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http://earthguide.ucsd.edu/virtualmuseum/climatechange2/07_1.shtml http://earthguide.ucsd.edu/virtualmuseum/climatechange2/07_1... On a geologic timescale, CO2

• lifeformed 8y ago
  But it's just talking about the past 800,000 years.
  • Diederich 8y ago
    Can you expand on that?
  • Paraesthetic 8y ago
    Do we even know what happened in the last 100 years? The problem with predictive analysis is that it presumes things have always continued along a trend line. This is always unlikely and basing predictions off this minute piece of the picture is like doing a 5000 piece jigsaw guessing the picture from one piece of the puzzle.
• Ancalagon 8y ago
  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 8y ago
    Yeah but Pilfer's point is the levels in the last 800,000 years are abnormally low in the last 200 million year period.
• nixpulvis 8y ago
  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 8y ago
    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.
    • graeme 8y ago
      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.
    • pharrington 8y ago
      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 8y ago
        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.
        • nixpulvis 8y ago
          The sad truth is nobody actually knows what's going to happen. We can only read the signs.
• pharrington 8y ago
  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 8y ago
    >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 8y ago
      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 8y ago
        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.
        • gameswithgo 8y ago
          obtuse levels are high here. goal posts moved on a goal post already moved. goal post was being moved back
        • dwaltrip 8y ago
          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?
• eloff 8y ago
  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.
• thaumaturgy 8y ago
  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-hastened-the-syrian-war/ https://www.scientificamerican.com/article/climate-change-ha...
  • Pilfer 8y ago
    >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.
• deleted 8y ago
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• mikeash 8y ago
  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?
• tim333 8y ago
  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.