Congratulations, World! Atmospheric CO2 Levels Have Not Been This High in the Past Three Million Years

The world set a new record in May 2019, at least on a human perspective. Atmospheric concentrations of COreached 415.26 ppm on May 14, as recorded at the Mauna Loa Observatory in Hawaii, a level not seen in the past three million years.
To put that into perspective, the last time atmospheric concentrations of COwere this high, there were no humans on Earth. This was the Pliocene Epoch, where global temperatures were on average 2-3°C (3.6-5.8°F) higher than today; the oceans were up to 30 meters (90 feet) higher, the Himalayas were beginning to form, and forests covered parts of Antarctica. Not only did we set a “record” COconcentration this month, carbon dioxide emissions hit a record high in 2018, with the amount of increase of COin the atmosphere reaching the fourth highest on record. (Three of the four highest annual increases in atmospheric CO2concentrations have occurred in the past four years.) This is all occurring, of course, at the same time the IPCC is warning that net CO2 emissions globally must be reduced to zero by 2050 in order to keep the global temperature rise below 1.5°C. As hard as it would be to believe, if the world continues “business as usual,” atmospheric COconcentrations would reach 440 ppm by 2040, and approximately 500 ppm by 2050. That would put us back into the Eocene, right after the dinosaurs disappeared. We probably don’t want to go there.

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