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3 of My Favorite Talks on Climate Science

There has been a lot of noise about the Paris Climate Agreement and what it means for the future. I’m not going to comment on the policy, but I would like to focus on the science. Folks on all sides of the political spectrum feel compelled to opine on what the science says. Many are unable to back their assertions up with actual literacy. Some people are genuinely curious about the subject, and a lot of folks just don’t know where to look for good scientific sources.

Unfortunately, good science sources are not always easy to come by. Most mainstream media outlets have pretty bad records on science reporting – not just climate, but any topic. Political media and tabloids are obviously worse.

I wanted to share a few videos that:

1) Are delivered by people with genuine subject expertise.
2) Represent the mainstream of the science.
3) Don’t shy away from the uncertainties and complexity of the subject matter.
4) Are really frigging interesting.

It’s a lot of material, but well worth your time.

1. Kerry Emanuel (atmospheric physicist at MIT): “What We Know About Climate Change”

If you watch no other video on the subject. This is the place to start. I think Kerry Emanuel’s talk is the best bird’s eye view of the subject.


2. Richard Alley (Paleoclimatologist, Penn): 4.6 Billion Years of Earth’s Climate History

One common trope about the earth’s climate is that “the climate has always been changing”.  True though it is, this is not a scientific sentiment. Science is more than just the observation of things that happen. Science seeks to understand those things. A big part of the scientific understanding of man-made climate change is informed by a growing body of knowledge explaining what caused major climatic shifts in times past. This is the best overview on the subject.

3. Stephen Schneider (Climate Physicist, Stanford)
Global Warming: Is the Science Settled Enough for Policy

Stephen Schneider was one of climatology’s great philosopher statesmen. Much of his work focused on the intersection of science and risk management. This talk is the best on the subject of uncertainty and risk.


Anomalies and Falsification in Science

Bluestone_the_Great_unmaskedIn science, an anomaly refers a new observation or experimental result that seems to fly in the face of conventional, well established scientific wisdom.

Anomalies are an important part of the scientific discovery process. Sometimes a particular anomaly or the collection of anomalies can precipitate a revolution in scientific thinking – dethroning an old way of thinking and bringing in a new one. A canonical example of this is the Michaelson Morley Experiment, which started the ball rolling towards the Theory of Relativity.

Anomalies are important, but they are also frequently misunderstood and frequently misused.

Peddlers of pseudo-science love anomalies. Anomalies are the raison d’etre of crank scientists the world around. It gives them a justification for their “new paradigm”. When asked what the scientific basis is for their claims they answer “because anomalies”. And there is an easy bait and switch going on:

“These anomalies falsify the scientific orthodoxy! So you might as well buy my theory instead, <wink> <wink>.”

The whole thing boils down to a confusion about falsifiability in science. Falsifiability is one of the key hallmarks of science. Philosopher Karl Popper defined science by the very idea that it makes claims that are testable and can therefore be proven wrong (falsified) by contradicting observations. Science, in the Popplerian sense, is always tentative. But, Richard Feynman says it better than I can:

(His whole segment on the scientific method can be found here. it’s great.)

Scientists take falsifiability very seriously. We take anomalies very seriously. But, the relationship between the two is where some people get confused. A good number of people are under the impression that theories are falsified with a dramatic moment of unmasking, as in “Scooby Doo, et al” (pictured above). But, science rarely happens this way. It is not so simple.

What we often refer to as a theory in science is not a singular thing. A theory is a collection of many ideas and explanations that systematically explain observations. Perhaps any one observation may be falsified, but it’s hard to falsify an entire theory in one fell swoop. In fact, if we were to throw away conventional scientific wisdom at the first sight of any anomalies, science would fundamentally lack stability.

A good scientist has the discipline to abandon an idea when it’s wrong. But, equally important is the discipline not to immediately give up on an otherwise good theory. A well-established or mature scientific framework is built on decades of observations, empirically established first-principles, and countless successful predictions. To dismiss mature science on the basis of a few anomalies would be premature, and in many cases wrong headed.

Scientists are constantly looking for new ways to push the envelope. We like anomalies because they’re way more interesting than confirming what we already know. We seek them out. We develop new instrumentation to give ourselves new sensitivity. We design new experiments to look in places we never looked before. And, the thing about venturing to new places is: you end up with a lot of false starts – mistakes, misunderstandings, experimental artifacts.

Anomalies are thus inevitable. So the right attitude is “trust but verify”, bearing in mind that verification takes time and work.

Sometimes anomalies completely dethrone the current paradigm. Far more often….they. just. don’t.

Here are some of the common fates of anomalies, from most likely to least:

1) It turns out to be an experimental artifact, a mistake. In my own field, the observation of neutrinos traveling faster than light turned out to be a consequence of a loose cable.

2) It is a real effect, but incomplete. A missing piece of the the observation, once found, restores consistency with the theory. Feynman gives a good example of this – superconductivity. At first, the discovery of superconductivity seemed to completely contradict the known understanding of atomic physics. Eventually it was realized that a very subtle quantum mechanical phenomena explained the effect. Once this is taken into account, atomic theory is again fully consistent.

3) It represents a real problem with the theory, but the essence of the theory survives with some modification (ranging anywhere from minor to major).

4) By itself or in combination with other anomalies, it dethrones the prevailing wisdom

If you’re a person who rejects broadly accepted science, you’re inclined to see any anomaly as your own Scooby Doo ending! It’s the moment you’ve been waiting for, when orthodoxy collapses and you are vindicated! It is also too easy to use these anomalies to draw inexperienced skeptics away from established science and into the rabbit hole of quack science. Which brings me to one last essential point:

Old theories are almost never dethroned by anomalies, UNTIL there is a superior alternative that explains both the old observations and the new anomalies. The really frustrating part of the pseudo-scientific bait-and-switch is the innuendo:

“Well if the mainstream science is wrong, then anyone’s guess is as good as anyone else’s. So, you might as well choose mine”

This is simply not true. In the face of deep rooted anomalies, one would be naive to blindly hold on to the established model. On the other hand, it is naive and unskeptical to settle for the first new theory to pass your way. The old paradigm survived a serious shaking and any new theory should do the same…and then some. Only hindsight is 20×20, and few people in history can claim to have successfully “picked winners” early in a scientific crisis.

So when people without any scientific credentials drive up in tinted vans, offering you the sweet indulgence of “anomalies”, just say NO and run to someone you trust :).

But seriously: I may sound like a defender of the orthodoxy. My colleagues and I take anomalies very seriously. They are the constant talk of the lunch table. The faster-than-light neutrino measurement, ridiculous as it seemed, prompted a serious and genuine discussion of theories that could violate relativity. A lot of work went in to understanding the measurement. The measurement was redone by two other experiments and neutrinos went back to being slower-than-light. And, in it’s own Scooby Doo style ending, the culprit turned out to be a loose wire.

An important, if not THE important, value of science is the willingness to revise or replace wrong ideas. But, as with anything, this is not a carte blanch principle. When anomalies appear, we should welcome them but we must also exercise care and patience.

Four of my favorite contemporary science communicators


After a long hiatus, I’m attempting a return to my blog. One thing I would like to do in this and future writings, is to share some favorite science communicators. Here are four of them: Ken Miller, Eugenie Scott, Stephen Schneider, and Kerry Emmanuel.

All four of these speakers address topics in science that carry political baggage (not so much among scientists, but in the public): evolution and climate change. These subjects are interesting because they present some of the greatest challenges to science communication. These speakers are excellent for the very reason that they are so effective at meeting the challenges: rising above ideological mirk, and getting at the heart of the science. I hope you enjoy.

Ken Miller:

Biologists -especially those who defend evolution in the classroom- are often the subject of straw man attacks, accused of everything from communism to fanatical atheism. Ken Miller is a great counter example. Miller has been an outspoken advocate for the teaching of evolutionary biology, and thus a formidable opponent of Intelligent Design/Creationism in school curricula. But, contrary to the stereotype of the “atheist scientist”, Miller is a devout and outspoken Catholic who talks openly and frankly about issues of science and religion. His Templeton essay on science and religion is among the most eloquent pieces I’ve read on the subject.

A key theme of my blog is the importance of scientific thinking and the values of science. It is not literacy of any one particular subject of science, but literacy on scientific thinking itself that is most missing from public discourse. And, the values of science are frequently under assault. At the heart of the assaults on science, is a fundamental confusion about what science is and how it works. As a religious scientist myself, I take common cause with Miller in saying that “Intelligent Design” is fundamentally unscientific and in fact anti-scientific, because it blurs and confuses distinctions between science and belief. Miller is one of the most articulate and credible speakers on the subject. I highly encourage checking out his webpage. Here is one of my favorite excerpt from a talk he gave about the Dover PA textbook trial. I’ve edited the segment for brevity, but the whole talk can be found here. Here’s the teaser:

Eugenie Scott:

In understanding the distinction between science and religion, another excellent speaker is Eugenie Scott, the recently retired director of the National Institute for Science Education (NCSE). Unlike Miller, Scott considers herself to be a strong agnostic, if not atheist. Nonetheless, she draws a sharp distinction between the value-neutrality of science and the incorrect notion that science is anti-religious. A big pet peeve of mine is when people accuse science of being dogmatically “materialist” – subscribing to a philosophy that the material world is “all there is”. In this clip, Scott hits it out of the ball park. Science does not assume a purely materialistic world; it simply restricts itself to answering materialistic questions – this is a very important distinction.

Stephen Schneider:

As this century continues to unfold, our success and survival will increasingly depend on our ability to discuss complex and sometimes yet-to-be-fully-resolved science topics. To me nothing underscores this challenge like the subject of climate change, which requires us to balance abstract long-term thinking against tangible short term problems; which still has many open questions; and which has become politicized to the point of being toxic. The issue requires a level of scientific savvy that I fear is missing from our political leadership and much of the general public at large, and it needs to change, fast. I worry very deeply about the implications of a warming planet, but I worry more about what our failure to reasonably discuss this problem says about our ability to deal with future problems of the same magnitude – and there will be more problems of this magnitude in the near future.

Unlike, my own field of pure physics, the study of climate falls under the umbrella of “complex systems science” – the study of systems that are not amenable to reductionism, where many moving parts interact on different scales and across different fields of science.

Among the figures to speak on the topic of climate science, one of my favorites is the late Stephen Schneider. Schneider was as much a philosopher of science as he is a key figure in the development of modern climatology. He spoke frequently about our “ability to survive complexity”, and cut through the difficulty of the scientific and political problems of climate change with razor precision. He gave a great series of lectures on “Climate Change: Is the Science Settled Enough For Policy?“. The whole lecture is very much worth watching. Here is a clip where he reminds us that any subject in a science is not an all-or-nothing proposition. Scientific theories have many different components, with different levels of certitude and knowledge. A critical first step to understanding science is being able to sort it into it’s various components and reason out each topic on its own merits:

Another key skill in managing the intersection of science and politics is the ability to separate between the two. Especially when the science is inherently uncertain, policy boils down to risk evaluation which is in the realm of value judgements. Science gives us probabilities and confidences, but it’s up to us to determine what to do about them. And, we have to be extremely careful not to confuse value judgments with scientific judgements. Here, Schneider lays this out:

Kerry Emanuel:

This last speaker is another climatologist, and he covers many of the same themes as Schneider. I highly recommend Emanuel’s rebuttal to a controversial article by political scientist Roger Pielke Jr on natural disasters and climate change. His article is both terse and profound, and can be found here.

One of the key problems of climate change is that politicians and the public see it as a debate between two opposite scenarios: doomsday and nothing-to-worry-about. These are what Schneider calls “the two least likely outcomes”, and they present a false choice.  The best available science lays out a continuum, a spectrum of possibilities, ranging from mostly benign to really bad. We don’t need to “choose which outcome is right”. We need to look at the spectrum and make policy decisions according to our best estimates of their likelihoods. The following is a clip from Emmanuel’s excellent summary talk, “What we know about climate change”. The whole lecture provides one of the best overviews on the topic. Here is Emmanuel laying out the basic idea and talking about the concept of tail risks:


A common tactic from dogmatic people who attack scientific theories is to accuse scientists themselves of dogma. No doubt, all scientists have our biases, and some can be quite dogmatic. But, the scientific community is largely populated by people who are turned off by ideology and prefer the complexity and nuances of the world as it is, to naive simplicity of the world as we want it it to be. At our best, we leverage our skeptical community and our methodology to place a strong check on bias and dogma. I picked these examples because they run counter to the accusations of “atheism”, “alarmism”, or “socialism” that get so cheaply tossed around by partisan hacks. These are people who embody the voice of reason, who value being reasonable and being accurate above all else, and I hope that shines through. How we think about the world has very real implications for how we ultimately act in it. It is here where science has many important things to say about the future of our society.

“The 97 Percent”

I am not a fan of the term “denier” or “denial” when tossed around on the subject of climate change. In most cases it does not serve a constructive purpose. However, in describing a recent op-ed in the WSJ by Joe Bast and Prof Roy Spencer, it is difficult for me not to use the word.

Anyone who has first-hand with the field knows that the number of published, active researchers in the field who challenge the main findings on climate change1 is miniscule. It simply can’t be more than a few percent. And one is hard pressed to find a single professional scientific organization that doesn’t make a clear statement on the subject.

Even guys like Roy Spencer, when pushed hard enough, will admit that they are a minority voice. This is why I find articles like the WSJ piece completely baffling.  In the op-ed, Spencer and Bast challenge the claim that 97% of the climate scientists agree on the main points of global warming. But here’s their bait-and-switch: they don’t really offer an alternative number and they avoid saying exactly how wrong they think that figure is, leaving much to innuendo.

First a little history

The claim that “97% of all climate scientists agree…” comes from a series of studies: Naomi Oreskes performed a literature search, looking at abstracts from 928 papers matching the keywords “climate change”. Orskes found no papers contradicting the consensus findings, as described by the International Panel on Climate Change (IPCC). Doran & Zimmerman (2009) polled 10,000 earth scientists and found a broad consensus among all scientists, with 97% agreement among those actively publishing climate research.  Anderegg et al. (2010) reviewed publicly signed declarations supporting or rejecting human-caused global warming, and again found high consensus among climate experts.  Cook et al. (2013) performed a literature search, in a similar vein to Oreskes, and found that among papers addressing the question of anthropogenic climate change 97% affirmed the consensus position. Two other surveys of note find high levels of agreement (>85%), especially among experts, though not the 97% number: A survey by the American Meteorological Society (AMS) and one by Brey and Von Storch. We will discuss these shortly.

None of these surveys is perfect. All of them have certain strengths and weaknesses, but they are useful at illustrating to the public what those in the scientific community know: that people who outright deny a warming trend, who challenge the notion of an anthropogenic cause, and who consider the effects of the warming to be harmless represent a marginal view among the broad community of experts.

Picking Nits

Surveys and literature searches are inherently imperfect, so it’s easy to raise methodological objections. This is fine. Climate change is a complex subject and not easily reduced to a yes or no question. On this basis, I am inclined to agree that one should take the exact figure 97% with a grain of salt. But, questioning whether the number is 90% or 99% is not the same as doubting that there ultimately is broad agreement. And, this is where I find the op-ed to be deceptive and obfuscating. Not only do Spencer and Bast fail  to imply a lack of consensus on harmful, man made global warming, but most of their own sources contradict them. So what have they got?

Seriously, “the Oregon Petition”?

The thing that I find most shocking about the WSJ op-ed is the retreading of the infamous “Global Warming Petition Project” (aka the Oregon Petition). It’s bizarre that Spencer and Bast spend half of their article nitpicking the methodologies of surveys based on standard practices, and then they turn around to hang their hat on a petition that doesn’t follow any practices. If you are unfamiliar, here are few key problems with the petition:

(1) It’s a petition, not a survey. No attempt is made at selecting a representative sample and no effort is made to determine ratio of scientists who challenge global warming to those who don’t. (2) Their only standard for defining a “scientists” is the dubious requirement that one simply have a bachelors in science or engineering. Would you accept legal advice from a pre-law or have surgery performed by a guy with only an undergraduate? Then you shouldn’t take an undergrad in physics to be a serious authority on atmospheric physics. To wit, 31,000 people with a bachelors or more in science is less than 0.3% of the ~10 million (Americans alone) who have a bachelors in science. Even the 9,000 PhDs the survey boasts is small when you consider that ~30,000 new PhDs in science are awarded every year. (3) Most of the PhDs who signed the petition are in fields that have nothing to do with climate science.  The number of self-identified climatologists who sign the petition is 39, with maybe one or two thousand in related fields (if you want to be generous). I don’t know how anyone can say with a straight face “31,000 scientists support our petition. Of those, 39 actually study the subject matter relevant to the petition”. Peter Hadfield has a great video on youtube explaining what it means to be “an expert”.

We won’t even get in to issues with the tactics of the survey or the fact that the survey was at one point signed by Perry Mason, the Doctors from MASH, and even the Spice-girls.

The AMS Survey

The op-ed goes on to quote an American Meteorological Society survey (the paper can be found here). Say Bast and Spencer,”only 39.8%…said man made global warming is dangerous.” They must be hoping that their readers don’t actually bother to read the survey. In response to how harmful or beneficial global warming would be over the next 150 years, 38% respondents answered “very harmful” but they neglect to mention an additional 38% answered “somewhat harmful”. That’s 76% who believe the consequences of warming will range from “somewhat harmful” to “very harmful”. Even this understates the level of agreement because the 24% who believe that the consequences will be benign includes many AMS members who do not qualify as scientists or climate experts. Of the respondents, 38% do not have a PhD. Only around 23% of the respondents claim to publish primarily on the topic of climate science. In fact, the main finding of the survey is that climate consensus is much higher among those who actually have the relevant expertise.

Brey and Von Storch

Bast and Spencer go on to cite a survey by Brey and Von Storch. This is one of my favorite surveys on the topic. I happen to think that it paints a pretty accurate picture of the state of the field. It covers a wide range of topics. Rather than a simple “yes” or “no” choice, the questions are answered on a scale from 1 to 7. And, they have a good sample size and composition.

Ironically for Bast and Spencer, the level of consensus expressed in the Von Storch paper happens to be pretty strong and it agrees well with the levels of confidence expressed by the IPCC. Point-by-point, if you look at topics where there is high agreement in the survey, they correspond to findings that the IPCC attributes with “high confidence”. The points where there is little agreement in the survey correspond to findings that the IPCC cites as having “low confidence”.

Throughout their editorial, Bast and Spencer  have been focusing on the question of how many climate experts believe in “harmful, man-made global warming”.  For some reason they neglect to report the results of this survey on those very questions (gee, I wonder why?). Let’s look at the results:




Why I Don’t Like the “97% number”
Polls inevitably make oversimplifications and understate the complexity of the issues. The 97% number gives the impression of a monolithic “climate orthodoxy” that isn’t there. In reality, climate scientists hold a spectrum of views, and many subjects are still hotly debated. It is difficult to reduce everything to simple yes-no questions, and I am skeptical of the precision implied by using 2 significant digits in the 97% number. That said, there are certain key findings of climate science supported by so many data and so many lines of evidence that everyone in the community has moved on. Everyone, that is, but guys like Prof Spencer (although even Spencer concedes some amount of greenhouse warming).

But you don’t have to take my word for it

To any nonscientists who doubt the level of agreement among climate scientists: I challenge you to make a list of scientific institutions, pick a random sample and see for yourself how hard it is to find an active climatologist who does not believe the earth is warming (a few percent) or who doesn’t think humans are responsible for a good chunk of the last half-century warming (<10%) or  who thinks that the consequences will be benign (probably <10%). Pick a few journals and regularly read the articles (if you need help, recruit a scientist friend).  You will quickly see just how marginal your outlook is.

Can We Move On Now?

Policy makers and the public need to know that essentially no one in the climate science community questions the premise that world has warmed over the last century. Policy makers and the public need to know that the vast majority of the climate science community are convinced that more than half of the warming since the 1950s is driven by manmade causes. Policy makers and the public need to know that the vast majority of climate scientists feel that the implications of this man-made warming are likely to range from somewhat harmful to very harmful. Instead of peddling doubt and innuendo, Spencer and Bast should actually help to make constructive improvements to the process of polling the community. Ultimately, if they want to nitpick over the exact percentage that constitutes a “vast majority” of climate scientists, more power to them. But, if they’re trying suggest that there isn’t any majority among climate scientists on these three key points, then they’re just being counterfactual.


1. For the entirety of this article, I will define “the main findings” of science on climate change as being (1) the earth is warming (2) most of the warming since the mid-20th century is and will continue to be driven by man-made causes (primarily greenhouse gases) and (3) that the consequences of continued warming will incur economic and human costs.

How to research research [pt1 – intro]

Scientific issues are playing an ever greater role in our society: from the innovations that generate so much of our wealth to the very preservation of human life. Technological innovations produced by science have a huge impact on our lives: sometimes for better and sometimes for worse.

People are right to be skeptical of of new scientific findings. People are right not to take scientific posturing on authority alone. People are especially right to ask questions. I think that most scientists love nothing more than tough questions asked out of genuine curiosity and concern.

Unfortunately, true skepticism is very difficult to separate from it’s lesser (and more irrational) cousin: doubt. When I encounter websites or media sources that present phony skepticism or when I see misguided skepticism from opinionated non-scientists it makes me sad: both because it muddies the topic in question and because it confuses people about how the scientific process works. I find it disheartening to see so much bad information and -in some cases- disinformation is out there. Scientific issues are complex. Scientific language is couched in an open and careful admission of uncertainties. Both of these things make it incredibly easy for partisans to spin and distort our work. An informed scientific reader should always be aware of this.

Skepticism is an essential part of the scientific enterprise. But, many people seem to think that skepticism means being skeptical of others. One of the most important points in the scientific method is self-skepticism. Being hyper aware of our own biases and predispositions is the first step in overcoming them. The purpose of all of the controls in the scientific method isn’t to guard against the biases of others. Researchers put these controls in place to protect ourselves against our own bias. I truly believe that if more people operated with self-skepticism, we as a society would be better able to handle the complex problems that increasingly loom over our society.

The skeptical approaches of the scientific method do not have to apply only to scientists who are doing original research. A non-scientist, trying to understand a scientific issue can use these methods to keep his inquiry as objective and open-minded as possible. In a past article I gave an outline for how to fact-check web rumors. In the next series of posts, I would like to provide some thoughts for how to dig for the science buried the clutter of these rumors. My goal is to provide instruction on how to research research.

At the end of the day, the important question is not about how much research you did, but how you did your research. What is your research process? Do you have one? Ideologues typically research like lawyers: actively seeking out the facts that support their position, and disregarding or minimizing the facts that weaken their cases. Given the complexity and breadth of scientific issues, it is always possible to find experts and data to support any proposition. A person is capable of convincing themselves of just about anything. And, for anything they hear, they can probably find a rebuttal. But, is that data and are those experts representative of the whole of the knowledge on a subject?  To properly get the pulse of a field, you need to think less like a lawyer and more like a scientist: you need to prefer seeing a thing for how it is, and not how you want it to be. This is the essence of what we will hash out in the following articles.

This post is just an introduction to what will hopefully be a series. The second two posts are more-or-less finished. So I’m going to try to post at least one a week, with the first follow-up coming on Monday. Also, I’ve been experimenting with sound and video, so who knows what crazy things I may try.

Bursting the “Filter Bubble”

View gaps

I’ve mentioned many times that it is our nature to preferentially seek out information that tells us what we want to hear, while ignoring those facts which are inconvenient to our beliefs. It is an insidious problem.

The problem of this “selection bias” is bad enough by itself. The scary thing is that the web makes matters worse: search engines like google and Facebook have built in “predictive filtering”. Information is presented to us according to predictions of what we would like to see (based on our past search behavior).

Selective filtering by search engines and web pages is a nice idea on paper. In practice, it serves to further insulate us from information that would challenge our beliefs. We end up living in an information bubble where we receive only the information that we want to hear. Not only do we choose to ignore challenging facts, but google (and others) already makes the choice for us. It becomes all the easier to get entrenched in our over simplistic ideological world views. Perhaps this media trend is part of the reason for the growing political polarization in America.

In 2011, Eli Pariser gave a great Ted Talk on the subject. I highly recommend it.

Just yesterday, my sis-in-law Andrea sent me an interesting article in the MIT technology review on a group who is working to solve this problem:

Another interesting solution I’ve seen is a browser-plugin that can connect readers on a particular website to webpages that rebut the arguments on the site:

In both cases, I’m glad to see people working on solving this problem.

My own two cents

I think this is an excellent idea. However, I would caution both of these approaches not to present the world as a dialectic, a two-sided “point-counterpoint”. People tend to sort themselves into two opposing camps on any issue, but the real world does not work that way. The real world shows much richer complexity than dualisms allow. On any issue, there is a wide range of possible views and available facts.

I think it would be interesting, not only to expose people to “opposing” viewpoints, but to also expose them to atypical “hybrid” viewpoints: like animal rights activists who belong to the NRA, or social conservatives who want to legalize pot.

People are more receptive to contrary evidence from those closer to their worldview than they are from people who are polar opposite of their worldview. You have to ease someone into new ideas. And, the best way to shake people out of their box is to show them that the world has many more than just two possibilities available to it.

Can science be applied to questions about the past?


A friend of mine recently wrote on his blog post that “we can’t apply the scientific method to the past” [1] .

I admit to sometimes being a little knee jerk with such comments: I often encounter them in religious circles, used as a way to dismiss particular scientific findings that appear to contradict religious doctrine. It is all too easy, by saying “science cannot go there” to throw out contradictory evidence with the flick of the wrist. In the process, one throws out a large number of topics that have long been considered science: geology, paleontology, cosmology, etc.

In any case, knee-jerk reactions are never worthwhile. His question is very interesting and a good teaching opportunity to review what science is, and to discuss why these subjects are indeed legitimately scientific. So, here we go.

Nobody Was Around Back Then

One argument often put forward is that we cannot make scientific statements about events that happened before anyone was around to witness them. This is a slippery slope: why stop with the past? It is true that nobody was around to witness the dinosaurs, but indeed nobody has ever seen a proton! Yet, I’ve never heard anyone question the existence of protons.

The vast majority of contemporary science happens far outside the realm of direct human experience (which covers an incredibly narrow band in the Universe). Most of science relies on instrumentation and techniques that extend our reach beyond the narrow world of our limited direct experience. These techniques have worked to great success, allowing us to see many orders of magnitude smaller than the wavelength of visible light, many orders of magnitude beyond our planet, and many orders of magnitude in the past. What makes any of these studies scientific, is not whether people are around to see them, but rather they are scientific because they correctly follow the methods and protocols of science.

So What Are the Protocols Of Science?

It is not my intention in this article to provide a full review of the scientific method. I happen to really like Peter Hadfield’s youtube video on the subject. Let’s just focus on some of the key points:

Is there data? Of course. We have fossils, mountains, volcanic rocks, erosion, radiometric abundances, ice cores, seasonal sediminent deposits, tree rings, etc.

Are there quantifiable, testable theories that explain the above phenomena? Of course: theory of plate tectonics, theory of evolution, nuclear theory,  etc.

A key point in science is the idea of falsification. Scientific theories must be capable of tests that can falsify them if they are incorrect. Is this the case for “historical” science? Of course. For example, there used to be many competing hypotheses regarding the extinction of the dinosaurs. As evidence piled in, the majority of these were falsified and the discussion focuses around a very limited number of hypotheses (for example, see The K-T ExtinctionThe Chicxulub Debate and Deccan Volcanism expressing several competing but much more circumscribed theories on dinosaur extinction) [2].

More importantly, have these theories made novel predictions a priori (without knowing the outcome) that were later tested and validated? Yes! Scientists have made countless thousands of predictions regarding evidence of past events that should be discoverable in the geological and fossil records. These predicted observations have since been independently and repeatedly confirmed.

A hypothetical example: a geologist discovers the site of a huge volcanic eruption. The date of the eruption is estimated from the location of the site in the geological column. Multiple samples are sent to several radiometry labs. Without knowing the origin of the samples, these independent groups consistently date the sample to a period in time that agrees with the geologist’s original estimate. Researchers look in the ice core record to find a dust layer consistent with aerosol particles from a volcano. Knowing when the eruption happened, they count back the layers of seasonal ice deposits to the range of years predicted by the radiometric dating. They find a large eruption in exactly the right spot. Similar observations are made in other geological records. Isotopic analysis shows all of these layers in multiple ice cores around the globe and in various sediment deposits to match the composition of material found at the site of the eruption. A real life example of this hypothetical described in more depth in this article on The Toba Super Eruption and Polar Ice Cores and this one on The Lake Malawi Sediment Chronometer and the Toba Super Eruption [3]. How is this not science?

But you cannot conduct controlled experiments?

There is a common misconception that to do science, you must be able to conduct laboratory experiments. By such an argument, one could say that “mountains exist” is not a scientific proposition, simply because it is impossible to create and observe a mountain in the laboratory. On the contrary, some sciences are based almost exclusively on field observation. This, of course, does present a number of unique challenges. Performing a “control run” is impossible with historical events, but it is still possible to implement “controls” against researcher bias. However, the unique challenges of historical science are understood and addressed by the experts in these fields. For an excellent in depth discussion, read this article [4].

One interesting point made in Ref [4] is that establishing whether an event happened is an easier task than deriving a generalizable causal model for a phenomenon. Saying “B happened” is much easier than saying “phenomenon A generally causes phenomenon B through mechanism X”. The many trials and the control runs in laboratory science are necessary in order to disentangle the possible causes of an effect. These are unnecessary in establishing the particularities of a single historical event. A criminologist must study the profiles of many serial killers and many normal individuals in order to understand what makes a serial killer. A forensic detective need only establish that a pattern of murders is consistent with a single serial killer. There is no arguing that both of them are studying the same phenomena. The difference is that one looks forward in time (the criminologist) and the other looks backward (the forensic detective).

What if the laws of nature have changed in time?

As I discussed in my post on coherence between many lines of evidence, scientists don’t just look at a single measurement or a single technique. We compare different measurements to each other. The more and varied these measurements are, the more constrained is the system we are trying to understand. To go back to that previous example: If the laws of radioactive decay had changed significantly over the last hundred thousand years, we would see them diverge from the tree ring or the ice core record. One would be hard pressed to come up with a scenario where completely independent physical processes such as seasonal melting patters in ice, seasonal sediment deposits in lake beds, chemical processes, etc would vary perfectly in concert so as to render the change in radioactive decay rates undetectable. Rather, if all of these independently corroborate the story told by a radiometric measurement, then I can rest assured that the decay rates must have been pretty constant with respect to a wide variety of other physical processes. These sorts of calibrations (including volcanic eruptions) have been performed many thousands of times by many thousands of scientists for nearly a century. The majority of evidence from our past works out to be very consistent with science as we know it, and across all major fields of science.

But You Are Taking on Faith That Different Scientific Principles Should Behave Coherently?

It is not necessary to take the coherence of physical law on faith. The proof is in the pudding. Science is an empirical endeavor. We value a model on: does this model explain the data? Can this model effectively elucidate new observations that we hadn’t thought to look for? If the model works, we have a good theory.

The coherence of natural principles in the past is demonstrated by the fact that our scientific theories are able to make coherent statements about them. If natural law were incoherent in the past, or even inconsistent with modern science, then our theories would not be able to make sense of the observations: something as simple as comparing carbon dating with tree rings would just break down and give divergent or nonsensical answers.

At the end of the day, it is always true there are certain implicit assumptions built into a scientific analysis. This is as true for science of present phenomena as it is for past phenomena. But the goal is:

1) Minimalism in assumptions
2) Hyper-sensitive awareness of those assumptions and their possible consequences.
3) Constantly testing those assumptions: either through direct measurement or by working out their consequences. Never taking those givens for granted. Not accepting them on faith or just because they “feel right”.

Few non-scientists will ever appreciate the degree to which scientists take these principles seriously. We spend our every day thoroughly and systematically seeing these principles applied. I wish more people could experience the work it takes to perform a precision measurement in science.

Maybe the laws themselves all changed coherently?

Imagine a society with a gold-based currency. Now imagine I told you that the value of gold per-gram has doubled. Now imagine further that the prices in this economy simultaneously doubled across the board. The price of an apple would be twice as expensive, but the value of a gold coin would also be twice as big. If an apple cost 3 gold coins before, it would still cost 3 gold coins. Since all of the relationships between money and price remained the same, a person would be unable to detect any meaningful change.

As in the above metaphor, science studies the interrelationships between various natural phenomena. If all of these phenomena change in a way that preserves those interrelationships, than at some point it becomes meaningless to say that anything was different. At the end of the day, if the science of today can make predictive statements about evidence from the past, then one can say that the science of today is perfectly good at describing said evidence.  One can say that science is still valid, and it is merely a matter of philosophical speculation about “the nature of reality” to delve any further. After all, our brains could be in “The Matrix”, in which case all of our science (past and present) is purely fictional.  Such speculations may be valuable themselves, but they go beyond science and into the realm of metaphysics.

A person can always invoke “unknown unknowns”, or speculate as to the existence of some mechanism for fooling the science. Such claims are often made without doing any of the hard work to provide a mechanism or demonstrate it through evidence based inquiry. As a scientist, I always leave room for the “unknown unknowns”. But, I have to be pragmatic and I have to live in a world where some things are better known than others. We understand many events of the past better than we know of many happenings in the world today.


The fact that a topic is based on field observation rather than laboratory experimentation does not mean it isn’t science. Moreoever, direct eye-witness human contact is not a precondition for science. Science is a about building precise, numerical theories that explain what is known and make verifiable predictions of phenomena that were previously unknown. The latter of these two criteria is essential. The ability of a theory to predict phenomena that nobody previously thought to look for is the key to making sure that said theory is not merely being tweaked or fudged to match the known data alone.

Most scientific frameworks for explaining past events satisfy these criteria in spades. While cosmology of the early Universe is still subject to big unknowns, natural history going back a few hundred million years is well known not only in broad strokes, but even in terms of exact details: periods of glaciation at exactly the calculable times of wobbles in the earth’s orbit,  mass extinctions, asteroid impacts, and volcanic eruptions.

Scientific paradigms in biology, astronomy, physics, geology, chemistry, and climatology are able to precisely and consistently describe phenomena in the geological record on multiple levels of complexity: ranging from the fundamental (eg nuclear decays or thermoluminesence or rates of fossilization) to the macroscopic (eg tree growth, statistical changes in fossil morphology, glacial growth, or solar evolution). Having read some of the primary literature (though I don’t claim to be an expert), it is impossible for me to understate how vast the evidence is. Anyone who tells you otherwise is either lying to you or deceiving themselves. I urge my readers not to take me on my word. Learn about it. It’s really cool stuff! And, I’m glad to help you out with references or explanations on technical matters (to the best of my ability), and to refer you to experts when I’m in over my head.

Further Reading

[1] Patently Jewish – Folly of Faith, Folly of Reason

[2] R. Cowen- The K-T Extinction , and G. Keller – The Chicxulub Debate , Deccan Volcanism

[3] The Toba Super Eruption and Polar Ice Cores and The Lake Malawi Sediment Chronometer and the Toba Super Eruption. Check out the primary sources for further reading.

[4] C.E. Cleland, “Historical Science, Experimental Science and the Scientific Method“, Geology (Nov 2001) v. 29; no. 11; p. 987–990. Click here to read the full article.