Carbon dioxide in Earth's atmosphere - Wikipedia
How the World Passed a Carbon Threshold and Why It Matters - Yale E360
CO2 since 1800
Climate change: Carbon dioxide levels are higher than they've been at any point in the last 3.6 million years - CBS News
Earth's Atmosphere Passes Significant Carbon Milestone - Dan's Wild Wild Science Journal - AGU Blogosphere
Do high levels of CO2 in the past contradict the warming effect of CO2?
Atmospheric Carbon Dioxide Levels | GlobalChange.gov
Carbon dioxide concentration over time
CO2 in the atmosphere just exceeded 415 parts per million for the first time in human history | TechCrunch
Atmospheric concentrations - Our World in Data
A Graphical History of Atmospheric CO2 Levels Over Time | Earth.Org
Carbon dioxide now more than 50% higher than pre-industrial levels | National Oceanic and Atmospheric Administration
CO2 Levels: Current & Historic Atmospheric Carbon Dioxide / Global Temperature Graph & Widget
Carbon Dioxide Through Time | EARTH 103: Earth in the Future
CO2 on the atmosphere and annual emissions (1750-2019) | Real-World Economics Review Blog
FAQ: Is carbon dioxide harmful to the planet and the people? | Soletair Power
Carbon Dioxide Through Time | EARTH 103: Earth in the Future
10,000 Years of Carbon Dioxide - Berkeley Earth
CO2 Levels: Current & Historic Atmospheric Carbon Dioxide / Global Temperature Graph & Widget
Doesn't carbon dioxide in the atmosphere come from natural sources? | NOAA Climate.gov
A Graphical History of Atmospheric CO2 Levels Over Time | Earth.Org
Yearly Carbon Dioxide Peak
Why 350? - MN350
Graphic: The relentless rise of carbon dioxide – Climate Change: Vital Signs of the Planet
