( Humans ( ( are ( ( the ( primary cause ) ) ( of ( ( global warming ) ( since 1950s ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Humans)) (VP (VBP are) (NP (NP (DT the) (JJ primary) (NN cause)) (PP (IN of) (NP (NP (JJ global) (NN warming)) (PP (IN since) (NP (CD 1950s))))))) (. .)))
Humans are the primary cause of global warming since 1950s.
(ROOT (S (NP (NNP Human) (NNS beings)) (VP (VBP is/are) (NP (NP (DT the) (JJ main) (NN cause)) (PP (IN of) (NP (JJ recent) (JJ global) (NN warming))))) (. .)))
Human beings is/are the main cause of recent global warming.