( This ( ( is ( ( the start ) ( of ( summer ( in ( ( the ( northern ( ( hemisphere and ) winter ) ) ) ( in ( the ( southern hemisphere ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (NP (NP (DT the) (NN start)) (PP (IN of) (NP (NP (NN summer)) (PP (IN in) (NP (NP (DT the) (JJ northern) (NN hemisphere) (CC and) (NN winter)) (PP (IN in) (NP (DT the) (JJ southern) (NN hemisphere))))))))) (. .)))
This is the start of summer in the northern hemisphere and winter in the southern hemisphere.
(ROOT (S (NP (NP (DT The) (NN tilt)) (PP (IN of) (NP (NP (NN earth)) (PP (IN on) (NP (PRP$ its) (NNS axis)))))) (VP (VBZ causes) (NP (NN summer)) (S (VP (TO to) (VP (VB be) (VP (VBN warmer) (PP (IN than) (NP (NP (NN winter)) (PP (IN in) (NP (DT the) (JJ northern) (NN hemisphere))))) (SBAR (IN because) (S (NP (NP (DT the) (NNS rays)) (PP (IN of) (NP (DT the) (NN sun)))) (VP (VBP strike) (NP (DT the) (JJ northern) (NN hemisphere)) (ADVP (ADVP (RBR more) (RB directly)) (PP (IN in) (NP (DT the) (NN summer)))))))))))) (. .)))