This article discusses the last time that there was as much CO2 in the atmosphere as there is today.
The last time atmospheric carbon dioxide levels were this high, millions of years ago, the planet was very different. For one, humans didn’t exist.
On Wednesday, scientists at the University of California in San Diego confirmedthat April’s monthly average atmospheric carbon dioxide concentration breached 410 parts per million for the first time in our history.
We know a lot about how to track these changes. The Earth’s carbon dioxide levels peak around this time every year for a pretty straightforward reason. There’s more landmass in the northern hemisphere, and plants grow in a seasonal cycle. During the summer, they suck down CO2, during the winter, they let it back out. The measurements were made at Mauna Loa, Hawaii — a site chosen for its pristine location far away from the polluting influence of a major city.