( ( Human activities ) ( ( ( have already ) ( caused ( ( the amount ) ( of ( ( carbon ( dioxide equivalent ) ) ( in ( the ( atmosphere ( to ( increase ( by ( ( ( as ( much ( as 50 ) ) ) % ) ( since ( preindustrial times ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Human) (NNS activities)) (VP (VBP have) (ADVP (RB already)) (VP (VBN caused) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN carbon) (NN dioxide) (NN equivalent)) (PP (IN in) (NP (DT the) (NN atmosphere) (S (VP (TO to) (VP (VB increase) (PP (IN by) (NP (NP (QP (RB as) (JJ much) (IN as) (CD 50)) (NN %)) (PP (IN since) (NP (JJ preindustrial) (NNS times))))))))))))))) (. .)))
Human activities have already caused the amount of carbon dioxide equivalent in the atmosphere to increase by as much as 50% since preindustrial times.
(ROOT (S (PP (IN During) (NP (DT the) (JJ early) (NN paleozoic))) (, ,) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN carbon) (NN dioxide)) (PP (IN in) (NP (DT the) (NN atmosphere)))))) (VP (VBD was) (ADJP (RB much) (JJR greater)) (PP (VBN compared) (PP (TO to) (NP (NN today))))) (. .)))