Architect and writer, Director of the REAL foundation and Editor-in-Chief of Real Review
The 2021 average parts per million (ppm) of atmospheric carbon dioxide is 415. That is 15% higher than just 25 years ago (361ppm in 1996). This is the difference between what used to be called "fresh air" and "indoor air". There is no more fresh air. The whole planet has come indoors. This rising ppm is also a reversal of time: the atmospheric CO2 ppm is the same today as 4 million years ago.