Global warming has many subtle influences on our atmosphere and our oceans.
As average global temperatures rise, icecaps and glaciers melt and the warmer ocean waters expand, all of which leads to rising sea levels. As the polar sea ice melts, the arctic waters reflect less heat back into space, warming the air overhead, and thus creating new wind patterns. Various other influences are also expected to change global wind patterns, with consequences that are often unpredictable.
Rising temperatures mean that there is more energy in the atmosphere, which can lead to more intense storms and higher storm surges. Droughts can become more severe and of longer duration because of the drying effect of higher temperatures. In other areas, the warmth can actually lead to more atmospheric moisture, which can result in more frequent sever floods.