In the past, hurricane activity has been somewhat predictable, at least on a grand scale. We could be reasonably sure that hurricanes would form in either the North Atlantic or the Gulf of Mexico, and would either rotate north and then east to die in colder waters, or strike the US, some of the Caribbean islands, or maybe Mexico. In recent years, however, there has been some erratic activity:

In 2004 Cyclone Cata-rina became one of the very few ever to form in the South Atlantic, hitting the coast of Brazil. Then, in 2005 Hurricane Vince formed around Madeira, an area that had never before produced such storms. It even struck Spain – another first. The same year also saw New Orleans overwhelmed by Hurricane Katrina and the American Gulf coast hit by Hurricane Rita, the fourth-most intense Atlantic hurricane ever recorded. Hurricane researchers were shocked and have since put huge efforts into predicting how future climate change might alter patterns of hurricane formation. - Times Online

In fact, a new study, conducted by climate scientists in Spain, has concluded that we can expect more changes in cyclonic activity, including the possibility of hurricanes forming in the Mediterranean Sea:

Global warming could trigger hurricanes, or tropical cyclones, over the Mediterranean sea, threatening one of the world's most densely populated coastal regions, according to European scientists. Hurricanes currently form out in the tropical Atlantic and rarely reach Europe, but a new study shows a 3 degrees Celsius (5.4 degrees Fahrenheit) rise in average temperatures could set them off in the enclosed Mediterranean in future. "This is the first study to detect this possibility," lead researcher Miguel Angel Gaertner of the University of Castilla-La Mancha in Toledo, Spain, told Reuters on Monday. "Most models in our study show increasing storm intensity and if you combine this with rising sea levels, as are projected, this could be damaging for many coastal settlements." - Reuters

I think many people are not aware of the many ways in which climate change can affect our lives and the lives of those that will inhabit this planet in the future. I've heard some skeptics say things like, "so we'll warm a couple of degrees, big deal", as if the only concern is warmer weather. This is an extremely myopic view, which demonstrates a failure to understand the true effects of global warming. These effects include drought, severe weather, famine, and even war, among other things. For more information, an excellent source is the recent report (PDF) by the IPCC's Working Group II.

Hurricane Katrina footage, from inside the Beau Rivage Duration: 10 mins