yvonne maldonado, thank you so much for being here. >> it's a pleasure.. >> woodruff: despite world leaders from more than 100 countries being in attendance at the u.n. climate conference, one significant figure is absent: china's xi jinping, president of the globe's largest polluter. without china, efforts to fight climate change will likely be in vain. and, reducing china's reliance on coal is key. we've now got two looks. in a moment, we'll hear from special correspondent patrick fox in northern china. but first, here's nick schifrin. >> schifrin: in china, it is the best of times... and it is the worst of times. beijing produces more solar power, more wind power, and more electric cars than any country in the world. but china also produces more greenhouse gases than the rest of the industrialized world combined. >> there's schizophrenia there-- that there is both an investment in the future, in exactly the kind of technologies that are going to be needed to build a sustainable economic engine for their country; at the same time, clinging to some of th

yvonne maldonado, professor of infectious diseases at stanford about what we know so far about the omicron. what's your biggest concern about the omicron variant right now? >> the concern -- the biggest concern is whether or not the antibodies that we've developed from the vaccination will actually protect us from the omicron virus, and we just don't know the answer to that yet. >> and, dr. maldonado, you talked about the vaccines, but how effective are the tests we currently have at detecting this variant? >> the tests apparently are excellent, so we've already heard from three major companies that they've already provided results showing that their tests work really well in picking up the omicron variant. so that's good news. >> and, dr. maldonado, do you think the travel restrictions put in place by certain countries is a little preemptive right now? >> well, i think we are just so scared right now. we thought we had this delta under control, and it's so hard to know exactly what this virus is going to do, but i think in the next couple of weeks we'll have a better idea, so it's hard to