tina krause is in london with the details. >> reporter: good morning. it's not easy to getetearly 200 countries to agree on anything, especially something with such an economic impact. the summit opens this morning and it's expected to last for two weeks. negotiators will try to come to terms on a deal that will slow and reduce greenhouse gas emissions. and at least slow down the effect of global warming. president obama will be in paris two days. he arrived last night and went directly to the concert hall, the bataclan, where the most people were killed during the terrorist attacks two weeks ago. also last night, protesters clashed with police. french forces used tear gas to stop demonstrators who defied a government ban on protests. french authorities did not want large crowds gathering after the terrorist attacks. this is the kind of pollution smog in shanghai reached hazardous levets this morning and two previous summits did nothing on change the way developing economies like china and india operate. that is the biggest stumbling blocks. developing

. >> tina krause in london, thank you very much. >>> london donald trump is not backing down and says he was 100% right when he saw muslims in new jersey celebrating the 9/11 attacks. >> i saw so many people saw it, chuck. so why would i take it back? i'm not going to take it back. >> trump has come under fire for his remarks. there is no evidence that large numbers of muslims in new jersey celebrated the world trade center attacks. fellow represent presidential candidate jeb bush says he has grave doubts about trump's ability to be commander in chief. >> if you listen to him talk, it's -- it's -- it's kind of scary, to be honest with you, because he is not a serious candidate. >> bush says he is confident the more people hear from trump, the less likely trump will get the gop nomination. coming up on "cbs this morning" we will discuss the trump campaign with john dickerson. >>> enhanced surveillance video that shows a cleveland police officer fatally shooting 12-year-old tamir rice has been released. the video will be presented to a grand jury that is deciding whether to indict the o