( ( ( Greenhouse gases ) ( in ( the atmosphere ) ) ) ( ( have ( increased ( as ( ( a result ) ( of ( human activities ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Greenhouse) (NNS gases)) (PP (IN in) (NP (DT the) (NN atmosphere)))) (VP (VBP have) (VP (VBN increased) (PP (IN as) (NP (NP (DT a) (NN result)) (PP (IN of) (NP (JJ human) (NNS activities))))))) (. .)))
Greenhouse gases in the atmosphere have increased as a result of human activities.
(ROOT (S (NP (NNP Human) (NNS actions)) (VP (VBZ has) (VP (VBN increased) (NP (DT the) (NN greenhouse) (NN effect)))) (. .)))