I plotted the atmospheric CO2-concentrations to see trends and wondered especially about the phase around 1600 in the plot which I find very interesting. Etienne Godin already told me some facts in the comments of another thread, but I'm curious about more details, since I'm a newbie in this area.

enter image description here

source: https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/frank2010/smoothedco2.txt

Where I plotted the column ALL_50_full.

What do you say?

  • 2
    $\begingroup$ Hi. I am missing a question mark here. Are you asking about the so-called "Little Ice Age" ? And, as a hint, it is always good to name the source of a graph. $\endgroup$
    – user18411
    Dec 18, 2019 at 11:57
  • 1
    $\begingroup$ To emphesize my "hint": please tell us where the data is from. Not that i question it, but having a context from geography and which reservoir it comes from makes guessing easier ;-) $\endgroup$
    – user18411
    Dec 18, 2019 at 12:07
  • $\begingroup$ I plotted it myself with data of the IAC in Switzerland which published an excel sheet with that data. $\endgroup$
    – Rico1990
    Dec 19, 2019 at 16:33
  • $\begingroup$ Yep but the IAC got the data from some source (ice core, tree rings, varves, marine sediments, ...) in a place somewhere (Earth presumably, but where :-) ?) and they may have calibrated and processed it. This information would be good to have. $\endgroup$
    – user18411
    Dec 19, 2019 at 18:59
  • $\begingroup$ That's true. I used another source now and edited the article so that we can talk about the paramteres of the study too. See ncdc.noaa.gov/paleo-search/study/10437 for the source and all wanted metadata. The measurement used ppmv to access CO2-concentrations from 1000-2004. $\endgroup$
    – Rico1990
    Dec 20, 2019 at 13:41

2 Answers 2


Since CO2 concentration is responsible of temperature, that trend is related to the little ice age, where Earth cooled a little. Wikipedia article describes several possible causes for that, one of the is the answer of Keith, but others might be orbital cycles, solar activity, volcanic activity and ocean circulation.
Also is possible that is just a cycle that repeats itself each 1000 or 1500 years.

  • $\begingroup$ Thank you for your answers, I see that there are several strong theoretical positions which seem to be explications. $\endgroup$
    – Rico1990
    Dec 19, 2019 at 16:32
  • $\begingroup$ "orbital cycles, solar activity, volcanic activity and ocean circulation" might affect the temperature, but would not directly affect CO2-concentrations (except that volcanic activity would increase it, which appears to be the opposite of what the plot shows). $\endgroup$ Dec 21, 2019 at 4:41

One theory:
European Genocide of Indigenous Peoples in the Americas Cooled Earth’s Climate

The mass deaths of Indigenous American peoples 500 years ago—caused by disease and violence spread by European colonizers—was so extreme that it cooled Earth’s climate, according to a new study in Quaternary Science Reviews.
Led by Alexander Koch, a graduate student in geography at University College London, the authors said that a period of global cooling that lasted from the 16th to 19th centuries was partly caused by epidemics and warfare that killed 90 percent of the Indigenous population in just 100 years.
The devastating loss, known as the Great Dying, left 56 million hectares of farmland unattended, enabling forests and other vegetation to grow over agricultural terrains. The rewilded landscapes drank in much more carbon dioxide than the preceding farms, which reduced levels of the greenhouse gas in the atmosphere by 7-10 parts per million.

Original research this article references:
Earth system impacts of the European arrival and Great Dying in the Americas after 1492

  • $\begingroup$ That may have been a contribution, but at the same time Europe was being de-forested and more important, the signal starts in the 13th century. Other contributions may have come from: volcanoes, sunspot minima (debated), change in the north atlantic sea waters overturning ... $\endgroup$
    – user18411
    Dec 19, 2019 at 9:57
  • $\begingroup$ there were many many flaws with this study, including using modern farming practices as models of indigenous farming climatic effects. $\endgroup$
    – John
    Dec 22, 2019 at 14:29

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