one demographer, joel cohen, from rockefeller university, a few years ago, looked at all the estimates made of population size and sustainability -- trying to answer the question, "how many are too many?" and it really came down to a huge array of estimates and depended on what kind of life you wanted. and that's what really goes into this equation. it's a matter of trade-offs. narrator: while farnsworth riche's research is based mainly in the united states, deborah balk's studies have a predominantly global perspective. with 6.5 billion people currently living on the planet, it's estimated that world population mapeak at around 9.1 billion in the next 50 yrs. scientists predict that climate change linked to greenhouse-gas emissions will lead to changes in the global environment, including a rise in ocean levels. in developing nations, the majority of population growth is projected to take place in cities. many of these cities are situated in low-lying coastal areas -- eas most at risk for climate-change effects. balk: we know climate change will lead to sea-level rise, and that, of co

rockefeller christmas tree in person when we get started right here on "today." >> that's exciting. >> we'll see up then. >>> happening today, jury unarmed black man near the university of cincinnati. on friday the panel told the judge they could not reach a decision on murder or voluntary manslaughter charges. she ordered them back to work. she told the jors they had all the information to make a verdict. >>> two teenagers are in custody. a 17-year-old from ashburn was 16-year-old from virginia also facing charges. last friday night two men were stabbed near an apartment complex. one man died and another was hurt. the victims appear to have been targeted. >>> residents in peru have been evacuated after explosions that evacuation. the eruption shot more than 4,900 feet in the area. thousands of residents forced out. southern peru is home to more than one dozen volcanos. >>> counties in tennessee have wildfires burning this morning when trees behind a home caught fire on friday neighbors and policed to work together to keep firefighters arrived. one homeowner used a rake and garden hose. >>> if you're an amazon customer you might be owed money back. >> reporter: the c

rockefeller center. joining us now, nbc news special correspondent tom brokaw and chair of african-american studies at princeton university and columnist for "time" magazine eddie glaude jr. and harold ford jr. back with us. >> tom, people said trump didn't have a path and we reminded them yesterday morning when someone was talking about historic significance about how tonight we were electing the first woman president, i said tom brokaw basically took a cold shoulder back in 2008 when everybody said that hillary clinton was going to get crushed in new hampshire and said let's wait for the people to vote. same thing happened over the past month. nobody wanted to wait to hear what the people had to say. >> you know, as you know i also say ufo theory. unforeseeable will occur. i'll put it in a hall of fame all of its own. like everyone else, i was beginning to buy into the idea that she was going to win this. yesterday morning. stop and think about this. organizations like this around the country were talking about how can the republican party possibly repair ielf after this election? they're going to lose the presidency. t

university with mr. barlow. these model conventions were no simple class simulations. major presidential candidates came by and spoke to the crowd of student delegates. robert ken dirks nelson rockefeller, george mcgovern, hubert humry, jimmy carter, ronald reagan, george h.w. bush, michael dukakis, and bill clinton all stopped by at a model convention as they campaigned ahead of oregon's presidential primaries. . but former students know that his -- he also connected with and motivated his students in smaller, quieter ways as well. his psychology, philosophy and current affairs courses were legendary at the high school where he spent most of his career. he challenged them to think critically. he encouraged them to consider new perspectives on information they consume. and as a teacher he saw potential in every student. with his dry wit, his deep knowledge and genuine enthusiasm for his subject matter, mr. bar low created a learning -- mr. barlow created a learning atmosphere where everyone felt and everyone was welcomed and valuable. there was mg that helped with the welcoming -- there was something that helped with the welcoming, doughnuts. long before doughnuts were a craze in portl