from kerry emanuel theory of thermodynamics we can work out the maximum potential and from statistics we can work out out, we have two different intensities. let me try to put this together. have limiting intensities indicated by this red line here. we take our hurricanes of the last set of years and we can look at how strong they got. this is how fast they are rotating in meters per second. then we can just plot them and you can see these black dots represent that curve. notice what happens to those black dots. they start to flatten out. at some level you can't get a stronger hurricane. that level here for this set of storms as right at 75 meters per second. that's what i mean by limiting intensity. that is a brilliant statistical theory. it tells us about what is the maximum you can get given the set of values you have. think about that. think about it. if i take 30 people in this room might now if i measured the , height of every one of you and then ranked them from shortest to tallest, i would have a single tall person in this room but i would not say that is the tallest person th

. >> o'brien: kerry emanuel is a professor of atmospheric science at the massachusetts institute of technology we have a lot of extreme weather events. whether or not the climate changes to attribute a particular event to climate change is next to impossible. >> because, for those really rare events, it's hard to even know how common they are, before you get to climate change. >> o'brien: radley horton is a climate scientist at columbia university's lamont doherty earth observatory. >> you probably want to have 500 years of data, a thousand years of data, to estimate those statistics. and of course, we don't have data records to go back 500 years or a thousand years. >> i'm very uncomfortable talking about causation of one particular storm, in the same way that i can't identify what particular home run was hit by a baseball player because of steroid use. >> o'brien: marshall shepherd is a professor of geography and atmospheric sciences at the university of georgia. >> i think that we know that steroid use likely increases the probability or chance that there will be more home runs in baseball.

about 150 people died, putting it in the top 25 most fatal hurricanes.mit meteorology professor kerry emanuel says indianola was a thriving city before it was struck and it never came back. according to texas escapes magazine, it's now pretty much a ghost town.emanuel says that harvey "is going around the same place."more than 15,000 people aboard three carnival cruise line ships scheduled to return to galveston, texas, this weekend face delays or detours due to hurricane harvey in the gulf of mexico. the port of galveston was closed friday amid the hurricane threat.a statement friday from the miami-based cruise line says the carnival freedom and carnival valor were at sea and would remain a safe distance from the hurricane. both ships were originally scheduled to dock in galveston on saturday but will instead stop replenish supplies.the carnival carnival valor each carry about 4,800 passengers statement says they'll resume their return to soon as possible.the carnival scheduled to return to galveston on spending friday night in cozumel, mexico. that ship 6,000 on board. the carnival statemen