This sucks in more warm air generating strong winds which shoots upwards. When this rush of air hits the stratosphere it flattens out and after getting influenced by earth’s rotation the storm starts turning counter clock wise. When the winds reach 39 mph it is considered a tropical storm. If there are aren’t any wind shears the storm’s air in the upper atmosphere will raise to higher and higher pressures resulting in hurricanes. So, Hurricanes are basically like giant engines that use warm, moist air as fuel.
The deadly winds caused by hurricanes result in a massive bulge of water called a storm surge by pushing down on the ocean surface. 90% of the casualties in hurricanes are due to the storm surge. Hurricanes have always bedevilled coasts, but global warming may be making matters worse. The most important parameter which determines hurricane intensity is sea surface temperature. Warmer water means more availability of warm, moist air thus incensing hurricane intensity. As heat from the ocean fuels the storm, an increasingly larger proportion of tropical storms are turning into hurricanes.
Sea level is rising and will continue to rise as oceans warm and glaciers melt. Rising sea level means higher storm surges, even from relatively minor storms, which increases coastal flooding and subsequent storm damage along coasts. Hurricane Katrina was the most devastating hurricane in recent history which ravaged through New Orleans in May 2005. Katrina was a weak (category 1) hurricane when crossing Florida, and only gained force later on encountering very warm water in the Gulf of Mexico.
The sea surface temperature in the Gulf of Mexico was high enough to provide enough heat and warm moist air to the storm to intensify it from category 1 to category 5. This unusually high sea surface temperature of the Gulf of Mexico can be attributed to global warming. New Orleans is bordered by Lake Pontchartrain which connects to the Gulf of Mexico. A network of canals and waterways run through the city which is connected to Lake Pontchartrain. All these water systems make New Orleans extremely vulnerable to devastation in case of a storm surge. To protect against flooding, levees were built around the cannels. But in case of hurricane Katrina, the storm surges were extremely high. Storm surge up to 15 feet high funnelled up the intercostal waterway and rushed into the industrial cannel. The levee around the canal was overtopped and the levee later scurried away due to the force of the water. These resulted in the drowning of a large number of working class suburbs around New Orleans. When Katrina hit Gulf Port and St Louis, the storm surge was up to 28 feet high. Houses and cars were swapped away.
Thus, the casualties in this hurricane could have been a lot less if the water level was lower. Lower water levels would have meant a much lower storm surge. Therefore, the large devastation caused by Katrina can be blamed to rising sea levels which is a direct impact of global warming. In fact a large proportion of the devastation occurred because of the flooding of the densely populated working class areas caused by the overtopping of the levees around the industrial canal. This reason for this overtopping was solely the high water levels due to global warming.
Marshlands due to silt deposition from the Mississippi used to cover a major portion of New Orleans. This marshlands used to protect New Orleans from flooding by acting as a sponge and sucking the water in. Some of the marsh lands were dried using pumps so that the city could grow. But now, vast areas of this marsh lands are drying every hour. This drying might be partly due to increase rate of evaporation due to increased temperatures due to global warming. If there was a larger area of marshland, the intensity of the floods due to storm surge from Hurricane Katrina would have been a lot lower.
There is observational evidence for an increase of intense tropical cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface temperatures. Based on a range of models, it is likely that future tropical cyclones will become more intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of tropical Sea surface temperatures. An increasingly larger proportion of hurricanes will be category 4 or 5. Therefore, precautions must be taken to encounter stronger winds and much higher storm surges.
In New Orleans, the levees were only capable to withstand category 3 Hurricanes. Stronger levees must be built which would be able to withstand category 5 conditions. Also the levees must be made higher considering the increasing water levels so that they don’t get easily overtopped. Devastation by Hurricane Katrina should be taken as a strong warning of the adverse effects of climate change. It is very likely that the human-induced increase in greenhouse gases has contributed to the increase in sea surface temperatures in the hurricane formation regions.
So measures should be taken to control greenhouse gas emissions. If no action is taken to encounter this issue, more and more intense hurricanes are going to devastate the coast frequently.
- Storm that Drowned a City- A documentary aired in November 22, 2005 on PBS
- http://en. wikipedia. org/wiki/Hurricane_Katrina_and_global_warming
- http://abcnews. go. com/Technology/DyeHard/story? id=1121948&page=1#. UFE20I3iZEM
- http://all4energy. org/news/did-global-warming-cause-katrina-levee-breaks