Today we can look back 800,000 years into the past from measurements from ice cores from Antarctica. Over this period we have secured data on how the CO₂ in the atmosphere has changed. CO₂ is considered to be the most important greenhouse gas.

The atmosphere of the past has been preserved in the snow of the Antarctic. Over time, the snow has compacted and turned into ice. The air contained in the snow got stuck in the ice in small bubbles. Then ice cores were drilled in numerous expeditions in the last decades. From these ice cores we have very direct access to the original composition of the atmosphere.

Natural CO₂-concentration: 180-300 ppm

As can be seen in the chart, the content of CO₂ in the air during this period has always fluctuated between a value of 180 and a maximum of 300 ppm. It was not until the beginning of industrialization around 1850 AD that the curve went up very steeply. And so today, in the year 2021, we have reached an unprecedented level of 420 ppm.

For almost the entire period, man found himself in the Stone Age. It was only in the past few thousand years that modern civilization began. Finally, with industrialization, the massive burning of fossil fuels, coal, crude oil and natural gas started.

The curve of CO₂ shows even more clearly than the change in temperature how strongly humans have intervened and how we have changed the composition of the atmosphere. All this resulted in a very steep increase of CO₂ especiall when compared to natural variations of this greenhouse gas over the last 800.000 years. The curve of natural CO₂ fluctuations before the industrialization also reflects the course of natural cold periods (ice ages) and warm periods in the past.

References:

Online_Resource: http://ncdc.noaa.gov/paleo/study/17975
Original_Source_URL: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/antarctica2015co2composite.txt
Study_Name: Antarctic Ice Cores Revised 800KYr CO2 Data
Investigators: Bereiter, B.; Eggleston, S.; Schmitt, J.; Nehrbass-Ahles, C.; Stocker, T.F.; Fischer, H.; Kipfstuhl, S.; Chappellaz, J.