientists who are under attack and should not be. Among them are Richard Lindzen, MIT, Roger Pielke, Sr., University of Colorado – Boulder, and John Christy, UAH. These people refuse to go beyond where observation takes them. They are under attack because they refuse to participate in the propaganda campaigns.

Who’s Doing the Attacking?

Now for the fascinating question, who is attacking the “settled science”? The
answer reflects an entirely new paradigm.

In the past, adversarial science most often played out in the courts. A perfect
recent example is found in the recent matter of Native Ecosystems Council v.
Tidwell. The court held that government scientists were arbitrary and capricious in their decision-making because they relied on models instead of actual observation. Specifically, the Forest Service attempted to claim that a 40,000 acre area of sagebrush was a breeding ground for the sage grouse, even though they had diligently looked for these birds and had not been able to find either one bird or one breeding site in over 15 years. Nevertheless, the government scientists claimed that their habitat model suggested that it should be a breeding ground and thus it was one and thus it demanded protection. As the court stated, that “just doesn’t cut it.”

Notably, in dissent, one judge was prepared to rely on the authority of the
government instead of the science itself. That is, of course, the crux of the
problem. It is time to get past “authority” and get to the science, and that is
the new paradigm.

Propagandists like Steve Schneider loudly argue that the “deniers” or “skeptics” should be disregarded. To him the debate should be within the scientific community. The skeptics aren’t scientists but shills for Big Oil. Even Nature editor Waldrop proclaims that “the IPCC error [regarding glaciers] was
originally caught by scientists, not skeptics”. (Brit. Spelling).

Schneider and Waldrop are wrong. There is a new breed of scientist in this fray, and they don’t take money from Big Oil (or little oil), and they publish in the peer-reviewed literature and they are not afraid of big data sets or complex computer code. I call them the “mad-as- hell, won’t-take-it-anymore” scientists.

Who are These Guys?

In the main, these are the now retired baby-boomers who have nothing better to do with their time than apply their considerable skills in attempting to replicate or falsify climate alarmism science. Steve McIntyre, working with Ross McKitrick, destroyed Michael Mann’s infamous “hockey stick”, and in the process demonstrated that data does exist to show that natural causes can result in temperatures higher than what we observed in the 1990’s.

McIntyre continues to seek the data underlying the IPCC reports. Although
McIntyre and McKitrick publish in the peer-reviewed literature, their work on the Internet at Climate Audit has been the more powerful driver for scientific openness and honest analysis. They put science on open display in a manner that allows others to replicate or critique their work. Others of this ilk are Ken Stewart, Anthony Watts, S. Fred Singer, Frederick Seitz, Chauncey Starr, and the father of the Gaia theory, James Lovelock.

Lovelock, the 90-year-old British scientist, who has worked for NASA and paved the way for the detection of man-made aerosol and refrigerant gases in the atmosphere, called for greater caution in climate research. Reflecting on the current status of climate science, Lovelock makes the pithy point that “quite often, observations done by hand are accurate but all the theoretical stuff in between tends to be very dodgy and I think they are seeing this with climate change.”


So, what would a real scientist do? Perhaps they should look backward to see
what their retired parents are doing and try to do as well. Bit embarrassing
when the old man or old woman takes the children to task for abandoning the
touch stone of science. Happily, until they are dead, it looks like the
grey-haired old biddies are going to look askance at their propaganda progeny.

David W. Schnare, Esq. Ph.D., is director of the Center for Environmental
Stewardship, Thomas Jefferson Institute for Public Policy.


When to Doubt a Scientific ‘Consensus’

March 17, 2010

This from  – Jay Richards in The American Blog (

A December 18 Washington Post poll, released on the final day of the ill-fated Copenhagen climate summit, reported “four in ten Americans now saying that they place little or no trust in what scientists have to say about the environment.” Nor is the poll an outlier. Several recent polls have found “climate change” skepticism rising faster than sea levels on Planet Algore (not to be confused with Planet Earth, where sea levels remain relatively stable).

Many of the doubt-inducing climate scientists and their media acolytes attribute this rising skepticism to the stupidity of Americans, philistines unable to appreciate that there is “a scientific consensus on climate change.” One of the benefits of the recent Climategate scandal, which revealed leading climate scientists manipulating data, methods, and peer review to exaggerate the evidence of significant global warming, may be to permanently deflate the rhetorical value of the phrase “scientific consensus.”

Even without the scandal, the very idea of scientific consensus should give us pause. “Consensus,” according to Merriam-Webster, means both “general agreement” and “group solidarity in sentiment and belief.” That pretty much sums up the dilemma. We want to know whether a scientific consensus is based on solid evidence and sound reasoning, or social pressure and groupthink.

Anyone who has studied the history of science knows that scientists are not immune to the non-rational dynamics of the herd. Many false ideas enjoyed consensus opinion at one time. Indeed, the “power of the paradigm” often shapes the thinking of scientists so strongly that they become unable to accurately summarize, let alone evaluate, radical alternatives. Question the paradigm, and some respond with dogmatic fanaticism.

We shouldn’t, of course, forget the other side of the coin. There are always cranks and conspiracy theorists. No matter how well founded a scientific consensus, there’s someone somewhere—easily accessible online—that thinks it’s all hokum. Sometimes these folks turn out to be right. But often, they’re just cranks whose counsel is best disregarded.

So what’s a non-scientist citizen, without the time to study the scientific details, to do? How is the ordinary citizen to distinguish, as Andrew Coyne puts it, “between genuine authority and mere received wisdom? Conversely, how do we tell crankish imperviousness to evidence from legitimate skepticism?” Are we obligated to trust whatever we’re told is based on a scientific consensus unless we can study the science ourselves? When can you doubt a consensus? When should you doubt it?

Your best bet is to look at the process that produced, maintains, and communicates the ostensible consensus. I don’t know of any exhaustive list of signs of suspicion, but, using climate change as a test study, I propose this checklist as a rough-and-ready list of signs for when to consider doubting a scientific “consensus,” whatever the subject. One of these signs may be enough to give pause. If they start to pile up, then it’s wise to be suspicious.

(1) When different claims get bundled together.

Usually, in scientific disputes, there is more than one claim at issue. With global warming, there’s the claim that our planet, on average, is getting warmer. There’s also the claim that human emissions are the main cause of it, that it’s going to be catastrophic, and that we have to transform civilization to deal with it. These are all different assertions with different bases of evidence. Evidence for warming, for instance, isn’t evidence for the cause of that warming. All the polar bears could drown, the glaciers melt, the sea levels rise 20 feet, Newfoundland become a popular place to tan, and that wouldn’t tell us a thing about what caused the warming. This is a matter of logic, not scientific evidence. The effect is not the same as the cause.

There’s a lot more agreement about (1) a modest warming trend since about 1850 than there is about (2) the cause of that trend. There’s even less agreement about (3) the dangers of that trend, or of (4) what to do about it. But these four propositions are frequently bundled together, so that if you doubt one, you’re labeled a climate change “skeptic” or “denier.” That’s just plain intellectually dishonest. When well-established claims are fused with separate, more controversial claims, and the entire conglomeration is covered with the label “consensus,” you have reason for doubt.

(2) When ad hominem attacks against dissenters predominate.

Personal attacks are common in any dispute simply because we’re human. It’s easier to insult than to the follow the thread of an argument. And just because someone makes an ad hominem argument, it doesn’t mean that their conclusion is wrong. But when the personal attacks are the first out of the gate, and when they seem to be growing in intensity and frequency, don your skeptic’s cap and look more closely at the evidence.

When it comes to climate change, ad hominems are all but ubiquitous. They are even smuggled into the way the debate is described. The common label “denier” is one example. Without actually making the argument, this label is supposed to call to mind the assertion of the “great climate scientist” Ellen Goodman: “I would like to say we’re at a point where global warming is impossible to deny. Let’s just say that global warming deniers are now on a par with Holocaust deniers.”

There’s an old legal proverb: If you have the facts on your side, argue the facts. If you have the law on your side, argue the law. If you have neither, attack the witness. When proponents of a scientific consensus lead with an attack on the witness, rather than on the arguments and evidence, be suspicious.

(3) When scientists are pressured to toe the party line.

The famous Lysenko affair in the former Soviet Union is often cited as an example of politics trumping good science. It’s a good example, but it’s often used to imply that such a thing could only happen in a totalitarian culture, that is, when all-powerful elites can control the flow of information. But this misses the almost equally powerful conspiracy of agreement, in which interlocking assumptions and interests combine to give the appearance of objectivity where none exists. For propaganda purposes, this voluntary conspiracy is even more powerful than a literal conspiracy by a dictatorial power, precisely because it looks like people have come to their position by a fair and independent evaluation of the evidence.

Tenure, job promotions, government grants, media accolades, social respectability, Wikipedia entries, and vanity can do what gulags do, only more subtly. Alexis de Tocqueville warned of the power of the majority in American society to erect “formidable barriers around the liberty of opinion; within these barriers an author may write what he pleases, but woe to him if he goes beyond them.” He could have been writing about climate science.

Climategate, and the dishonorable response to its revelations by some official scientific bodies, show that scientists are under pressure to toe the orthodox party line on climate change, and receive many benefits for doing so. That’s another reason for suspicion.

(4) When publishing and peer review in the discipline is cliquish.

Though it has its limits, the peer-review process is meant to provide checks and balances, to weed out bad and misleading work, and to bring some measure of objectivity to scientific research. At its best, it can do that. But when the same few people review and approve each other’s work, you invariably get conflicts of interest. This weakens the case for the supposed consensus, and becomes, instead, another reason to be suspicious. Nerds who follow the climate debate blogosphere have known for years about the cliquish nature of publishing and peer review in climate science (see here, for example).

(5) When dissenting opinions are excluded from the relevant peer-reviewed literature not because of weak evidence or bad arguments but as part of a strategy to marginalize dissent.

Besides mere cliquishness, the “peer review” process in climate science has, in some cases, been consciously, deliberately subverted to prevent dissenting views from being published. Again, denizens of the climate blogosphere have known about these problems for years, but Climategate revealed some of the gory details for the broader public. And again, this gives the lay public a reason to doubt the consensus.

(6) When the actual peer-reviewed literature is misrepresented.

Because of the rhetorical force of the idea of peer review, there’s the temptation to misrepresent it. We’ve been told for years that the peer-reviewed literature is virtually unanimous in its support for human-induced climate change. In Science, Naomi Oreskes even produced a “study” of the relevant literature supposedly showing “The Scientific Consensus on Climate Change.” In fact, there are plenty of dissenting papers in the literature, and this despite mounting evidence that the peer-review deck was stacked against them. The Climategate scandal also underscored this: The climate scientists at the center of the controversy complained in their emails about dissenting papers that managed to survive the peer-review booby traps they helped maintain, and fantasized about torpedoing a respected climate science journal with the temerity to publish a dissenting article.

(7) When consensus is declared hurriedly or before it even exists.

A well-rooted scientific consensus, like a mature oak, usually needs time to emerge. Scientists around the world have to do research, publish articles, read about other research, repeat experiments (where possible), have open debates, make their data and methods available, evaluate arguments, look at the trends, and so forth, before they eventually come to agreement. When scientists rush to declare a consensus, particularly when they claim a consensus that has yet to form, this should give any reasonable person pause.

In 1992, former Vice President Al Gore reassured his listeners, “Only an insignificant fraction of scientists deny the global warming crisis. The time for debate is over. The science is settled.” In the real 1992, however, Gallup “reported that 53% of scientists actively involved in global climate research did not believe global warming had occurred; 30% weren’t sure; and only 17% believed global warming had begun. Even a Greenpeace poll showed 47% of climatologists didn’t think a runaway greenhouse effect was imminent; only 36% thought it possible and a mere 13% thought it probable.” Seventeen years later, in 2009, Gore apparently determined that he needed to revise his own revisionist history, asserting that the scientific debate over human-induced climate change had raged until as late as 1999, but now there was true consensus. Of course, 2009 is when Climategate broke, reminding us that what had smelled funny before might indeed be a little rotten.

(8) When the subject matter seems, by its nature, to resist consensus.

It makes sense that chemists over time may come to unanimous conclusions about the results of some chemical reaction, since they can replicate the results over and over in their own labs. They can see the connection between the conditions and its effects. It’s easily testable. But many of the things under consideration in climate science are not like that. The evidence is scattered and hard to keep track of; it’s often indirect, imbedded in history and requiring all sorts of assumptions. You can’t rerun past climate to test it, as you can with chemistry experiments. And the headline-grabbing conclusions of climate scientists are based on complex computer models that climate scientists themselves concede do not accurately model the underlying reality, and receive their input, not from the data, but from the scientists interpreting the data. This isn’t the sort of scientific endeavor on which a wide, well-established consensus is easily rendered. In fact, if there really were a consensus on all the various claims surrounding climate science, that would be really suspicious. A fortiori, the claim of consensus is a bit suspicious as well.

(9) When “scientists say” or “science says” is a common locution.

In Newsweek’s April 28, 1975, issue, science editor Peter Gwynne claimed that “scientists are almost unanimous” that global cooling was underway. Now we are told, “Scientists say global warming will lead to the extinction of plant and animal species, the flooding of coastal areas from rising seas, more extreme weather, more drought and diseases spreading more widely.” “Scientists say” is hopelessly ambiguous. Your mind should immediately wonder: “Which ones?”

Other times this vague company of scientists becomes “SCIENCE,” as when we’re told “what science says is required to avoid catastrophic climate change.” “Science says” is an inherently weasely claim. “Science,” after all, is an abstract noun. It can’t say anything. Whenever you see that locution used to imply a consensus, it should trigger your baloney detector.

(10) When it is being used to justify dramatic political or economic policies.

Imagine hundreds of world leaders and nongovernmental organizations, science groups, and United Nations functionaries gathered for a meeting heralded as the most important conference since World War II, in which “the future of the world is being decided.” These officials seem to agree that institutions of “global governance” need to be established to reorder the world economy and massively restrict energy resources. Large numbers of them applaud wildly when socialist dictators denounce capitalism. Strange philosophical and metaphysical activism surrounds the gathering. And we are told by our president that all of this is based, not on fiction, but on science—that is, a scientific consensus that human activities, particularly greenhouse gas emissions, are leading to catastrophic climate change.

We don’t have to imagine that scenario, of course. It happened in Copenhagen, in December. Now, none of this disproves the hypothesis of catastrophic, human induced climate change. But it does describe an atmosphere that would be highly conducive to misrepresentation. And at the very least, when policy consequences, which claim to be based on science, are so profound, the evidence ought to be rock solid. “Extraordinary claims,” the late Carl Sagan often said, “require extraordinary evidence.” When the megaphones of consensus insist that there’s no time, that we have to move, MOVE, MOVE!, you have a right to be suspicious.

(11) When the “consensus” is maintained by an army of water-carrying journalists who defend it with uncritical and partisan zeal, and seem intent on helping certain scientists with their messaging rather than reporting on the field as objectively as possible.

Do I really need to elaborate on this point?

(12) When we keep being told that there’s a scientific consensus.

A scientific consensus should be based on scientific evidence. But a consensus is not itself the evidence. And with really well-established scientific theories, you never hear about consensus. No one talks about the consensus that the planets orbit the sun, that the hydrogen molecule is lighter than the oxygen molecule, that salt is sodium chloride, that light travels about 186,000 miles per second in a vacuum, that bacteria sometimes cause illness, or that blood carries oxygen to our organs. The very fact that we hear so much about a consensus on catastrophic, human-induced climate change is perhaps enough by itself to justify suspicion.

To adapt that old legal aphorism, when you’ve got decisive scientific evidence on your side, you argue the evidence. When you’ve got great arguments, you make the arguments. When you don’t have decisive evidence or great arguments, you claim consensus.


Yukon rocks point to ancient ‘snowball Earth’

March 4, 2010

Last Updated: Thursday, March 4, 2010 | 2:31 PM ET

CBC News
In this Yukon mountain, a maroon-coloured, iron-rich layer of glacial deposits 716.5 million years old can be seen on top of older, grey carbonate reef.In this Yukon mountain, a maroon-coloured, iron-rich layer of glacial deposits 716.5 million years old can be seen on top of older, grey carbonate reef. (Francis A. Macdonald/Harvard University)Geologists working in the Canadian North have found evidence that the Earth’s oceans were covered in ice all the way to the tropics more than 700 million years ago.

The researchers’ findings give strength to the “snowball Earth” idea, that the planet was virtually covered in ice around the same time the first animals evolved.

The American and Canadian geologists analyzed rocks from the Yukon and Northwest Territories and found glacial deposits 716.5 million years old, based on precision uranium dating techniques.

The purplish glacial deposits were found on top of old reef material composed of carbonate, shifted north by the movement of tectonic plates.

The magnetic and chemical composition of the rocks indicate that they were located at sea level in the tropics — about 10 degrees latitude — when the deposits took place.

The study published this week in Science is the first evidence, the geologists say, that this glacier, called the Sturtian glaciation, reached the tropical latitudes.

Francis Macdonald of Harvard University, the study’s lead author, said that the research provides “direct evidence that this particular glaciation was a ‘snowball Earth’ event.”

“Our data also suggests that the Sturtian glaciation lasted a minimum of five million years,” said Macdonald, in a statement.

Other evidence, from fossils and mineral isotopes, suggests the Sturtian glaciation could have lasted as long as 20 million years, from 720 million to 700 million years ago.

Geologists don’t know what caused the Earth to freeze over or what ended the glacier event.

Fossils also show that early complex life forms, called eukaryotes, emerged before the Earth froze over and somehow survived the glaciation.

“The fossil record suggests that all of the major eukaryotic groups, with the possible exception of animals, existed before the Sturtian glaciation,” Macdonald said.

“The questions that arise from this are: If a snowball Earth existed, how did these eukaryotes survive? Moreover, did the Sturtian snowball Earth stimulate evolution and the origin of animals?” he said.

MacDonald said that even a snowball Earth would have warm spots of open water that would allow sunlight through, allowing life to survive. The deep freeze could have even spurred the evolution of animals from more primitive eukaryotic life.

“From an evolutionary perspective, it’s not always a bad thing for life on Earth to face severe stress,” he said.

Good work by our friends to the north.  BTW – the “snowball earth” concept is not new.  Geologist have been discussing it for at least 15 years.  If you are interested check out this poster:

Macdonald, F., Halverson, G., Roots, C., Schmitz, M., and Crowley, J., 2009. Calibrating and Correlating Neoproterozoic Strata in the Yukon. [2.9 MB ]  on


Proxies, proxies, proxies

March 2, 2010

Anyone viewing any of the discussion regarding past temperature reconstructions have come across the use of a “proxy” as a stand-in for a temperature measurement.  A proxy is some form of determination or measurement that is shown to be dependent on another factor in which you are interested.  In this case, the proxies are used as a stand-in to help make a determination of the relative measurement of past temperatures.   Why do we need proxies to determine temperatures in the past?  Because direct measurement of temperature has only been available since the invention of the thermometer with a standardized temperature scale which happened in the early 1700’s.   Before the 1700’s there had been some attempts to construct some form of a thermometer, but no standardized temperature scale was adopted and the resulting information non-comparable between instruments.   The new standardized scale (Fahrenheit) thermometer was a true state-of-the-art scientific instrument of its time,  expensive and only found in the possession of early scientists  and the wealthy (often the same), and not in widespread distribution or use.  The further from “civilized” areas one went, the less likely that any thermometers were in use.  As a result, early temperature measurements are concentrated primarily in England, parts of Europe, and in the major population centers in eastern America.  Early temperature measurements in other areas of the world are rare or nonexistent.   What you end up with is a limited aerial extent and quality of early thermometer measurements which only goes back slightly over 300 years with emphasis in the Northern Hemisphere.  Worldwide coverage is a relatively recent occurrence, dating from the very late 1890’s and the early 20th century.    Is 300 years a good enough time frame to look at possible world-wide climate changes?  No!  We need to know much more regarding world temperatures predating the 1700’s and some way to fill in the gaps in the temperature measurements in areas of the world that have no early records.  Here is where the use of temperature proxies become very useful.

So what types of proxies are used?   We need to select a proxy where the sensitivity to temperature is not swamped by other unrelated factors.  We need a proxy that has a long-term presence (at least in the rage of up to several thousand, and perhaps greater years) and that is not far removed from the true temperature it will be measuring.  There are several usable proxies  from tree rings on long-lived trees, glacial ice from the polar parts of the world, and sediments in the deep ocean that meet some or most of these selection criteria.  Unfortunately all of these proxies have compromising factors that make the certainty of the proxy measurements ability to deliver an unbiased temperature measurement a problem.

Tree Rings

As most of us learned in elementary school botany class, trees grow by increasing the mass of the tree trunks and limbs by adding woody plant material in the form of a yearly growth rings.  These rings make-up a year-by-year record that reflects the climate conditions in which the tree grew.  A good year with adequate moisture would result in a larger growth ring than a drought year that results in little new growth and a smaller growth ring.   Visual comparisons between rings are used to estimate these differences and a determination made concerning the overall temperature at the time of growth based on the “optimum” temperature  needed for the tree growth.  Dendrochronology (especially if used with C14 dating) is a great tool for determining a date for a log used in a prehistoric hut, but other environmental factors can result in quite a bit of variability in the absolute temperature measurement determination based on a tree ring growth. Drought or very wet conditions, or difference in soils from location to location, or insect infestations, fungal infections, forest fire damage, to name just a few examples of non-temperature related effects, will limit the accuracy of tree ring temperature determinations.    Another limiting factor is that any long-term tree ring temperature record needs long-lived (300 yrs old or greater age) species of trees.  Unfortunately most tree species are not very long lived (or harvested for lumber, etc. in the recent past) and those tree that do meet our requirements are not widely dispersed.  This severely limits the usability of tree rings for historical temperature reconstructions.  Another problem with tree rings as a temperature proxy is that most tropical trees lack well defined growth rings (when everyday of the year is a good growth day,  ring definition is generally non-existent) giving us a real data “gap” over large portions of the globe.    Scientist working with these types of proxy data use a variety of statistical methods to help to “normalize” all these type of temperature determinations and the level of “statistical certainty” varies dramatically from area to area.  Tree rings analysis must be allied with other types of measurements as a check and remain a scientific iffy piece of data when used by itself as unassailable proof of the temperature determination.  As proxies go, tree ring analyses have the most overall error on temperature determinations.   The following graph show one of these temperature reconstructions (note the temp scale is expanded to emphasize the relative temperature changes).

Deep Ocean Sediments

Like tree rings, sediments deposited on the deep ocean floors also show a form of seasonality.  Warm seasons are related to high marine production; cold seasons – lower productivity.

Core photo from IODP/USIO

There is a long history of deep ocean drilling as a vehicle for geological, biological, and oceanographic study starting with the Deep Sea Drilling Project (1963 through 1983), continuing through the Ocean Drilling Program (1985 through 2004) which has evolved into the present Integrated Ocean Drilling Program.  Initially the DSDP and ODP focus was on basic earth and biological sciences research but has evolved over time (as the IODP) into one of the main collectors of proxy data on temperatures for climate reconstructions.  There are a whole variety of sophisticated isotopic analyses  conducted in these sediment samples although one analysis in particular is very useful as a proxy for past temperature.  The ratio of the stable isotopes 18O to 16O  of oxygen is particularly useful.  The heaver isotope 18O condenses more readily a temperature decreases and falls as precipitation, while the lighter isotope 16O becomes more concentrated.  Sediment (actually shells of a family microorganisms called foraminifera [aka diatoms])  enriched in 16O shows temperature cooling and sediment enriched in 18O shows temperature warming.


Coupled with 14C dating of organic material in the sediments allows for detailed temperature reconstructions over time ( to around 60,000 years before present) . Other isotope determinations have been used to extend the climate record to greater time intervals (back to the Cambrian (540 million years before present).  Note how the following chart shows that overall climate is much cooler starting in the Paleogene (50 MYBP) to present when compared to most of the proceeding 500 mys, and as you can see the time scale, although lengthy, does not have the same level of resolution seen with tree ring data.

Here is a reconstruction of the past 5 million years from ocean sediments.

Ice Cores

Like both tree rings and deep ocean sediments, glacial ice from both the arctic and antartic can also show layers seasonal layers created by the accumulation of yearly snowfall.  As each successive years’ accumulation is buried by the following year the accumulated snow it caries with it the compounds in the air and dust.   As the snow gets deeper buried by successive seasons (air temperature always below freezing), the snow crystals form firn, a granular icy material like sugar. With an accumulation of around 250 feet of thickness, the firn snow recrystallizes into ice trapping air bubbles from that time.  There can be a time lag between the age of the ice and the entrapped air which may be on the order of several decades or more.  Coring of this ice, results in an cylindrical ice plug (the core) with date of the ice increasing with the depth of the coring.   The core is recovered and kept frozen (among other practices to eliminate unwanted “modern” contamination) , and eventually stored in a facility where scientific tests are conducted.  Because there are very few areas of the work that have the geologically persistent icefields where ice cores can be collected, the important ice core temperature record are limited to parts of the Arctic and Antarctic.  Some less important cores have been collected from mountain glaciers or mountain top snowfields outside the polar regions that have provided useful although age limited information.  The two main analyses from ice cores that are directly related to climate and temperature studies involve the oxygen stable isotopes  (18O/16O) and analysis of the air composition (CO2 and others such as methane).  The two longest history ice cores are the Vostok (Antarctic) reaching back 420,000 years and the Greenland Ice Core Project/Greenland Ice Sheet Project (GRIP/GISP) core reaching back 100,000 to 123,000 years.  The two following figures are time – temperature charts for these two ice cores.