( ( Rising ( ( ( CO 2 ) levels ) ( plus ( increases ( in ( greenhouse gases ) ) ) ) ) ) ( ( ( ( are ( due ( to ( human activity ) ) ) ) and ) ( ( cause ( a ( greenhouse effect ) ) ) ( that ( traps ( more heat ) ) ) ) ) . ) )
(ROOT (S (S (VP (VBG Rising) (NP (NP (QP (CD CO) (CD 2)) (NNS levels)) (PP (CC plus) (NP (NP (NNS increases)) (PP (IN in) (NP (NN greenhouse) (NNS gases)))))))) (VP (VP (VBP are) (ADJP (JJ due) (PP (TO to) (NP (JJ human) (NN activity))))) (CC and) (VP (VBP cause) (NP (DT a) (NN greenhouse) (NN effect)) (SBAR (IN that) (FRAG (NP (CD traps) (JJR more) (NN heat)))))) (. .)))
Rising CO 2 levels plus increases in greenhouse gases are due to human activity and cause a greenhouse effect that traps more heat.
(ROOT (S (NP (NNP Human) (NNS actions)) (VP (VBZ has) (VP (VBN increased) (NP (DT the) (NN greenhouse) (NN effect)))) (. .)))