What's up guys, Rosh here, and welcome to part two of my rebuttal to Dr John Robson's A Historian Looks at Climate Change. In part one, we looked at these four arguments, so if you're curious about any of these topics and haven't seen the video, then go ahead and watch it first. If you have seen it, welcome back. Today we'll be picking up where we left off, and addressing John's remaining claims. So, at the end of part one, John had just incorrectly suggested that the recent rise in CO2 and may be a product of ocean degassing caused by the Medieval Warm Period.
And it's the Medieval Warm Period that he talks about next. Now speaking of the Medieval Warm Period, again, as a historian, the moment I saw Michael Mann's infamous hockey stick, I said, hey, what happened to the Middle Ages? So John doesn't understand why the Medieval Warm Period, a period which, as the name suggests, was characterized by a warm climate in the Middle Ages, is apparently missing from Michael Mann's temperature reconstruction.
So let's address this. The first question we have to ask ourselves is how extensive the medieval warm period actually was. And perhaps this is something John can help us with.
Here's a map. Let's see which regions John can demonstrate the medieval warm period occurred in. So I have known since I was quite young that the Middle Ages was characterized by warmth, by abundant harvests, and by the kind of cultural and geopolitical conditions that led to a flowering of arts and other institutions. That's when the great cathedrals were built.
That's when universities were invented. That's when hospitals appeared. And it's also earlier in that period when the Vikings made their voyages of discovery, which I grant you were a mixed blessing to the people they discovered and then stole their stuff and burned down their villages. Hmm.
That's not the greatest spread, is it? John's examples are all clustered around the North Atlantic, and if we look at a global temperature reconstruction for this time, this is precisely where the warmth appears to be concentrated. That's not to say that the medieval warm period was purely a North Atlantic phenomenon, there is enough evidence to suggest that overall the planet did experience above average temperatures during this time. But as you can see, the warmth varied by region, and different regions experienced this warmth at different times. On the whole, global average temperatures were roughly comparable to those of the early 20th century, and if we compare them with the present, the difference is quite dramatic.
So the evidence that the warmth of this period was regionally variable and globally subtle compared to that of today. And if you look at the wide margin of error around Michael Mann's hockey stick, it's not particularly surprising that such a subtle warm period is not visibly obvious. Separate studies have shown more pronounced warming during this time, but even then it's not comparable to that of today.
What's more important is that multiple, independent studies have all validated Michael Mann's overall conclusion. that the warming of the late 20th century is unprecedented in at least the last thousand years. Anyway, John stays on this point for a while, and rather than critiquing the methodology of man's study, something which has been criticised in the literature before, he instead seems to focus on trying to prove that the medieval warm period existed. Which is odd, because no one disputes this.
However, his next point is to argue against the idea that current warming will be bad. So again, I looked at Michael Mann's hockey stick and I said, Where's the medieval warm period and why do we think warming is bad? He then begins the talk about a meeting he had with infamous skeptical physicist William Happer.
I discovered that in addition to being a distinguished scientist, he also knows a lot about the historical evidence for the medieval warm period. He talked about the records of tithing to monasteries, which give you ideas of where crops were being grown and in what quantities. He talked about where tree lines were in the middle ages versus where they were centuries later. And in both cases, it was clear that warmth meant that plants grew better, including food crops.
Which means, you know, whatever you think of crop failure, there's really no question of the medieval warm period having existed. No, there isn't, and no one disputes this. However, I want to draw your attention to John's claim that this warmth meant crops grew better. The implication, it would seem, is that the medieval warm period was a good thing for humanity.
But, so far, John has only provided examples from Europe and Greenland. What about the other regions which experienced this warmth? What about, say, North America?
Well, there is widespread evidence that these elevated temperatures coincided with megadroughts which researchers have linked to the agricultural collapse of the civilizations which existed there. So it would seem that the medieval warm period wasn't all that great for everyone who experienced it. But I don't suppose John will let something as inconsequential as reality get in the way of his beliefs.
And then if you go back into the Pleistocene, if you look at the glaciation, you see a cycle of brief warm periods, which are nice, and long cold ones that aren't. Warm is good, cold is bad. That reminds me of another sceptic video I looked at a while back. But to be fair, in the case of glacial-interglacial cycles, John is broadly correct. Agriculture only became possible once the Earth began to warm following the last glacial period 11,000 years ago.
So yes, history tells us that temperatures fluctuate, and it tells us, yes, they have been rising since Victorian times. But again, a historian says, well, of course they have. It's a natural rebound from the Little Ice Age. It's part of a cycle of these coolings and warmings. And so it's illogical to attribute all the warming since 1860 or 1970 to human influence, as though the Thames would probably still be freezing if it weren't for that wretched Henry Ford.
History may tell us that temperatures fluctuate, but science tells us why. John hasn't even attempted to address the mechanism behind this so-called rebound, and I'd be very intrigued to hear him explain it. But let's humour him for a while.
A rebound from the Little Ice Age implies that temperatures would recover to their pre-Little Ice Age levels. But a glance at any of the numerous temperature reconstructions we have clearly demonstrates that temperatures have more than exceeded those of the medieval warm period, and indeed, any period in at least the last 4,000 years, and they may well be the highest temperatures ever experienced in human history. It looks less like a rebound and more like a leap into previously unexplored territory.
But let's look at John's next argument. And here's another historically based question about climate change. Whenever I hear people saying we're seeing levels of atmospheric CO2 unmatched in the last two and a half million years, my inclination is to say okay well What happened last time they were at this level?
You're telling me it's going to lead to runaway warming, but I look back and I see that last time it happened, the warm and lush Pliocene abruptly gave way to the chilly and barren Pleistocene, a prolonged ice age that we're actually still in. Yeah, we're currently in the Holocene Epoch, which is part of the Quaternary Ice Age. And it's just as well, because polar ice locks away a whole lot of water, which would otherwise raise sea levels.
Take the Pliocene, for example. which John correctly states was the last time CO2 levels were this high. Global temperatures were 2 to 3 degrees warmer, and sea levels were as much as 25 meters higher. Of course, we're unlikely to see anything as dramatic as 25 meters of sea level rise, certainly not anytime soon, but the point is, our civilization is adapted for the Holocene, not the Pliocene.
And by making out that an ice age began the last time CO2 levels were this high, John is being incredibly misleading. The Quaternary Ice Age only occurred once CO2 levels had declined, and long after they reached a peak of over 400 parts per million. The fact is, we are well on track to returning the planet to Pliocene conditions, conditions which humans have never experienced. And as long as CO2 levels continue to rise, the planet will continue to warm.
Since John seems to think this is a good thing, I wonder where exactly he would draw the line. After all, without emission reductions, we could easily reach a thousand parts per million, the CO2 levels of the Cretaceous. A time when the poles were completely ice-free, plant life flourished globally, and warm oceans reached 250 meters above those of today. A Garden of Eden we're simply not equipped to live in.
Though, again, judging by past patterns, the Holocene is winding down, not up. And if it is, we'll see. We're in a world of hurt that we can't fix by spraying CO2 around because it's just not the control knob on the global thermometer.
The historical record makes that abundantly clear. Well, as we saw in part one, that's not true, is it John? There's abundant evidence from the geological record which supports the idea that CO2 has driven climate change for hundreds of millions of years.
And it also sounds like John thinks the next glaciation might be imminent. But If he'd done his research, he'd have known that glacial-interglacial cycles are driven by shifts in Earth's orbit over thousands of years. They're not exactly rapid affairs. And researchers calculate that we still have another 50,000 years before the next glaciation. More time than all of recorded human history.
So, I think we can rest easy on that account. Now, on to John's next argument. And let me tell you, no historian, no scientist, no intelligent lay voter would...
Ever look at these lines and say, ah, yes, well, clearly the red one is driving the... And, yes, even if you're neither a historian nor a climate scientist, don't let anybody tell you you lack the qualifications to look at this chart and see the obvious. The obvious?
I suspect John might be employing the common sense he was so fond of in part one. But, as I pointed out then... Common sense can often be wrong. But let's follow the logic of his argument here. It seems to be that because there's no obvious correlation between CO2 and temperature, then CO2 can't possibly drive temperature change.
It certainly seems to make sense on the surface. Indeed, if we plot atmospheric nitrogen on this same graph, there is also no correlation, and no one would ever claim that nitrogen could drive temperature change. It's obvious.
Common sense, right? Except that's not nitrogen. That's the sun.
or more specifically, solar luminosity. And if you think this graph looks familiar, it should do. We discussed it in part one.
So according to John's logic, because there is no obvious correlation between solar output and temperature, the sun can't have any impact on climate either. However, as we saw in part one, if we combine the effects of both the sun and CO2 together and then plot them against temperature, we get a very good correlation indeed, because these are the two most important factors for climate, climate. over geological time. And incidentally, if John had looked at the source for the CO2 data in his graph, he would have found that it came from a 2001 study by Berner and Kotterweiler, a study which explicitly states that over the long term there is indeed a correlation between CO2 and paleo temperature. So, like in part one, John is once again contradicted by his own sources.
It's almost as if John uses common sense as an excuse to avoid critical thinking. Now, On to John's conclusion. Now, I will concede one point here about the role of experts.
If a question is purely technical, if it doesn't have political or social implications, and it really is settled, then I'm all in favor of deferring to them. If we want to know the hundredth digit of pi, let's ask a mathematician or some high school kid who's memorized the thing. If we need to know how far it is from Earth to Jupiter, let's ask an astronomer. But climate science...
is not in that category. Right, so scientists are free to measure the distance between Earth and Jupiter, and John won't take issue with them. But as soon as they measure the infrared absorption of the atmosphere, then they've crossed the line.
And they can use radiocarbon isotope dating to measure the age of a bone, but as soon as they use isotope analysis on sediment cores to reconstruct past climates, then suddenly their results are suspicious. Is it the scientific method itself that John has an issue with, or does it only become an issue when it produces results he doesn't like? Because whether he likes it or not, the same scientific process which tells us how far Jupiter is from Earth also tells us that the atmosphere is currently absorbing more energy than it is releasing, and that the Earth is warming at a rate unprecedented in the geological record.
Science isn't a pick and mix. You can't choose which evidence-based conclusions you accept, and which you don't. But John seems to think climate science is different. He goes on to say that It's a field that's wide open to debate, in which there is massive disagreement. John, every scientific field is open to debate.
That's how science works. But that debate is one of evidence, not opinion. And when the evidence from multiple fields as far apart as geology and astrophysics overwhelmingly points to the same conclusion, then it would take some very strong counter-evidence to disprove that conclusion.
John's uninformed opinions and demonstrably flawed arguments do not constitute evidence, and the fact that John doesn't like the existing evidence is not a good reason to ignore it. Whether CO2 drives climate change, whether human emissions are warming the planet, and whether they have been the primary driver of warming for the last half century are no longer in dispute. Those debates have been had, and the evidence is now so overwhelming that the debate has moved on. What is in dispute is to what extent the planet will warm in the future and what effect this will have on the climate, and even here the uncertainty is ever shrinking. The idea that there is massive disagreement about whether human activity is causing climate change and whether that climate change will continue into the future is just wrong.
And when climate alarmists tell us, quote, believe the scientists, end quote, what they really have in mind is that we should believe the scientists who share their political views and make it clear that they share them on social media. If you somehow don't believe that scientists have political views that can affect what they research and how they do their science, well, that's a history lesson for another day. I won't mention Lysenko here.
Ah yes, Lysenko, a man who famously attacked scientists whose research undermined his claims and ignored all evidence which contradicted his ideological beliefs. Seems familiar, somehow. And it also seems we've come full circle. John's back to attacking experts again. And look, I'm sure some experts are unscrupulous, some lie, and some speak about things which are well outside their areas of expertise.
And that's precisely why we should never believe experts just because they're experts. Opinion alone is not enough, and should be discarded unless it can be supported by evidence. And the notable absence of evidence in John's arguments also gives us a clue as to why he had to spend nearly half his video attacking expertise.
The evidence isn't on his side, so he has to find a way of discrediting it. And the easiest way of doing that is by going after the researchers whose work produced it. Ironically, John probably considers himself to be a sceptic. Yet true scientific scepticism requires an openness to the idea that we might be wrong, to question the conclusions of our common sense, and a willingness to change our minds in the face of evidence.
If you're not prepared to do that, you're not truly scientific. And if you rely on logical fallacies rather than observable, measurable evidence to make your arguments, then you shouldn't be surprised when people who care about science call you out on your bullshit and lack of expertise. Well that's all for today folks!
I hope you've enjoyed the video, and if you've found any logical fallacies that I missed, let me know in the comments. As always, sources are in the description, and if you want to see more of my content then don't forget to like, subscribe and smash that bell icon so you can be notified whenever I upload. Thanks for watching, and until next time, goodbye.