(S (S (BASENP (DT This) (NN oil) (NN disaster)) (VP (MD may) (VP (VB be) (ADJP (ADJP (RB even) (JJR worse)) (PP (IN than) (NP (NP (BASENP (DT the) (NN one)) (PP (IN of) (BASENP (NNP February)))) (COMMA ,) (SBAR (WHNP (WDT which)) (S (VP (VBD was) (VP (VP (VBN described) (PP (IN by) (BASENP (DT the) (NNP BBC)))) (PP (IN as) (NP (BASENP (DT the) (JJS worst) (NN oil) (NN spill)) (SBAR (IN that) (S (BASENP (NNP Estonia)) (VP (VBZ has) (VP (ADVP (RB ever)) (VBN experienced))))))))))))))))) (PERIOD .))