During the past 50 years, sea levels have risen worldwide at an accelerating rate, believed to be partly due to the greenhouse effect. The burning of fossil fuels, cutting of forests, and other human activities are trapping more heat in the Earth's atmosphere. One result is an increased melting of glaciers and the polar ice caps, thus contributing to rising sea levels. The most dramatic changes in barrier islands are caused by storms, particularly hurricanes on the Gulf coast. The size, intensity, and speed of a storm, the tidal phase, and the storm's path influence overall impacts.
Severe erosion is more likely to occur if there are two or more high tide cycles during the storm.
Storm surge, an above-normal water level that results from low atmospheric pressure and high winds, can be especially damaging. Storms may also move sediments to the back dune by breaking through or over primary dunes. Generally, a storm flattens the beach and builds sandbars offshore. Natural forces usually rebuild the beach over time as wave action eventually pushes the sand ashore. This may take years.