( ( Because ( CO2 ( ( ( absorbs ( energy ( emitted ( from ( the Earth ) ) ) ) ) and ) ( ( prevents it ) ( from ( ( going ( back out ) ) ( into space ) ) ) ) ) ) ) ( , ( it ( ( is ( called ( a ( greenhouse gas ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN Because) (S (NP (NNP CO2)) (VP (VP (VBZ absorbs) (NP (NP (NN energy)) (VP (VBN emitted) (PP (IN from) (NP (DT the) (NN Earth)))))) (CC and) (VP (VBZ prevents) (NP (PRP it)) (PP (IN from) (S (VP (VBG going) (ADVP (RB back) (RB out)) (PP (IN into) (NP (NN space)))))))))) (, ,) (NP (PRP it)) (VP (VBZ is) (VP (VBN called) (NP (DT a) (NN greenhouse) (NN gas)))) (. .)))
Because CO2 absorbs energy emitted from the Earth and prevents it from going back out into space, it is called a greenhouse gas.
(ROOT (S (NP (NP (NNS Gases)) (PP (JJ such) (IN as) (NP (NN co2) (CC and) (NN methane)))) (VP (MD can) (VP (NN trap) (NP (NP (JJ thermal) (NN energy)) (PP (IN in) (NP (NP (NN earth) (POS 's)) (NN atmosphere)))) (PP (IN before) (S (VP (VBG radiating) (NP (PRP it)) (PP (IN into) (NP (NN space)))))))) (. .)))