( ( The ( enhanced ( greenhouse effect ) ) ) ( ( refers ( to ( ( the effect ) ( caused ( by ( ( increased amounts ) ( of ( ( greenhouse gases ) ( from ( human activities ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ enhanced) (NN greenhouse) (NN effect)) (VP (VBZ refers) (PP (TO to) (NP (NP (DT the) (NN effect)) (VP (VBN caused) (PP (IN by) (NP (NP (VBN increased) (NNS amounts)) (PP (IN of) (NP (NP (NN greenhouse) (NNS gases)) (PP (IN from) (NP (JJ human) (NNS activities))))))))))) (. .)))
The enhanced greenhouse effect refers to the effect caused by increased amounts of greenhouse gases from human activities.
(ROOT (S (NP (NNP Human) (NNS actions)) (VP (VBZ has) (VP (VBN increased) (NP (DT the) (NN greenhouse) (NN effect)))) (. .)))