<P> Concentrations of CO in the atmosphere were as high as 4,000 parts per million ( ppm ) during the Cambrian period about 500 million years ago to as low as 180 ppm during the Quaternary glaciation of the last two million years . Estimates based on reconstructed temperature records suggests that the amount of CO during the last 420 million years ago was with ~ 2000 ppm highest during the Devonian ( ∼ 400 Myrs ago ) and Triassic ( 220 -- 200 Myrs ago ) , with a few maximum estimates ranging up to ∼ 3,700 ± 1,600 ppm ( 215 Myrs ago ) . Global annual mean CO concentration has increased by more than 45 % since the start of the Industrial Revolution , from 280 ppm during the 10,000 years up to the mid-18th century to 410 ppm as of mid-2018 . The present concentration is the highest in the last 800,000 and possibly even the last 20 million years . The increase has been caused by human activities , particularly the burning of fossil fuels and deforestation . This increase of CO and other long - lived greenhouse gases in Earth 's atmosphere has produced the current episode of global warming . About 30 -- 40 % of the CO released by humans into the atmosphere dissolves into oceans , rivers and lakes , which has produced ocean acidification . </P>
<P> Concentrations of CO in the atmosphere were as high as 4,000 parts per million ( ppm ) during the Cambrian period about 500 million years ago to as low as 180 ppm during the Quaternary glaciation of the last two million years . Estimates based on reconstructed temperature records suggests that the amount of CO during the last 420 million years ago was with ~ 2000 ppm highest during the Devonian ( ∼ 400 Myrs ago ) and Triassic ( 220 -- 200 Myrs ago ) , with a few maximum estimates ranging up to ∼ 3,700 ± 1,600 ppm ( 215 Myrs ago ) . Global annual mean CO concentration has increased by more than 45 % since the start of the Industrial Revolution , from 280 ppm during the 10,000 years up to the mid-18th century to 410 ppm as of mid-2018 . The present concentration is the highest in the last 800,000 and possibly even the last 20 million years . The increase has been caused by human activities , particularly the burning of fossil fuels and deforestation . This increase of CO and other long - lived greenhouse gases in Earth 's atmosphere has produced the current episode of global warming . About 30 -- 40 % of the CO released by humans into the atmosphere dissolves into oceans , rivers and lakes , which has produced ocean acidification . </P>
what is the pre-industrial level of co2 on earth
what is the pre-industrial level of co2 on earth
280 ppm
280 ppm