[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?