the area where people lived under the iron boot of soviet communism was called east berlin. this film by the u.s. government helps to explain what it was like to live in postwar berlin. >> two and a half million people, more than half of berlin's population, lived in the american, british, and french zones. but the whole city was surrounded by the soviet zone of germany. supplying the two and a half million people of the western sectors was a system of rails, canals, and roads. >> but the soviets wanted berlin all to themselves. so, they set up a giant blockade, cutting off the roads and railroads to west berlin. >> the suspension of all traffic surface access to the city. the soviets claimed that technical difficulties caused the stoppage. the truth was that they were trying to force the western allies to surrender their position in berlin. and the weapon was hunger. >> with no food or supplies able to get in, the soviets expected the allies to pack up and leave. but they didn't. the united states and its allies refused to abandon the people to be starved into accepting sov

but for thousands of people's gulf and east coasts, those names are reminders of the incredibly destructive power of nature. emily tells us more.e in 2008, and sandy 2012. all were powerful hurricanes that slammed into the u.s. in recent years.n, and flooding caused tremendous damage. so, no wonder that the more we better.n expert on these super storms. he's a climate scientist at columbia university. welcome. >> thank you. it's good to be here.of a hurricane? a hurricane is a storm with very strong winds. it's a storm that forms over thepical oceans, and as soon as that storm's winds get up to about 35 miles an hour, we call it a tropical storm.t up to 75 miles an hour, it's a hurricane. >> how are hurricanes classified? >> hurricanes are classified by how strong their winds are.ricane, which is the weakest, has winds just above 75 miles an hour. category 5, which is the strongest, is winds at around >> so, what causes these hurricanes? >> hurricanes are caused by a combination of factors. several things have to comet a hurricane. is a warm ocean. hurricanes form over the warm with the war