5 ms·

No no, that just won't do. Math and modeling doesn't allow us to draw conclusions about things we can't directly observe. Someone had to be there and directly c

No no, that just won't do. Math and modeling doesn't allow us to draw conclusions about things we can't directly observe. Someone had to be there and directly count the co2 molecules with their own eyes or it doesn't count as evidence.

maxxxxx 10y ago
I actually was the same for the dinosaurs. Have you seen any and written it down?
Turing_Machine 10y ago
Okay, I'm all ears (or, technically, eyes, since I'm reading this). How does a 400,000 year old ice core show anything about conditions 4 million years ago? Please be specific.
- Turing_Machine 10y ago
  P.S. you can assume that I've taken differential equations and graduate-level courses in computer modeling and simulation, if that helps.
  - chc 10y ago
    You can edit your comments instead of replying to yourself over and over.
- Turing_Machine 10y ago
  Now I see mention of an 800,000 year old core in that article. That's still not 4 million, or anything like it.
  - nkurz 10y ago
    I was initially dubious of the "4 million year" quote, but the quick searching I did doesn't turn up anything credible that would contradict it, and did turn up many estimates that concur. I don't know enough to evaluate his methods, but Mark Pagani at Yale seems to have published a number of papers that give estimates going back 40 million years: http://people.earth.yale.edu/cenozoic-evolution-carbon-dioxide http://people.earth.yale.edu/cenozoic-evolution-carbon-dioxi... And this paper 2005 paper by Dana Royer provides an overview of a few hundred estimates going back 500 million years: http://droyer.web.wesleyan.edu/PhanCO2(GCA).pdf http://droyer.web.wesleyan.edu/PhanCO2(GCA).pdf
- tstactplsignore 10y ago
  There are specific mineral records that covary strongly with CO2 levels over that 400,000 year period. However, these mineral records go back millions of years - therefore, we can use the known relationship to predict how CO2 levels have changed in the past. These are known as "proxies" in paleoclimatology, and can be used to estimate past CO2 levels, O2 levels, temperature, and other attributes of Earth's climate. When multiple independent proxy estimates agree with each other, we can somewhat safely assume we are not too off-target. This field is constantly getting updated, but these proxies are usually in decently good agreement with each other. I think that the paper below is a good overview of the science involved. I'm not an expert in the field but this paper is from 2006 and likely now the field has added some more accurate proxy paleo-CO2 reconstructions. http://droyer.web.wesleyan.edu/PhanCO2%28GCA%29.pdf http://droyer.web.wesleyan.edu/PhanCO2%28GCA%29.pdf
  - Turing_Machine 10y ago
    Yeah, I know what a proxy measure is. That's not what the OP said, though.
    - splawn 10y ago
      If you knew they used proxy measures then why didn't you simply explain that to the OP rather than pretend you didn't understand? However, I am glad you asked because it caused me to investigate and learn something new.
- splawn 10y ago
  Nice catch! It doesn't... the ice core measurements do show that it was waaay lower 800,000 yrs ago at 185ppm. To go beyond that they use other methods that are less accurate, but still good enough to at least get in the ballpark. Its admittedly a huge ballpark... 4M yrs is the conservative estimate while 25M yrs is the upper limit of what makes sense. Here is my source: https://psmag.com/when-s-the-last-time-our-co2-levels-were-this-high-128b19503511#.wntfjaxei https://psmag.com/when-s-the-last-time-our-co2-levels-were-t...
dang 10y ago
Please don't do this here. We detached this subthread from https://news.ycombinator.com/item?id=11919106 https://news.ycombinator.com/item?id=11919106 and marked it off-topic.

maxxxxx 10y ago

I actually was the same for the dinosaurs. Have you seen any and written it down?

Turing_Machine 10y ago

Okay, I'm all ears (or, technically, eyes, since I'm reading this). How does a 400,000 year old ice core show anything about conditions 4 million years ago? Please be specific.

Turing_Machine 10y ago
P.S. you can assume that I've taken differential equations and graduate-level courses in computer modeling and simulation, if that helps.
- chc 10y ago
  You can edit your comments instead of replying to yourself over and over.
Turing_Machine 10y ago
Now I see mention of an 800,000 year old core in that article. That's still not 4 million, or anything like it.
- nkurz 10y ago
  I was initially dubious of the "4 million year" quote, but the quick searching I did doesn't turn up anything credible that would contradict it, and did turn up many estimates that concur. I don't know enough to evaluate his methods, but Mark Pagani at Yale seems to have published a number of papers that give estimates going back 40 million years: http://people.earth.yale.edu/cenozoic-evolution-carbon-dioxide http://people.earth.yale.edu/cenozoic-evolution-carbon-dioxi... And this paper 2005 paper by Dana Royer provides an overview of a few hundred estimates going back 500 million years: http://droyer.web.wesleyan.edu/PhanCO2(GCA).pdf http://droyer.web.wesleyan.edu/PhanCO2(GCA).pdf
tstactplsignore 10y ago
There are specific mineral records that covary strongly with CO2 levels over that 400,000 year period. However, these mineral records go back millions of years - therefore, we can use the known relationship to predict how CO2 levels have changed in the past. These are known as "proxies" in paleoclimatology, and can be used to estimate past CO2 levels, O2 levels, temperature, and other attributes of Earth's climate. When multiple independent proxy estimates agree with each other, we can somewhat safely assume we are not too off-target. This field is constantly getting updated, but these proxies are usually in decently good agreement with each other. I think that the paper below is a good overview of the science involved. I'm not an expert in the field but this paper is from 2006 and likely now the field has added some more accurate proxy paleo-CO2 reconstructions. http://droyer.web.wesleyan.edu/PhanCO2%28GCA%29.pdf http://droyer.web.wesleyan.edu/PhanCO2%28GCA%29.pdf
- Turing_Machine 10y ago
  Yeah, I know what a proxy measure is. That's not what the OP said, though.
  - splawn 10y ago
    If you knew they used proxy measures then why didn't you simply explain that to the OP rather than pretend you didn't understand? However, I am glad you asked because it caused me to investigate and learn something new.
splawn 10y ago
Nice catch! It doesn't... the ice core measurements do show that it was waaay lower 800,000 yrs ago at 185ppm. To go beyond that they use other methods that are less accurate, but still good enough to at least get in the ballpark. Its admittedly a huge ballpark... 4M yrs is the conservative estimate while 25M yrs is the upper limit of what makes sense. Here is my source: https://psmag.com/when-s-the-last-time-our-co2-levels-were-this-high-128b19503511#.wntfjaxei https://psmag.com/when-s-the-last-time-our-co2-levels-were-t...

dang 10y ago

Please don't do this here. We detached this subthread from https://news.ycombinator.com/item?id=11919106 https://news.ycombinator.com/item?id=11919106 and marked it off-topic.