<p>The explanation is that human activities are not the only processes that affect atmospheric composition.  </p>

<p>Last time CO2 levels were higher than today was 10-15 million years, during the Miocene epoch. During the Miocene, sea level estimated to be 100 feet higher and the global average surface temperature estimated to be 10°F warmer than today.</p>

<p><a href="https://i.sstatic.net/6ofFH.jpg" rel="noreferrer"><img src="https://i.sstatic.net/6ofFH.jpg" alt="Sea Level Change over time"></a></p>

<p><a href="https://i.sstatic.net/qA2Ly.png" rel="noreferrer"><img src="https://i.sstatic.net/qA2Ly.png" alt="Temperature over time"></a></p>

<p>References:</p>

<p><a href="https://www.e-education.psu.edu/earth107/node/901" rel="noreferrer">Miocene Sea level graph.</a></p>

<p><a href="http://www.climateemergencyinstitute.com/climate_history.html" rel="noreferrer">Temperature over time graph.</a></p>

<p><a href="http://www.climatecentral.org/news/the-last-time-co2-was-this-high-humans-didnt-exist-15938" rel="noreferrer">www.climatecentral.org</a></p>

<p><a href="http://science.sciencemag.org/content/326/5958/1394" rel="noreferrer">Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years</a></p>

CC BY-SA 3.0
2017-03-07T06:48:59.913Z
What other things affected climate change during that time? I read that position changes of the continents and warmer climates were the reasons for changes in global circulation patterns but what caused such warm climates? Was it also related to plate tectonics?          References: http://www.ucmp.berkeley.edu/tertiary/miocene.php
Math4life
CC BY-SA 4.0
2022-07-21T23:24:19.997Z
Wow, a log scale would have made more sense.
Spencer
CC BY-SA 3.0
2017-03-06T20:52:29.283Z
2017-03-06T21:11:20.813Z
2017-03-06T21:11:20.813Z
Earth Science Expatriate
<p>Recently I've been working on a debate for climate change and I'm working on a rebuttal statement but then I came across many different sites that claimed that there were higher CO<sub>2</sub> levels before there was even industrialization or a substantial amount of CO<sub>2</sub> being made from humans. I just need an explanation on how this happened. </p>

<climate-change><co2>
How was it possible that CO2 levels were higher nearly 650,000 years ago?
Math4life
# How was it possible that CO2 levels were higher nearly 650,000 years ago?

(Asked by: username_0 on 2017-03-06)

Recently I've been working on a debate for climate change and I'm working on a rebuttal statement but then I came across many different sites that claimed that there were higher CO2 levels before there was even industrialization or a substantial amount of CO2 being made from humans. I just need an explanation on how this happened.

**Tags:** climate-change, co2


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## 1 answers

### Answer by username_1 on 2017-03-06. Score: 5 | Accepted answer

The explanation is that human activities are not the only processes that affect atmospheric composition.

Last time CO2 levels were higher than today was 10-15 million years, during the Miocene epoch. During the Miocene, sea level estimated to be 100 feet higher and the global average surface temperature estimated to be 10°F warmer than today.

[![Sea Level Change over time](https://i.sstatic.net/6ofFH.jpg)](https://i.sstatic.net/6ofFH.jpg)

[![Temperature over time](https://i.sstatic.net/qA2Ly.png)](https://i.sstatic.net/qA2Ly.png)

References:

[Miocene Sea level graph.](https://www.e-education.psu.edu/earth107/node/901)

[Temperature over time graph.](http://www.climateemergencyinstitute.com/climate_history.html)

[www.climatecentral.org](http://www.climatecentral.org/news/the-last-time-co2-was-this-high-humans-didnt-exist-15938)

[Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years](http://science.sciencemag.org/content/326/5958/1394)

> **Comments:**
> **username_0**: What other things affected climate change during that time? I read that position changes of the continents and warmer climates were the reasons for changes in global circulation patterns but what caused such warm climates? Was it also related to plate tectonics?          References: http://www.ucmp.berkeley.edu/tertiary/miocene.php  
> **username_2**: Wow, a log scale would have made more sense.  

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