The number of tropical storms developing annually in the Atlantic Ocean more than doubled over the past century, with the increase taking place in two jumps, researchers say.

As the world warms, water -- either too little or too much of it -- is going to be the major problem for the United States, scientists and military experts said Monday. It will be a domestic problem, with states clashing over controls of rivers, and a national security problem as water shortages and floods worsen conflicts and terrorism elsewhere in the world, they said.

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.

Developing nations are least able to adapt to climate change. Despite being least responsible for emissions, these nations will be most affected by climate changes.