Although the amount of atmospheric CO2 produced from fossil fuel is relatively well known, CO2 exchange between the biosphere and atmosphere from human activities on the land is highly uncertain.
(atmospheric CO2; produced; from fossil fuel) (the amount of atmospheric CO2; is; relatively well known) (the amount of atmospheric CO2; known; ) (CO2 exchange between the biosphere and atmosphere from human activities on the land; is; highly uncertain)
atmospheric CO2 the amount of atmospheric CO2 the amount of atmospheric CO2 CO2 exchange between the biosphere and atmosphere from human activities on the land
produced is known is
from fossil fuel
relatively well known
highly uncertain