( ( Some ( air pollution ) ) ( ( is ( believed ( to ( have ( ( ( a ( direct effect ) ) ( on climate ) ) ( which ( is ( ( the ( primary cause ) ) ( of extinction ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT Some) (NN air) (NN pollution)) (VP (VBZ is) (VP (VBN believed) (S (VP (TO to) (VP (VB have) (NP (NP (DT a) (JJ direct) (NN effect)) (PP (IN on) (NP (NN climate))) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (NP (NP (DT the) (JJ primary) (NN cause)) (PP (IN of) (NP (NN extinction))))))))))))) (. .)))
Some air pollution is believed to have a direct effect on climate which is the primary cause of extinction.
(ROOT (S (NP (JJ Primary) (NNS pollutants)) (VP (VBP enter) (NP (DT the) (NN air)) (ADVP (RB directly))) (. .)))