We are concerned that the significant emissions reductions are required too quickly.
( We ( ( are ( concerned ( that ( ( the ( significant ( emissions reductions ) ) ) ( are ( required ( too quickly ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (VBP are) (ADJP (VBN concerned) (SBAR (IN that) (S (NP (DT the) (JJ significant) (NNS emissions) (NNS reductions)) (VP (VBP are) (VP (VBN required) (ADVP (RB too) (RB quickly)))))))) (. .)))
We're concerned about emissions reducing too quickly. 
( We ( ( 're ( concerned ( about ( emissions ( reducing ( too quickly ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (VBP 're) (ADJP (VBN concerned) (PP (IN about) (NP (NP (NNS emissions)) (VP (VBG reducing) (ADVP (RB too) (RB quickly))))))) (. .)))