( Likewise ( , ( ( human activities ) ( ( appear ( to ( have ( ( increased ( ( the amount ) ( of ( greenhouse gases ) ) ) ) ( in ( the atmosphere ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Likewise)) (, ,) (NP (JJ human) (NNS activities)) (VP (VBP appear) (S (VP (TO to) (VP (VB have) (VP (VBN increased) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN greenhouse) (NNS gases)))) (PP (IN in) (NP (DT the) (NN atmosphere)))))))) (. .)))
Likewise, human activities appear to have increased the amount of greenhouse gases in the atmosphere.
(ROOT (S (NP (NNP Human) (NNS actions)) (VP (VBZ has) (VP (VBN increased) (NP (DT the) (NN greenhouse) (NN effect)))) (. .)))