<p>I was reading <a href="http://www.climatecentral.org/news/we-just-breached-the-410-parts-per-million-threshold-21372" rel="nofollow noreferrer">this article</a> today, and I saw this chart of atmospheric carbon dioxide levels for the past year:</p>

<p><a href="https://i.sstatic.net/w56Tv.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/w56Tv.jpg" alt="Carbon dioxide May 2016-April 2017"></a></p>

<p>The chart shows a decline in atmospheric carbon dioxide levels from roughly June-October, a cycle that appears to be consistent across <a href="https://www.esrl.noaa.gov/gmd/ccgg/trends/full.html" rel="nofollow noreferrer">many years</a>: <a href="https://i.sstatic.net/oOuuk.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/oOuuk.png" alt="Longer term atmospheric carbon dioxide"></a></p>

<p>Why does this cycle occur? It looks like the period of decline coincides with the season of greatest plant growth in the northern hemisphere. Or is it that energy demand rises so much during the northern-hemisphere winter that the CO2 levels for the entire atmosphere are quickly changed?</p>

CC BY-SA 3.0
2017-04-21T05:44:39.280Z
I've heard this explained by the Amazon rain forest, sometimes called the "lungs of the planet".    http://english.cntv.cn/program/china24/20130411/106725.shtml   But I don't know if that's truly the reason, or if it's a combination of factors, perhaps ocean absorption/plankton growth could be a significant factor.
userLTK
CC BY-SA 3.0
2017-08-15T08:55:13.797Z
It may depend on where it is measured in the atmosphere. If they measure it at a same height it will differ according to season because the height of troposphere/atmosphere itself changes due to differences in pressure. This in turn leads to differences in transportation of CO2.
St.Clair Bij
<atmosphere><climate-change>
Why Do Carbon Dioxide Levels Vary Seasonally?
Kupyn
# Why Do Carbon Dioxide Levels Vary Seasonally?

(Asked by: username_0 on 2017-04-21)

I was reading [this article](http://www.climatecentral.org/news/we-just-breached-the-410-parts-per-million-threshold-21372) today, and I saw this chart of atmospheric carbon dioxide levels for the past year:

[![Carbon dioxide May 2016-April 2017](https://i.sstatic.net/w56Tv.jpg)](https://i.sstatic.net/w56Tv.jpg)

The chart shows a decline in atmospheric carbon dioxide levels from roughly June-October, a cycle that appears to be consistent across [many years](https://www.esrl.noaa.gov/gmd/ccgg/trends/full.html): [![Longer term atmospheric carbon dioxide](https://i.sstatic.net/oOuuk.png)](https://i.sstatic.net/oOuuk.png)

Why does this cycle occur? It looks like the period of decline coincides with the season of greatest plant growth in the northern hemisphere. Or is it that energy demand rises so much during the northern-hemisphere winter that the CO2 levels for the entire atmosphere are quickly changed?

**Tags:** atmosphere, climate-change

> **Comments:**
> **username_1**: I've heard this explained by the Amazon rain forest, sometimes called the "lungs of the planet".    http://english.cntv.cn/program/china24/20130411/106725.shtml   But I don't know if that's truly the reason, or if it's a combination of factors, perhaps ocean absorption/plankton growth could be a significant factor.  
> **username_2**: It may depend on where it is measured in the atmosphere. If they measure it at a same height it will differ according to season because the height of troposphere/atmosphere itself changes due to differences in pressure. This in turn leads to differences in transportation of CO2.  

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## 0 answers

