Nightly News | October 30, 2012
>>> the storm had the lowest low pressure ever recorded in the hemisphere. a storm like this has a way of making you ask questions like, what's happening to our world and our weather? and, yes, people are raising global warming already. our report tonight from our chief foreign correspondent robert bazell .
>> reporter: another storm of the century . a bit more than a year after the last one in the same place. most scientists have no doubt of the overall cause.
>> we have a new normal, really. it's the background environment for all weather systems has changed.
>> reporter: even some politicians agree.
>> anyone who says there's not a dramatic change in weather patterns, i think is denying reality.
>> reporter: everyone agrees that no single weather event can be attributed to the warming of the atmosphere, from human produced carbon dioxide . but many say it plays a big role.
>> human beings don't make hurricanes but long term climate change can certainly interact with hurricanes and in some cases make them worse.
>> reporter: increasing carbon dioxide warms the air. the major effect is in the oceans.
>> the oceans are warmer than they used to be. not just at the surface, but below the surface.
>> reporter: hurricanes get their energy from warm oceans making them potentially more powerful. warmer oceans mean rising sea levels . the sea levels are higher now than they were a few decades ago. that means that every storm has a greater chance of washing over the levees just as sandy did. global warming by changing weather patterns also contributes to more intense droughts and wildfires as well. it will take decades to change. the new normal is likely to get worse before it gets better. robert bazell , nbc news, new york.