( ( ( ( Carbon dioxide ) ( in ( ( atmosphere and ) carbon ) ) ) ( in ( the ( ocean 2.4.3 ) ) ) ) . )
(ROOT (NP (NP (NNP Carbon) (NN dioxide)) (PP (IN in) (NP (NN atmosphere) (CC and) (NN carbon))) (PP (IN in) (NP (DT the) (NN ocean) (CD 2.4.3))) (. .)))
Carbon dioxide in atmosphere and carbon in the ocean 2.4.3.
(ROOT (S (NP (NNP Ocean) (NNP acidification)) (VP (VBZ occurs) (SBAR (WHADVP (WRB when)) (S (NP (NP (JJ excess) (NN carbon) (NN dioxide)) (PP (IN in) (NP (DT the) (NN atmosphere)))) (VP (VBZ causes) (S (NP (DT the) (NNS oceans)) (VP (TO to) (VP (VB become) (NP (NNS acidic))))))))) (. .)))
Ocean acidification occurs when excess carbon dioxide in the atmosphere causes the oceans to become acidic.