CO2 in May 2020 at 417 ppm – highest in at least 2.5 million years

Despite the world grinding to a COVID-19 related halt in 2020, CO2 continues its inexhaustible rise.  Around this time of year the Mauna Loa CO2 record reaches its annual maximum and this year it is around 417 ppm (a 2 ppm increase on last year; see here).  As something of a tradition I have updated our plot of CO2 over the last 3.5 millions of years to reflect this. 

Plio-Pleistocene CO2 from ice core (red) and boron isotopes (blue). Sources indicated on text and listed here. Data downloadable here and Rscript here to make your own version of this figure.

While the CO2 rise we have seen thus far this year may well be a little bit smaller than expected because of the impact of COVID-19 (see this great analysis by Richard Betts and others for Carbon Brief here), it remains the case that atmospheric CO2 is higher NOW than it has been for around 2.5 million years.  As the economies of the world recover, CO2 will no doubt continue to increase in years to come.  Although Pliocene CO2 remains uncertain (watch this space!), with each passing year we are closer and closer to exceeding the CO2 levels last experienced 3 million years ago.