(S (S (S (NP (BASENP (NN Change)) (PP (IN in) (BASENP (NN cloudiness) (CC and) (NN weather)))) (VP (MD could) (VP (VB have) (VP (ADVP (RB also)) (VP (VP (VP (VBN been) (BASENP (NNS factors))) (PP (IN in) (NP (BASENP (DT the) (NN retreat)) (PP (IN of) (BASENP (DT the) (NN ice)))))) (COMMA ,) (PP (ADVP (RB especially)) (PP (IN in) (BASENP (JJ recent) (NNS decades))))))))) (COMMA ,) (S (BASENP (NNS scientists)) (VP (VBD said)))) (PERIOD .))