( It ( ( ( is generally ) ( agreed ( that ( ( human activities ) ( have ( resulted ( in ( ( ( ( ( ( a ( significant increase ) ) ( in ( the production ) ) ) ( of ( these gases ) ) ) , ) ( producing ( an ( enhanced ( greenhouse effect ) ) ) ) ) ( which ( has ( become ( ( an issue ) ( of ( international concern ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (ADVP (RB generally)) (VP (VBN agreed) (SBAR (IN that) (S (NP (JJ human) (NNS activities)) (VP (VBP have) (VP (VBN resulted) (PP (IN in) (NP (NP (DT a) (JJ significant) (NN increase)) (PP (IN in) (NP (DT the) (NN production))) (PP (IN of) (NP (DT these) (NNS gases))) (, ,) (VP (VBG producing) (NP (DT an) (JJ enhanced) (NN greenhouse) (NN effect))) (SBAR (WHNP (WDT which)) (S (VP (VBZ has) (VP (VBN become) (NP (NP (DT an) (NN issue)) (PP (IN of) (NP (JJ international) (NN concern)))))))))))))))) (. .)))
It is generally agreed that human activities have resulted in a significant increase in the production of these gases, producing an enhanced greenhouse effect which has become an issue of international concern.
(ROOT (S (NP (NNP Human) (NNS actions)) (VP (VBZ has) (VP (VBN increased) (NP (DT the) (NN greenhouse) (NN effect)))) (. .)))