How does global warming cause the climate to change?

Increases in average air and ocean temperatures destabilise climate systems and create extreme and unpredictable weather. In some regions this means heavier rainfall, which causes flooding (and often more erosion and subsequent desertification), whereas other areas experience longer droughts, heat waves and forest fires. When water gets warmer, it expands, which, along with the extra meltwater from disappearing ice caps, snow and glaciers, is causing sea levels to rise at the rate of several millimetres per year. The incidence of strong hurricanes (category 4 or 5) has nearly doubled in the past thirty years. Their relationship with global warming remains uncertain, although they have been linked to increased evaporation caused by rising tropical sea temperatures.