During the winter of 2009-2010 the United States experienced extreme weather conditions. There were record setting blizzards in the Mid-Atlantic States. At one time 49 of 50 states had snow and this snow covered two-thirds of the nation’s land mass. This led some people to speculate that these weather conditions contradict the global warming hypothesis. Others argue that global warming predicts the occurrence of these extreme weather patterns. The answer to this paradox lies in the water!
Water can absorb and store significant amounts of heat without raising its temperature. This is referred to as high heat capacity. Anyone who has walked on a beach on a hot summer day knows about the heat capacity of water. On a hot day the beach sand is too hot to stand on but the ocean water is cool. Sand has a much lower heat capacity than water. This high heat capacity allows water to store heat which is transported by ocean currents to increase the temperature of colder parts of the planet. The warm water of the Gulf Stream, for example, creates a mild maritime climate for England and Ireland. However, as the temperature of ocean water continues to rise it must release heat in the form of water vapor. As the water vapor rises in the atmosphere it cools by releasing heat to outer space. This cooling triggers the formation of clouds. These clouds continue to release heat and eventually form precipitation as rain, snow or hail. Since the oceans cover about 71% of the Earth’s surface, it is easy to comprehend how increasing temperature associated with global warming could stimulate an increase in water vapor/precipitation and thus contribute to the extreme weather seen during the winter of 2009-2010.
El Niño is an example of how a local increase in ocean water temperature can help create extreme weather throughout the planet. Under normal conditions the trade winds transport cold water off the western coast of South America to the warm water of the Western Pacific which contains the warmest water found in all oceans. For reasons still unknown to scientists the trade winds can weaken, stall and reverse course. This change in wind direction is called El Niño or Southern Oscillation. This change in wind direction transports warm Western Pacific water to the west coast of South America. This warm water triggers extreme weather conditions over much of the Pacific and parts of the Atlantic and Indian Oceans. The El Niño during the winter of 1997-1998 produced heavy rains in the Eastern Pacific that left at least 250,000 people homeless and closed all sea ports in Peru for at least a month. Rainfall in California exceeded twice the normal amount producing mud slides and avalanches. Hawaii experienced record drought and some parts of southwestern Africa and New Guinea received so little rain that crops failed completely and whole villages were abandoned due to starvation. The Indian Ocean lost more than 90% of its coral due to increasing ocean temperature.
The extreme weather conditions during the winter of 2009-2010 do not disprove the global warming hypothesis. Global warming does predict extreme weather and weather patterns created by El Niño support this hypothesis. However, the affect of ocean water on global climate is a complex issue requiring more research.