[问答题]
1.Describe the method used by scientists to de 451(mdoo08ihl( dsmzxtf t w)ducoq9y4ad r p3ots : eh+znsb8*4 gqrn1;e carbon dioxide concentrations from thousr94*odqt+qps:4hnby 8e;rz3ogsan 1 ands of years ago.
2.Explain why rising levels of atmospheric carbon dioxide are the main cause of climate change.
3.How have increased carbon dioxide levels affected reef-building corals in marine waters?
