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Ask HN: Are you a former climate change denier? What changed your perspective?
2 points by syllable_studio 84 days ago | hide | past | web | favorite | 9 comments
I'm asking this to try to learn more about the mindset of climate deniers. I want to better understand how our divided world could facilitate better dialog and move forward with urgent climate solutions. I thought it would be interesting to pose this question to the community.

If you're after a dialogue, perhaps the term "denier" might be seen by those who are skeptical as a little pejorative?

I'm sure I'll get flak for this. I'm not a climate change 'denier', but I'm sure I'll be called that by some. In fact, I 'believe' in climate change, meaning that the climate is changing. Because I believe the climate is always changing. When people use the term "climate change" these days, they (IMO) assume that the climate has been steady state for millennia until recently (last 50 years?), and that it's only been changing recently, that it's a sudden thing, and that it's all our fault.

The climate has changed, waxed and waned many, many times over the ages. There was an ice age that ended about 10,000 years ago. There was a warming period, followed by a cooling period in the middle ages (search Little Ice Age on wikipedia). Where were all the carbon emissions then? There's plenty of evidence that the climate changes all the time, and there is no 'normal' climate, no 'set point' where it is 'supposed' to be at -- that's simply not how climate works. We don't really know how it works, all of the factors involved. But there is no specific set point that the climate is 'supposed' to get to and maintain. What kind of silliness is that?

Yes it is changing, getting warmer, but there's a lot of scare mongering going on that we're at fault, and I don't think we've figured that out yet. Who's to say it won't start cooling off again sooner or later? If you're old enough to remember, in the 1970s (and maybe 1980s) we were scare mongering over the coming ice age, a global cooling that was going to freeze us all out. How ironic we're now in the midst of the opposite.

I will say that one very positive thing about all the scare mongering is that we're pouring money into clean fuels and methods, which is brilliant -- we should have been doing that all along, and if it takes some fear to push that, great.

For those who condemn people like me who aren't convinced that the warming trend is all our fault, be very careful about your science. Just because 4 out of 5 scientists or 99% of scientists agree or believe climate change is happening (it is) and that it's our fault (that's not clear yet), doesn't make it true. The number of people who believe in God doesn't improve God's chances of existing, any more than the number of athiests who disbelieve in God makes God disappear. Belief is not reality. Belief is belief. Reality is reality. The two are not the same, and they are not related or dependent on each other in any way. But too many of us get hijacked by our beliefs and go nuts because we think it's realty.

Also understand that one published study is regurgitated with the same sensational headlines in 1,000 or more news outlets, making it 'appear' that there is a consensus of all these news outlets. No, it's the same piece of news, sensationalized and then repeated a thousand times over, not a 1,000 different news outlets reporting on a 1,000 different, separate studies that all came to the same conclusion. We have some serious mental biases that come from repetition -- stop watching the news! (How many news stations report how many planes landed safely? None. How many report the one plane crash that happened? All of them, in gory detail.)

Recall that cholesterol used to be the big threat to our health these past 40+ years. Surprise! We're now finding out over the past few years that it ain't so. A whole generation or two of scientists had to pass on before we got to today where cholesterol is not considered a cause of CHD. Back in the 'fat and cholesterol cause CHD', you didn't get your science funded if you weren't taking that position as truth, and if your research wasn't geared towards proving exactly that. Go read up on how Alzheimer's research has been stymied for decades because scientists refused to accept that the beta amaloids were a symptom of the disease, and not its cause.

Be careful of the agendas of those who say climate change isn't happening. But also be wary of those who claim to know that it is, and that it's all our fault -- they have their own agendas.

And when anyone, especially a scientist, says "the science is settled", you are now in the realm of a dogmatic religion, closed-minded to any evidence that contradicts the belief in the 'faith'.

So, climate getting warmer? Seems to be, yes. Carbon emissions causing it? Hmm. Not so sure yet. Humans causing it? Again, no clear cut evidence that shows how this warming period is due to us that explains how all the other warming periods came about that weren't us. Will it never cool off again? No one knows, but it's done so in the past, so the balance of probabilities is yes. Unless we really are the cause, and there's a tipping point where we can never see a reversal, and we pass that point. Sure, it's possible. It's also possible we'll be struck by an enormous chunk of rock that wipes out the human race, which I think is a serious threat, but for which we don't seem to be putting a lot of energy and funding into providing early warning and a means to do something about it.

Whether we are to blame or not for the warming climate (as of today), I hope the hysteria continues for another decade or two -- the motivation it provides for developing cleaner energies and products won't likely happen otherwise, just like had we not had the Cold War, the space race would not have happened, and we'd not have landed on the Moon. (Sorry, moon-landing deniers. It really happened.)

hi @meretext, thanks for engaging in this dialog, I appreciate you taking the time. This is really interesting to me. You're clearly smart and passionate about this. And it sounds like you are an evidence-based thinker. It sounds like maybe you've been bombarded with a lot of media but maybe haven't been given very good evidence, does that sound right?

For example, what do you make of this chart shown on the nasa.gov page? It shows the cycles that you're talking about, but then it shows how our situation is incredibly different from any other cycles over thousands of years. https://climate.nasa.gov/evidence/

So given evidence like that, what is your reaction? (I'm really not trying to convince you or troll you or anything, I'd love to learn more about how you think and what your arguments are). Do you think that the information isn't convincing or that it's a conspiracy? Do you feel certain that human-made climate change isn't real, or are you skeptical but open to the idea?

I'm also open to the idea that climate change is NOT real if I was confronted with compelling evidence. Though, I just haven't seen any so far...

Last question if you'll allow me: Do you think there's a chance that climate change could be a disaster? If so, do you think it's worth doing something about it? Or at least confirming whether or not it is real? Or do you feel convinced that there is nothing to worry about?

Thanks again, Eric

If you're going to make me work, I'm going to make you think.

There are seven (7) issues I've identified with the graph you provided as evidence. See if you can identify those same issues.

Find and download the study that the graph on the https://climate.nasa.gov/evidence/ page that you provided says it is based on. It's short, four pages. I downloaded, printed and hand-annotated the study, scanned it in and I will provide a link to the study with my annotations after. I will also answer all of the questions you've asked me, again, after. Promise.

Here's the link to the unannotated study:


   or the PDF version, which I prefer:

Good hunting!


Eric, I assume you don't want to do the work, or you don't want to allocate time doing so. So I'll close this out.

First, I want to be clear about the context for my challenging that slide you pointed me to located at https://climate.nasa.gov/evidence -- I am not challenging whether climate change is real or not, and I'm not challenging whether humans are or aren't the cause of it.

I am challenging the specific evidence you point to, and not blindly accepting a graph without questioning what data it is based on and how that data was analyzed. The problem with providing a slide like that to people as evidence is that it fits what they already believe, and so no one questions the source that generated these results. Slapping an atmospheric CO2 value in ppm onto a graph taken from a study that measures CO2 values in ppmv from ice cores isn’t science.

The slide you point to on that page shows a graph from the study mentioned in the graph’s caption, and purports to show historical atmospheric CO2 over the past 800,000 years, to measurements of the actual CO2 taken from actual current atmosphere. I have read and annotated the study, and I’ll accept that data as accurate for now and won’t challenge what is in that study.


1. The graph you point to is not the graph that the referenced study supplied -- it is that graph with a portion added on the end that did not come from the study. It looks like someone took the graph from the study, and tacked on the ‘1950 on’ CO2 levels measured from the actual atmosphere (which are from the NOAA Mauna Loa measurements).

2. The “1950s on” label is inaccurate. The study states that accurate measurements of atmospheric CO2 did not begin until 1958. It’s minor, but it’s important to be accurate here.

3. How do we know that the CO2 in an ice core can be directly compared to a measurement taken of actual, live atmosphere? How do we know there isn’t some process whereby the CO2 in an ice core shows up as lower than an actual atmospheric measurement? That may be in the end notes of the study, but I’m not going to do the work to dig through that now. It’s something that needs to be validated, if it hasn’t already, before being accepted as fact.

4. The study says that CO2 levels and arctic temps are strongly coupled (correlated). Correlation isn’t causation. Correlation is correlation. We see that two things are correlated, and our brain immediately sees a causal connection. STOP DOING THAT. Cholesterol is correlated with coronary heart disease, but it is not a cause of CHD.

5. Despite the study stating that CO2 levels and arctic temps are strongly coupled (correlated), it also states that there were significant deviations between Temperature and CO2 levels multiple times over that period, meaning that there were multiple times where the CO2 levels were not correlated with arctic temperatures. Clearly then, CO2 levels are not always in line with what you would expect temps to be if CO2 were driving the temps higher -- what mechanism is causing temps to be what they were despite CO2 levels suggesting the temps should be different? Maybe CO2 levels were higher, but the temps stayed lower, meaning that more CO2 was released from some other mechanism -- or maybe something else prevented temps from going higher despite increases in CO2.

6. Let’s assume that there is a strong correlation in the evidence of the study’s data that actually points to there being a true cause and effect result between CO2 levels and temperature levels. You still have to prove what is causing what, not just that one causes the other. You have to show whether temperature rise is the result of increased CO2 in the atmosphere, OR increased CO2 in the atmosphere is the result of increasing temperatures. Even if CO2 increases show up prior to temperature rises, it still doesn’t mean CO2 is causing the temperature rises. CO2 could be a leading indicator of future temperature increases, not a cause of them, meaning that whatever mechanisms are increasing the temperature, they are first triggering increases in CO2 in the atmosphere. That could mean that both CO2 levels and temperature rises are both caused by a something else.

7. By far the biggest error I find in the slide you pointed to: They used different unit measurements!!! The ice cores measure CO2 in ppmv, the NOAA atmospheric measure of CO2 is in ppm. They are not the same! It is quite possible that if you could convert the ppm of the NOAA data into ppmv units, it might fit right in to the study’s graph! I haven’t proven anything, I’m saying it’s now an open question, that the slide you pointed me to is a result of someone tacking together two separate graphs of data that is measured in two different units. You cannot compare them directly. See here:


I wouldn’t be surprised if you can convert the 400 ppm CO2 value into ppmv and that it comes out to around the 280 ppmv CO2. Try these calculators:



That could make the NOAA data comparable to the units of the study’s data, and plot that and it might fit the study graph perfectly, and not the slide you showed me. Even if it doesn’t, it’s not proof of the opposite. The CO2 in the ice cores is in water; the CO2 in the NOAA measurements is in gaseous form. That alone might account for the difference, but still, I question whether CO2 measurements in water can be compared to CO2 measurements in air without some conversions and adjustments for units, or other factors.

So I’ve poked holes in that graph you provided as evidence. It isn’t proof that climate change isn’t happening, and it isn’t proof that humans are not to blame -- it is simply showing that the evidence in that graph you provided has serious problems, and should not be used as ‘evidence’ until those problems are resolved. But it will be passed around and people will believe it is evidence and not question it, because they've already decided what the truth is and aren't interested in challenging evidence that fits their already selected belief.

I highly recommend watching Michael Crichton’s talk:


Over and out.

I'm not sure what your point is here.

Ok, Eric is not a climate scientist (or if they are, they're perhaps not a very good one). And one graph that they've pointed to as demonstrating what actual climate scientists are concerned about has some problems too. Fine.

But really --- for many (most?) questions, many (most?) people are unable to evaluate the evidence themselves, and instead fall back to the consensus of actual experts.

And I think that's perfectly reasonable behavior: being an expert in everything is impossible.

In this case, there are plenty of people who are experts. Trained, experienced, knowledgeable people. And by an overwhelming majority, they think there's a big problem here.

Now there are cases where orthodoxy in science, in part worsened by cultural or religious factors, has led to a consensus that was subsequently shown to be unsupported by later, better, evidence and analysis. It's possible that this is the case here, and your skeptical approach is not entirely unwarranted.

But the consensus view of the probable outcomes is pretty dire. And that's probably a quite conservative prediction, because those scientists who have risked the backlash of talking about what they personally think is likely, paint a significantly worse picture.

At what point should we, as humanity, decide that the risk is worth altering our behavior, if not now?

The point?

Eric asked me: "...what do you make of this chart shown on the nasa.gov page? It shows the cycles that you're talking about, but then it shows how our situation is incredibly different from any other cycles over thousands of years. https://climate.nasa.gov/evidence/ So given evidence like that, what is your reaction?"

I responded that based on my assessment, this is not good evidence to support a claim that climate change (e.g. global warming) is 'real' and is human caused, and I specifically laid out why.

That's it. That was the point.

If you want to respond to any or all of those specific items, and show where I might be mistaken, great.

Note that I did not make any claims as to whether climate change (e.g. global warming) is or isn't 'real', nor whether humans are or are not involved or the cause. If that's what you got from my reply to Eric, then you're reading more into my response than I wrote. I think we should be analyzing and challenging all evidence, supporting any claims and any position. That's what science is supposed to be about, IMO. I made that clear:

"First, I want to be clear about the context for my challenging that slide you pointed me to located at https://climate.nasa.gov/evidence -- I am not challenging whether climate change is real or not, and I'm not challenging whether humans are or aren't the cause of it."

I do think we should be working on renewable energy sources that are cleaner, reducing environmental pollution, and so on, because that really makes sense regardless of what's going on with the climate.

In response to your other comments:

I'm not a climate scientist either, but I don't think you need to be one to analyze data and evidence. Read the study and the NOAA data that the evidence Eric pointed me to is based on, and see for yourself. As for whether most people have the time, I agree, most probably don't, but Eric specifically asked me to look at this data; I think it fair to ask him to do the work to analyze it as well.

Your comment along the lines of "most climate scientists believe X" doesn't really say anything other than that most climate scientists believe X. So? Most experts used to believe the Sun revolved around the Earth. As I've said prior, consensus is not evidence. That many experts believe something is presented as evidence may be very true. But that doesn't say anything about whether what they believe is actually true.

"An argumentum ad populum (Latin for 'appeal to the people') is a fallacious argument that concludes that a proposition must be true because many or most people believe it, often concisely encapsulated as: "If many believe so, it is so. Other names for the fallacy include appeal to (common) belief,[2][3] appeal to the majority,[4] appeal to the masses,[5] appeal to popularity,[6][7] argument by consensus,[8] authority of the many,[8][9] bandwagon fallacy,[7][10] consensus gentium (Latin for 'agreement of the people'),[10] democratic fallacy,[11] and mob appeal.[12]" (From WikiPedia I think).

As for the consequences being dire, we'll see.

I recommend you watch the Michael Crichton talk I gave the link for.


I'm not sure you'd like to continue this discussion. I'm kinda interested in your point of view, but ... I don't want to impose on you, so feel free to quit.

While you say: "I responded that based on my assessment, this is not good evidence to support a claim that climate change (e.g. global warming) is 'real' and is human caused, and I specifically laid out why.

That's it. That was the point."

I don't dispute that this particular piece of "evidence" might be problematic. I'm not prepared to invest the time to make an independent determination one way or the other, frankly. You have, and I have no reason to doubt that you've raised valid issues.

I do have some issues with your apparent dismissal of expert consensus. I think "an argumentum ad populum" is mislabeling. When the people who hold the opinion are experts in the field, and the overwhelming majority of them say the same thing, choosing to dismiss that as some sort of mob delusion seems wrong.

The vast majority of experts tell me the Earth is an oblate sphere. There are some people who claim it's flat. Do I dismiss those experts? Or, perhaps more to my point, do you?

As I said: there are times in history, both recent and not so recent, when the consensus of experts has been incorrect. Groupthink is real, political pressure is real, lazy thinking is real, and even fallacious understanding of reality is real.

That said, I do not believe that I, while perhaps a skilled technologist, have the expertise to form a judgement contrary to that of literally thousands of experts here.

Do you?

Or are you simply attempting to ensure that when evidence is presented, it is immaculate?

You then say "As for the consequences being dire, we'll see". That also suggests to me that you do doubt the expert consensus? Of course, literally, you're right: the predicted outcomes are only predictions, and the climate is a massive complex system. The only way to be sure is to wait and see what happens.

The Michael Crichton link is 3:32 long. Would you be willing to summarize his point before I wade through that?

If you're not prepared to invest the time to make an independent determination one way or the other, and you want to rely on the consensus view of experts, that's fine, there is nothing inherently wrong in that. Just understand that your belief that they're right doesn't mean they're right, and consensus is not evidence. That's all. Using "most experts agree" as an argument is an argumentum ad populum by definition. It's a fallacious argument to make, because you're saying that the number of people (experts or otherwise) who believe something to be true, means that it must be true. Using that argument to try and convince someone of a position to take is a fallacious argument. If you say I don't know the truth of it, but I'm going to side with the consensus, that's at least being clear.

You don't have to have the expertise to form a judgement contrary to that of literally thousands of experts here for them to be actually incorrect. Note how you're using language to make it seem more 'true' and 'weighty': "judgement contrary to that of literally thousands of experts" -- again, implying that the vast number of experts that believe something to be true makes it more true than if fewer experts believed it. That's precisely the fallacy I'm talking about. You just made an argumentum ad populum, when you're fully made aware of what that is and understand what that is, you still couldn't help it. The more experts that believe something to be true, the more that will jump on the bandwagon because that many already think it true. That may be part of what's happening, because I don't think anyone actually knows what is happening and why yet. There are plenty of examples in history, even recent history, of that type of groupthink happening, and the Ancel Keys Dietary fat theory of coronary heart disease is one of them. Once he said that was the cause, then others believed him, took his study as showing causation, rather than correlation, and the overwhelming consensus was that saturated fat and cholesterol caused heart disease. And they were all wrong, the consensus was wrong, his evidence was inaccurate.

Here's how it seems to me right now, and I'll use an analogy: if you had a consensus of financial experts saying that Apple stock was going to go to $600 a share, and it does, were they 'right' or were they 'lucky'? Because there is no way, no matter how much 'evidence' they have, that they can know that Apple will reach $600. They don't know what will happen, they are speculating. Go read up on counterfactuals.

Yeah, I'm beating a dead horse here, repeating myself so I'll stop now and close.

Because I poke holes in evidence that supports the theory of climate change does not mean I'm against that theory -- it doesn't mean I'm for it either. I can take the position of, "I don't know", and that is my position. But I can still poke holes in evidence from both sides of that debate, while still holding the position that I don't know whether the theory is accurate or not. I can't poke holes in a 'consensus', because a consensus is not evidence. Belief in something is not evidence. Evidence is evidence, and our interpretation and understanding of such complex systems is poor at best.

Climate change may be happening, and it may be due to us, and it may have dire consequences. Or it may not, and we'll be fine, the climate will start to cool, and we'll see maybe we don't know all the mechanisms at play or how they interact.

Watch the first 20 mins of the Crichton talk. You'll know if you want to watch more by then. We think we know things, but we really don't when it comes to things as complicated as climate.


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