[Pilfer]

http://earthguide.ucsd.edu/virtualmuseum/climatechange2/07_1...

On a geologic timescale, CO2 levels were many times higher than they are today.

>In very general terms, long-term reconstructions of atmospheric CO2 levels going back in time show that 500 million years ago atmospheric CO2 was some 20 times higher than present values. It dropped, then rose again some 200 million years ago to 4-5 times present levels--a period that saw the rise of giant fern forests--and then continued a slow decline until recent pre-industrial time.

CO2 levels over the past ~5 million years are at the lowest point in over 200 million years. On a geological timescale, CO2 levels are returning to normal, not going away from it.

[thaumaturgy]

Okay, this comes up sometimes in climate-related topics, usually because of a combination of misunderstanding and a need to be the clever contrarian that's thought of something nobody else has.

The question isn't whether Earth will survive these CO2 levels. Earth will (probably) be just fine. It's common knowledge, especially among the scientists that publish claims about rising CO2 levels, that Earth has had much higher levels of CO2 and other greenhouse gases in the past, and that at those times, there was lots of life.

The question isn't necessarily even whether humans will survive much higher CO2 levels. We're resourceful, we have the ability to shape our environment. Some people will survive.

The question is how much we're going to enjoy all of the adverse effects of this global climate change. It is going to cause or contribute to a lot of natural disasters: hurricanes, tornadoes, extreme storms, droughts, flooding, massive wildfires. There are going to be migrations. Wars. There are some solid arguments that climate change contributed to the Syrian civil war [1]. Many species are going to disappear as they fail to adapt quickly enough to the changing environment; it will take much longer for new species to take their place. We will see, for example, an environment with fewer butterflies and more mosquitoes -- many more.

Nobody is going to get out of this unscathed. It's going to cause widespread political and economic instability and unrest. Even if you manage to find yourself a nice little spot untouched by the most direct effects of climate change, it's going to cause enough suffering in enough other parts of our globally interconnected human society that you'll see the costs somewhere. The US spent a record $306 billion on disaster response last year. Where do you think that money comes from?

[1]: https://www.scientificamerican.com/article/climate-change-ha...

[TangoTrotFox]

I think your framing of the question is very fair and absolutely how the topic should be considered. But at the same time, I think you're assuming much more from the average person than is realistic when you state that whether Earth (and implicitly humanity) will survive or not, is not the question. People are becoming radicalized in everything. And radicalism tends to be intrinsically connected with ignorance.

See the top of this thread (well currently at least) for a line of discussion where somebody not only thinks climate will imminently lead to earth becoming uninhabitable but wondering how and where people could survive [away from Earth] until the planet does become habitable again. Or consider the fact that the comment you're responding to, though factually accurate and contextually relevant, is being downvoted for stating facts that mitigate this sort of hysteria. Sure, it's a sample of one - but I'm sure a survey of the views in this thread will show the question is indeed far more elementary than the nuanced and accurate view you're discussing!

[thaumaturgy]

People are becoming radicalized in large part, maybe even entirely, because of forums like this one. A really good article along these lines was submitted to HN, but unfortunately didn't get much traction: https://www.rollingstone.com/politics/news/all-american-nazi...

I think people can handle nuance just fine. Since everyone's gotten it into their heads that policing online discussions is exactly the same as censorship and limiting free speech, it's up to us, the participants, to restrain ourselves from the radicalizing shouting matches that usually happen on so many topics.

> See the top of this thread (well currently at least) for a line of discussion where somebody not only thinks climate will imminently lead to earth becoming uninhabitable but wondering how and where people could survive [away from Earth] until the planet does become habitable again.

I'm not seeing that anywhere in the comments on this article. Can you link to it?

> Or consider the fact that the comment you're responding to, though factually accurate and contextually relevant, is being downvoted for stating facts that mitigate this sort of hysteria.

Well, no. I disagree that it's relevant, and hope at least some of the downvotes are for that reason alone. "Stating facts" doesn't automatically make something relevant; good statements of relevant facts would have been, "the researchers didn't take ____ into account during the 800,000 period they're talking about", or, "there's another paper by respected researchers that disagrees with this one", or, "I know a lot about this field and I think I see an error in their methodology", or, "this is all correct but there's no cause for alarm because [body of evidence that global warming is somehow beneficial]" (it's not).

It's also not mitigating hysteria. There are good reasons to be extremely alarmed for our future generations. That's not a hysterical position. Some people may be couching it in alarmist statements, but given the opposing number of people who still believe that all of this data is an outright lie anyway [+], that's sort of unavoidable for political topics.

[+]: Including HN, during the CRU email breach a few years ago, where the popular opinion was that climate researchers were fabricating data so that they could get more money for further research.

[jessaustin]

I'm not seeing that anywhere in the comments on this article. Can you link to it?

This [0] seems pretty close to that description.

There are good reasons to be extremely alarmed for our future generations. That's not a hysterical position.

Very few people "believe" strongly enough to invest based on that belief. Why hasn't Bezos or Soros or whoever started buying lots of land in northern Saskatchewan, or shorting land on the coasts?

[0] https://news.ycombinator.com/item?id=17008013

[thaumaturgy]

Ah, thanks. Yeah, not sure I'd agree totally with that particular comment.

> Why hasn't Bezos or Soros or whoever started buying lots of land in northern Saskatchewan, or shorting land on the coasts?

Because (a) it's complicated (https://www.bloomberg.com/news/features/2018-05-02/the-u-s-c...) and (b) investors are famously short-term thinkers and as is evident in some of the discussion here, the effects of global warming are just slow and opaque enough to fool a lot of people into thinking they don't exist.

...and this is granting that investor interest is a good way to evaluate how sound the science is on some subject, and I don't think that's a position I'd agree with.

[Pilfer]

>It's common knowledge, especially among the scientists that publish claims about rising CO2 levels, that Earth has had much higher levels of CO2 and other greenhouse gases in the past, and that at those times, there was lots of life.

This isn't common knowledge at all among non-scientists. Most people have no clue that CO2 levels were many times higher than today, and that earth and the ecosystem in general were just fine. Scientists may be aware of this fact, but why don't they inform the general public of this? Take the submitted article for example. Instead of publishing an article stating, "CO2 levels are higher than 800,000 years ago; but are likely lower than they were at any point from 20-200 million years ago" they only leave in the scary, doomsaying first part and neglect to inform the second part. It is the equivalent of looking at a 24 hour geological clock and only telling people about the past minute while neglecting datapoints from minutes or hours ago. Why aren't scientists informing the public of the historical data?

I understand why the climate change community may not want to bring up this point (it detracts from other issues) but people should be aware of this fact. Humanity, and life in general, will survive increased CO2 levels.

>The question isn't whether [X], it's whether [Y].

I am paraphrasing, but that's largely what your comment is saying. The article premise and its title, is about [X], where [X] is CO2 levels. It seems like the response to historical CO2 levels is to change the topic.

Edit: I don't want to reply to several comments, so I'll respond here.

Why do I believe the discussion should inform people about historical CO2 levels? Largely because I firmly believe CO2 emissions will not decrease through 2040. The incentives to cut emissions are just not there. Petroleum is simply too useful as a resource. The current projections I have seen predict 500ppm by 2050, and likely 600ppm by 2100. Given those numbers, I ask myself the question, how likely is it that humanity will face extinction in the next century? How should I interpret these numbers?

Given the geological data, I find it reassuring that biology and life on earth survived for hundreds of millions of years with CO2 levels between 1000-2000ppm. It means that increased CO2 levels will not cause the extinction of humanity.

[gameswithgo]

>. Humanity, and life in general, will survive increased CO2 levels.

In the few past instances when temperatures increased this fast there were mass extinction events.

Yes, life can exist on a warmer earth just fine. But rapid change kills a lot of things.

Scientists don't focus on informing people that the earth used to be much warmer and it was fine, because they are focusing on the fact that rapid change is dangerous.

[Jweb_Guru]

The sun is also measurably brighter and hotter than it was when CO2 levels were significantly higher, meaning we should expect greenhouse effects to be more severe. CO2 levels aren't the only thing that contribute to climate. Additionally, while in the past the levels have been much higher, the rate of change in CO2 levels was never nearly this swift in the geological record--it's the sudden change that has many people worried.

[Pilfer]

I did not bring global temperatures into the discussion as I don't believe they pose as serious a threat as increased CO2 levels. Wikipedia has a nice graph showing estimated global average temperatures over time https://en.wikipedia.org/wiki/File:All_palaeotemps.svg . Please note the log-time scale.

The graph shows that between 10-250 million years ago, global temperatures were 1-12° C higher than they are today. Given that current projections, which include the 2% relative gain in solar irradiance, expect 3-4°C warming by 2100, the geologic temperature record suggests such increases are not detrimental to life on earth. Let us recall that life was thriving during the Jurassic and Cretaceous periods, when temperatures were 5-10°C higher and CO2 levels between 1000-2000ppm. Global temperatures today are actually lower than than average, on a geological timescale.

>the rate of change in CO2 levels was never nearly this swift

No, you can't conclude this. You cannot show there was no other a period in Earth's geologic history where CO2 levels rose by 150ppm (or 150%, whichever is not relevant) in less than 200 years. The geologic record is not detailed enough to make such a claim. It is unknowable if there was a series of major volcanic eruptions that caused CO2 levels to rise rapidly.

And sudden change has always been a part of climate and evolution. Rapid change can occur in just a few decades. For example, the Sahara wasn't even a desert 10,000 years ago. Also see punctuated equilibrium.

[zaarn]

> You cannot show there was no other a period in Earth's geologic history where CO2 levels rose by 150ppm (or 150%, whichever is not relevant) in less than 200 years

That assumes the CO2 is also gone just as quickly. But I doubt that would happen unless you can show a natural process that could not only increase the CO2 level by 150ppm but also decrease it by 150ppm just as quickly.

[Brockenstein]

Your argument seems to be that everything is OK because things always change and conditions have been much more extreme in the distant past. And other people are arguing that these sorts of extreme changes may have very real consequences that can dramatically effect human civilization and stability and we're doing very little to prepare or blunt the blows.

[graeme]

People are concerned mainly about how CO2 will affect humans + our current ecosystem. On that measure, 800,000 years is a relevant timeframe: it covers when our civilizatiom arose, when humans left africa, etc

I do think it would be good if people knew that CO2 was even higher in the past. But, that doesn't make this article wrong. An article can't cover every single topic, and earlier CO2 in the non-human era is just tangentially related.

[thaumaturgy]

Alright, I want to point-by-point rebut your comment, but I'm going to take a step back instead.

What is your goal here?

Every argument has some kind of goal, some position or point of view that it wants to express. Yours appears to be, "CO2 accumulation is no big deal as long as at least a few people survive". (Contextualizing your own statement that, "Humanity, and life in general, will survive increased CO2 levels".)

But I don't want to assume that that's your argument, because it would be a wildly irrational one to make. So let's bring your actual position out into the light.

--

edit in response to your edit:

> Largely because I firmly believe CO2 emissions will not decrease through 2040.

Maybe. But they could, except for all of the politics and arguments around this that is still preventing large-scale efforts to reduce global emissions.

> Petroleum is simply too useful as a resource.

It has been useful. Humanity likely could not have reached its current state of technological development without easy access to vast amounts of energy in the form of coal and oil.

But its usefulness is waning. Countries and organizations are more often using it to influence the economies of other countries. A lot of suffering is happening in Venezuela right now, and oil is a major contributor to that; a lot of damage was done to Gulf Coast not long ago, and even if you place no value at all on natural ecosystems, it also impacted a lot of livelihoods that depended on fishing and tourism in the area. Depending on your point of view, the most recent Iraq war killed, maimed, or displaced a lot of people for the sake of controlling oil. Tensions between Europe, US, and Russia right now can also trace their causes back to the distribution of natural gas.

And none of this is taking into account the predicted effects of a warming global climate. Many -- many! -- more people are going to suffer and die.

> I find it reassuring that biology and life on earth survived for hundreds of millions of years with CO2 levels between 1000-2000ppm. It means that increased CO2 levels will not cause the extinction of humanity.

There are a lot of different conditions that satisfy "survival", and many of them are pretty awful.

--

Since global warming / climate change is such a politically charged topic, let's try reframing it.

Let's say there is a hypothetical global disease for which nobody has a natural immunity. We'll use some variant of the Black Plague for this gedankenexperiment. Right now it is responsible for killing an estimated few hundred thousand people a year worldwide [1], and costs several hundreds of billions of dollars each year worldwide [2]. We could be committing more resources towards reducing the impacts of this disease, but right now, this is a level of suffering and expense which enough people are totally okay with.

This disease is expected to gradually worsen though, and in the not very distant future, begin killing millions and harming millions more. We may still be able to mitigate a lot of the effects of the disease in the future, but we'll still have the same costs for developing new technology to fight it, plus we'll have much higher costs for dealing with the effects of it.

The Black Plague killed 30% to 60% of Europe's population in the mid-1300s [3], and now it's coming back, just more slowly.

Would your position then be, "it's no big deal, we survived it once before"?

[1]: https://www.thedailybeast.com/climate-change-kills-400000-a-...

[2]: https://news.nationalgeographic.com/2017/09/climate-change-c... -- this doesn't include worldwide numbers; I'm using a conservative extrapolation here.

[3]: https://en.wikipedia.org/wiki/Black_Death

[ScottBurson]

> Humanity [...] will survive increased CO2 levels.

I don't know that we can take this as a given. It would have been easier two or three hundred years ago; now we have industrial civilization and 7.3 billion people, the combination giving us an unprecedented ability to do damage to the ecosphere. I can imagine a scenario in which climate change leads to political unrest which leads to wars — we may already be seeing some of this, and it could get a lot worse — that eventually spirals out of control into thermonuclear war. Unlikely? I sure hope so! But I don't think we can rule it out completely.

Sure, the cockroaches will survive. But that's not much consolation.

I think we need to figure out a way for all of humanity to work together on this problem. If we fail to do that pretty soon, I don't think it will bode well for our doing it in the future either. Continued denial and fractiousness will make the nightmare scenario more likely.

[lurker456]

Humanity may survive, but our civilization likely won't. It relies on cheap energy and a stable climate, both are under threat. Good luck manufacturing a MRI machine when you're struggling to grow enough food for next year.

[Diederich]

> It seems like the response to historical CO2 levels is to change the topic.

How does a detailed discussion about CO2 levels 100m years ago help push us toward drastically cutting emissions now?

[eloff]

The article talks about this being the highest point in the last 800K years, but you're right that geologically speaking the levels are quite low for our planet.

The problem is life takes a long time to adapt, including us silly humans who build our cities on the coast. Just because CO2 levels have been higher before does mean the process will be a pleasant one.

It may well involve the extinction of large numbers of species, and large numbers of humans (never all humans as some people seem to be fond of saying.) It could even possibly trigger collapse of civilization in extreme enough scenarios where methane from the oceans and tundras is released in a feedback loop.

So yeah, you're factually correct, but missing the point.

[Ancalagon]

No, the article says the CO2 levels are at their highest in the last 800,000 years. Its literally right there in the title of the post.

[tim333]

Yeah but Pilfer's point is the levels in the last 800,000 years are abnormally low in the last 200 million year period.

[mikeash]

If I’m interested in the survival of human civilization, which has been around for less than 10,000 years, how is it useful to consider that CO2 levels were much higher 200 million years ago?

[pharrington]

Yes, the Cambrian explosion indeed was an even wilder change in environment and ecosystem than what we're going through now. A hypothetical human time traveler, however, wouldn't survive a hypothetical time travel back to that.

[Pilfer]

>A hypothetical human time traveler, however, wouldn't survive a hypothetical time travel back to [the Cambrian explosion].

I assume you are referencing about CO2 levels. Yes, around ~500 million years ago, CO2 levels reached 10,000ppm, which would be hazardous (but not fatal) to a human traveler. However if you pick a point between 300 million years ago and today, when CO2 levels were at 1000-2000ppm, a human traveler would have no problem surviving in that environment. Heck, it is even possible to hit those CO2 levels in a modern day warehouse or office that is poorly ventilated.

Increased CO2 levels are very survivable and do not mean the end of the human race.

[epistasis]

The question isn't whether some humans will survive or not, but where they will survive, and how expensive it is to adjust to that change.

[Pilfer]

Which is moving the goalposts and changing the question. He's asking if a "hypothetical human time traveler" could survive hundreds of millions of years ago, and based off historical CO2 data, it could be possible.

[dwaltrip]

You are picking pedantic arguments instead of focusing on the actually important themes, which isn't productive or useful

Let's get everything on the table. Are you actually okay with dozens of millions to hundreds of millions of people dying -- and many others suffering immense drops in quality of life -- as a result of human-caused climate change? Despite the fact that we have the capacity to heavily mitigate such risks?

[gameswithgo]

obtuse levels are high here. goal posts moved on a goal post already moved. goal post was being moved back

[tim333]

I think that's true although it's also true that rapidly increasing CO2 now seems a dangerous experiment with our only planet.

As an aside noting the downvotes on the above comment I sometimes question if that stuff is a good idea. I can see the point that mentioning high CO2 levels may not be a problem could be dangerous as the masses will keep burning CO2 but trying to drum up panic isn't working that great as illustrated by the "highest point in 800,000 years" thing. From an engineering kind of view point I feel you should look at things as neutrally as possible though I guess from a political view point maybe not.

[nixpulvis]

From the same site:

> All we can say is that, over the last 400,000 years, there seems to have been a positive feedback at work: whenever the climate became warmer, carbon dioxide and methane rose and helped make the climate even warmer.

[Pilfer]

Fair, but that doesn't detract from the point that CO2 levels maintained 1000-2000ppm for over 100 million years. This was during the Jurassic and Cretaceous periods, when life was thriving on earth.

Present CO2 levels are low on a geological timescale.

[gshubert17]

Due to stellar evolution, the solar constant is at its highest on a geological timescale.

https://archive.org/details/nasa_techdoc_19820009158

Back in the Mesozoic Era, the Sun was about 2% cooler than it is today. The extra CO2 back then added a helpful (for most life) greenhouse effect. Now, both the relatively high CO2 level and the rapid rate of increase are unhelpful.

[jessaustin]

That link performs a calculation based on some fairly back-of-the-envelope physics assumptions. Its conclusion:

Roughly one-half of the solar luminosity increase occurs during the last 2 billion years but there is no evidence for a parallel increase in the Earth's mean surface temperature. Indeed, isotopic studies of the Precambrian samples by Knauth and Epstein (ref. 12) indicate that the mean surface temperature has been decreasing during this time. Clearly, there is a need for further studies of the effects of crustal movements and volcanism, biological activity, etc. on the long-term evolution of the Earth's climate. At present, it appears that the effects of solar evolution are still buried in the "noise" due to other uncertainties in paleoclimatic models.

Is there anything since 1981 with more definitive conclusions? Is there any study that has attempted to measure sun output directly or indirectly, rather than simply calculating output based on the sun's age?

[Jweb_Guru]

Thank you. Nothing annoys me more than people who bring up the fact that CO2 used to be much higher without mentioning that the sun was cooler. It leads to a very misleading picture.

[graeme]

How well would that work for humans? 2000 ppm is well above the threshold when we start to find negative cognitive effects. And I imagine CO2 in buildings would be more like 3000-4000 ppm.

This is leaving aside sea level rise hurting infrastructure, crop failures due to shifting weather, and areas becoming regularly above 35 degrees wet bulb.

[nixpulvis]

That doesn't change the fact that there are adverse effects we are noticing, which CO2 is a contributor to.

Its also worth noting that a lot of what has scientists concerned is the rate at which we are seeing these changes.

[pharrington]

That is a true statement. Another true statement is that Earth's greenhouse gases are basically a trace compared with Venus's. Another true statement is that the current human causal rate of CO2 emissions will rapidly change our environment to one unsuitable for human life.

[eloff]

Source on that last one? Even the worst climate change predictions don't create an earth unsuitable to human life. Hostile changes, sure. Unsuitable? No.

[pharrington]

You're right, I shouldn't have said that. Unsuitable for human civilization is what I should have said.

[eloff]

That would only be in the worst case scenarios, and even then only a transitory condition. You can't keep humans down forever, sooner or later we'd rise again. It's debatable what it would take for civilization to collapse, and how long it would take to recover. But I think there's little doubt that recover it would.

[nixpulvis]

The sad truth is nobody actually knows what's going to happen. We can only read the signs.

[lifeformed]

But it's just talking about the past 800,000 years.

[Diederich]

Can you expand on that?