( ( ( ( ( When ( ( ( the ( northern hemisphere ) ) ( of ( the Earth ) ) ) ( is ( tilted ( towards ( the Sun ) ) ) ) ) ) ( , ( ( the ( northern hemisphere ) ) ( gets ( more ( direct sunlight ) ) ) ) ) ) and ) ( they ( have summer ) ) ) . )
(ROOT (S (S (SBAR (WHADVP (WRB When)) (S (NP (NP (DT the) (JJ northern) (NN hemisphere)) (PP (IN of) (NP (DT the) (NN Earth)))) (VP (VBZ is) (VP (VBN tilted) (PP (IN towards) (NP (DT the) (NNP Sun))))))) (, ,) (NP (DT the) (JJ northern) (NN hemisphere)) (VP (VBZ gets) (NP (RBR more) (JJ direct) (NN sunlight)))) (CC and) (S (NP (PRP they)) (VP (VBP have) (NP (NN summer)))) (. .)))
When the northern hemisphere of the Earth is tilted towards the Sun, the northern hemisphere gets more direct sunlight and they have summer.
(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)))))))))))) (. .)))