( ( On Thursday ) ( , ( Bush ( ( ( called ( natural gas ) ) ( ( a ( clean ( energy source ) ) ) ( that ( could ( help ( reduce ( greenhouse ( gas emissions ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN On) (NP (NNP Thursday))) (, ,) (NP (NNP Bush)) (VP (VBD called) (NP (JJ natural) (NN gas)) (NP (NP (DT a) (JJ clean) (NN energy) (NN source)) (SBAR (WHNP (WDT that)) (S (VP (MD could) (VP (VB help) (VP (VB reduce) (NP (NN greenhouse) (NN gas) (NNS emissions))))))))) (. .)))
On Thursday, Bush called natural gas a clean energy source that could help reduce greenhouse gas emissions.
(ROOT (S (NP (JJ Geothermal) (NN energy) (NN energy)) (VP (VP (VBZ is) (ADJP (JJ clean))) (CC and) (VP (VBZ does) (RB not) (VP (VB release) (NP (NN greenhouse) (NNS gases))))) (. .)))