( ( When burned ) ( , ( ( coal ( , ( oil ( and ( natural gas ) ) ) ) ) ( ( ( release ( their ( carbon dioxide ) ) ) ( into ( ( ( the atmosphere ) , ) ( helping ( to ( raise ( ( the ( earth 's ) ) ( average temperature ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (VP (JJ burned)))) (, ,) (NP (NN coal) (, ,) (NN oil) (CC and) (JJ natural) (NN gas)) (VP (VBP release) (NP (PRP$ their) (NN carbon) (NN dioxide)) (PP (IN into) (NP (NP (DT the) (NN atmosphere)) (, ,) (VP (VBG helping) (S (VP (TO to) (VP (VB raise) (NP (NP (DT the) (NN earth) (POS 's)) (JJ average) (NN temperature))))))))) (. .)))
When burned, coal, oil and natural gas release their carbon dioxide into the atmosphere, helping to raise the earth's average temperature.
(ROOT (S (NP (JJ Volcanic) (NNS gases)) (VP (VBP helpe) (S (VP (TO to) (VP (VB form) (NP (DT the) (NN atmosphere)) (PP (IN on) (NP (NN earth))))))) (. .)))