Hurricane Sandy a category 3 storm, hit the Caribbean and mid-alantic and Northeastern United States during late October 2012. The storm estimated to have caused nearly $75 Billion (2012 USD) making it the second costliest hurricane. 285 people were killed along the storm in seven counties. When the sea level rises, because of global warming it causes the storm to be more destructive. Boston, NYC, and Norfolk are all places that increase four times faster than the global average. Human activities also contribute, they increase sea surface temps which increase the water vapor. This leads to more rainfall which means a much higher chance of flooding. Climate scientists have warned NYC before that climate change was dramatically increasing the odds of stronger storms.
These factors definitely contributed to Sandy being more destructive then planned but was not the main cause. Sandy fed off of unusually warm water temps in the Atlantic ocean and a high-pressure system that forced the storm to remain inland rather than cast out to sea. The winter storm coming in from the west only added to the issue making the storm disastrous.
Sources:
http://en.wikipedia.org/wiki/Hurricane_Sandy
http://www.scientificamerican.com/article.cfm?id=hurricane-sandy-spins-up-climate-discussion
http://crooksandliars.com/susie-madrak/how-global-warming-made-hurricane-san