Trends in atmospheric CO2 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.



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?
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.