( ( ( ( ( Fossil ( ( fuels and ) wood ) ) , ) ( when ( they ( are burned ) ) ) ) , ) ( ( ( release ( ( carbon dioxide ) ( -LRB- ( CO2 -RRB- ) ) ) ) ( into ( the atmosphere ) ) ) . ) )
(ROOT (S (NP (NP (JJ Fossil) (NNS fuels) (CC and) (NN wood)) (, ,) (SBAR (WHADVP (WRB when)) (S (NP (PRP they)) (VP (VBP are) (VP (VBN burned))))) (, ,)) (VP (VBP release) (NP (NP (NN carbon) (NN dioxide)) (PRN (-LRB- -LRB-) (NP (NNP CO2)) (-RRB- -RRB-))) (PP (IN into) (NP (DT the) (NN atmosphere)))) (. .)))
Fossil fuels and wood, when they are burned, release carbon dioxide (CO2) into the atmosphere.
(ROOT (S (NP (JJ Co2) (NN gas)) (VP (VBZ is) (VP (VBN released) (PP (IN into) (NP (NP (DT the) (NN atmosphere)) (SBAR (WHADVP (WRB when)) (S (NP (JJ fossil) (NNS fuels)) (VP (VBP are) (VP (VBN burned))))))))) (. .)))