Tracking Atmospheric Carbon Dioxide Over Geological Time
Last updated July 15, 2018
This is the first in a series of posts that describe Earth's carbon dioxide levels over geological time. Writing this piece has helped me memorize important dates and numbers. I hope it helps you, too. Climate science is fascinating!
At what point in geological time did atmospheric Carbon dioxide levels match today's?
Scientists know from analyzing ice cores from Antarctica that at no time during the last 800,000 have atmospheric CO₂ levels been as high as they are today (May 2018 levels averaged above 411 ppm).
Though some scientists pin the date even farther back: between 10–15 million years ago.
What was the climate like back then?
Given the 3–5 million years ago time frame from the NASA website, that would put us in the Pliocene.
Modern humans did not exist, but Mastodons did!
Seas were between 16–131 feet (5–40 meters) higher. (Please note: I obtained these figures from the NASA Global Climate Change website, which I linked to above. These figures vary according to different sources.)
At this point, you might want to check the elevation of your community and some of your favorite places around the world. It's an interesting visual exercise.
But it was also much warmer during the Pliocene: 5.4–7.2 degrees Fahrenheit (3–4 degrees Celsius) hotter than present times.
And the poles were 18 degrees Fahrenheit (10 degrees Celsius) warmer than they are today.
atmospheric carbon dioxide levels have seasonal cycles: They rise in the Northern Hemisphere during fall and winter as plants decay, releasing CO₂. but over the growing season, late spring and summer—when plants use CO₂ in the process of photosynthesis—CO₂ levels tend to drop.
atmospheric Carbon dioxide levels over the last 800,000 years
Over the last 800,000 years, the amount of CO₂ in the atmosphere has ranged between 180–280 ppm.
Before the Industrial Revolution and during the 1800s, global CO₂ levels averaged around 280 ppm.
Charles David Keeling first measured atmospheric CO₂ at Mauna Loa in 1958: the results—317 ppm.
CO₂ levels during May 2018 averaged above 411 ppm.
You can track amounts of CO₂ in the atmosphere throughout Earth's history and keep up with the latest figures on the NOAA website, here.
Below is a short animation that illustrates how CO₂ levels have changed over geological time (NOAA). But hang in there with it because just when you think it's over, there's more! For more information, check out this page on the NOAA website.
What can we expect in the future, and why is it important?
I'm working on separate posts that will attempt to answer these questions. Please stay tuned!
Please note: My editor took off for the hills and hasn't been seen for years. If you're a journalist or scientist and find mistakes, please reach out through the contact form in the menu at the bottom of this page. I don't mind being corrected at all. Thanks!