Global Warming and Hurricanes - Essay Example

Farzeela Faisal Standard Academia Research Nov-20-2005 "How Global Warming and Hurricane are related" Global warming and Hurricane are interrelated in terms of climatic natural obsession as the strongest hurricanes in the present climate may be upstaged by even more intense hurricanes over the next century because the increasing levels of greenhouse gases in the atmosphere warms the earth's climate. Before getting into a detail I would like to discuss the few basics of global warming and Hurricanes in order to get a clear prospect. The world is undoubtedly warming and is getting humid with the passage of time which is the result of emissions of carbon dioxide and other greenhouse gases from human activities including industrial processes, fossil fuel combustion, and changes in land use, such as deforestation. Continuation of historical trends of greenhouse gas emissions will result in additional warming over the 21 century, with current projections of a global increase of 2.5F to 10.4F by 2100, with warming in the U.S. expected to be even higher. Hurricanes, tropical cyclones or typhoons, which can be defined as closed-circulation, warm-cored, low-pressure systems with maximum sustained surface wind speeds (1-minute mean) of at least 39 mph, are intense tropical storms with sustained winds above 74 miles/hour (Ahrens, C. Donald. Meteorology Today1) and are conventionally divided into two intensity classes: tropical storms (with maximum winds of 39-73 mph) and hurricanes (with maximum winds of at least 74 mph). Hurricanes have been subdivided into five potential damage classes depending on their maximum wind speed, minimum central pressure and storm surge magnitude. Sea level is rising and will continue to rise as oceans warm and glaciers melt. Rising sea levels means higher storm surges, even from relatively minor storms, causing coastal flooding and erosion and damaging coastal properties. In a distressing new development, scientific evidence now suggests a link between hurricane strength and duration and global warming. Understanding the relationship between hurricanes and global warming is essential if we are to preserve healthy and prosperous coastal communities. Storm intensity and duration increases as global warming emissions increase in our atmosphere. Rising sea levels, also caused in part by rising global temperatures, intensify storm damage along coasts. For hurricanes to occur, surface ocean temperatures must exceed or retain 80 degrees Fahrenheit. To understand how global warming can affect ocean storms, it's important to understand how these storms develop in the first place. Seasonal shifts in global wind patterns cause atmospheric disturbances in the tropics, leading to a local drop in pressure at sea level and forcing air to rise over warm ocean waters. As warm, moist air rises, it further lowers air pressure at sea level and draws surrounding air inward and upward in a rotating pattern called a vortex. When the water vapor-laden air rises to higher altitudes, it cools and releases heat as it condenses to rain. This cycle of evaporation and condensation brings the ocean's thermal energy into the vortex, powering the storm. Depending on the severity, meteorologists call these tropical storms or hurricanes in the Atlantic Ocean. Natural cycles alone cannot explain recent ocean warming. Because of human activities such as burning fossil fuels and clearing forests, today's carbon dioxide (CO2) levels in the atmosphere are significantly higher than at any time during the past 400,000 years. CO2 and other heat-trapping emissions act like insulation in the lower atmosphere, warming land and ocean surface temperatures. Oceans have absorbed most of this excess heat, raising sea temperatures by almost one degree Fahrenheit since 1970. September sea surface temperatures in the Atlantic over the past decade have risen far above levels documented since 1930. (Global Warming, Hurricanes and climate change) By examining the number of tropical cyclones and cyclone days as well as tropical cyclone, in an environment of increasing sea surface temperature, a large increase was seen in the number and proportion of hurricanes reaching categories 4 and 5. The largest increase occurred in the North Pacific, Indian, and Southwest Pacific Oceans, and the smallest percentage increase occurred in the North Atlantic Ocean. These increases have taken place while the number of cyclones and cyclone days has decreased in all basins except the North Atlantic during the past decade. Numerous studies have addressed the issue of changes in the global frequency and intensity of hurricanes in the warming world. Our basic conceptual understanding of hurricanes suggests that there could be a relationship between hurricane activity and Sea Surface Temperature (SST). It is well established that SST > 26C is a requirement for tropical cyclone formation in the current climate (J. Lighthill et al., Bull. Am, V W. M. Gray, Mon2) The increase in major storms like Katrina coincides with a global increase of sea surface temperatures, which scientists say is an effect of global warming and has made us suspicious of the possible relationship between global warming and hurricane strength. Using satellite data, the scientists link the increase in major storms to rising sea surface temperatures, which they believe have been influenced by global warming. However, the researchers will not go as far as to say that global warming is spinning up these larger storms. "We're not saying that global warming is causing there to be more intense hurricanes," study author Peter Webster of Georgia Tech told Live Science. "What we're saying is that sea surface temperatures are rising, and the intensity of hurricanes is associated with that. The warmer the sea surface temperature, the more intense the hurricanes." (3Increase in Major Hurricanes Linked to Warmer Seas By Bjorn Carey). As a hurricane builds up energy, it feeds off heat from the water. As water heats up, it turns into water vapor. As water vapor rises, it cools, condenses into rain, and releases heat that fuels the hurricane. The higher the vapor rises, the more heat is released, and the more intense the storm. From their data, Webster and his colleagues determined that global sea surface temperatures have increased by half a degree Celsius since 1970. As a result, waters worldwide are primed for making hurricanes. "Hurricane fuel, so to speak, is water vapor that rises from the surface. Small increases in sea surface temperature give you rapidly more vapor, making hurricanes more intense," Webster said. If natural variability is the cause of rising sea surface temperatures, different sea surface temperature patterns would occur in the different ocean basins because of variations in the atmosphere above them. However, Webster and his colleagues found fairly uniform temperature changes around the globe, leading them to believe this change is due to global warming. While warm water temperatures fuel hurricanes, a storm then cools down the sea surface. It is nature's way of moving energy from the tropics northward and dumping it, as rain, in places like the United States. "The only way you can supply energy is by cooling the surface. You take low energy water and make high-energy water vapor. In doing so, you cool the ocean surface," Webster said. "Hurricanes are very effective at taking energy out of the ocean." As the hurricane builds up, it pulls more and more water vapor away from the sea surface, releasing more heat as it does so. In addition to cooling the water this way, the intense hurricane winds also mix cool water from the deep with warmer surface water. Hurricanes are powered by the temperature difference between the top of the sea and the air above the storm, so warmer water was expected to pump the storms harder. But previous computer models had predicted that the half-degree increase in sea-surface temperatures from global warming over the past 30 years should have increased wind speed by only about 3 percent, corresponding to a 10 percent increase in Emanuel's estimate of destructive power. Instead, Emanuel found that the destructive power of North Atlantic storms more than doubled over the past 30 years. For northwest Pacific storms, the increase was about 75 percent. He attributes the sharp jump to increases in storm duration as well as much larger than expected increases in wind power. Two recent studies indicate that the effects of global warming on hurricanesare already happening. Meteorologist Kerry Emanuel of the Massachusetts Institute of Technology studied tropical storm and ocean temperature data and discovered that the destructive potential of tropical storms in the North Atlantic and Pacific has doubled over the past 30 years. At the Georgia Institute of Technology, researcher Peter Webster and colleagues found a sharp increase in the number of Category 4 and 5 hurricanes over the past 35 years. Emanuel and Webster's findings reinforce each other and suggest a strong link between global warming and more intense hurricanes. (4 Studies suggest global warming is making hurricanes stronger) At 5 a.m. EDT (0900 GMT) Tuesday, Wilma's center was located about 310 miles (500 kilometers) east of Cape Hatteras, North Carolina. The system was still a Category 3 storm with 115 mph (185 kph) winds, and was moving incredibly fast for a tropical system 53 mph (85 kph). It was expected to lose its tropical characteristics over cooler Atlantic waters late Tuesday or early Wednesday. Yet the United States may still get one last brush with Wilma. It was expected to link up with an area of low pressure already off the coast, raising fears about renewed flooding in areas in the northeast already hit hard by eight consecutive days of rain earlier this month. The remnants of Hurricane Wilma were expected to combine with two other storms to form a big storm called a nor easter that could bring high winds, heavy rains, coastal flooding and even snow in parts of southern New England on Tuesday. (5Northeast Braces for Wilma as Florida Cleans Up, By The Associated Press) On Monday August 29, Hurricane Katrina ravaged New Orleans, Louisiana and Mississippi, leaving a trail of destruction in her wake. It will be some time until the full toll of this hurricane can be assessed, but the devastating human and environmental impacts are already obvious. Katrina was the most feared of all meteorological events, a major hurricane-making landfall in a highly populated low-lying region. In the wake of this devastation, many have questioned whether global warming may have contributed to this disaster. Could New Orleans be the first major U.S. city ravaged by human-caused climate change Katrina storm was a weak hurricane when crossing Florida, and only gained force later over the warm waters of the Gulf of Mexico. More detailed analysis of the SST changes in the relevant regions, and comparisons with model predictions, will probably shed more light on this question in the future. At present, however, the available scientific evidence suggests that it would be premature to assert that the recent anomalous behavior can be attributed entirely to a natural cycle. Wilma was the most intense tropical cyclone ever recorded in the Atlantic basin and the tenth most intense globally, Wilma was the third Category 5 hurricane to develop in October, the other two being Hurricane Mitch of 1998 and Hurricane Hattie of 1961. Though the pressure of a hurricane is the best indicator of its strength since it can be precisely measured whereas winds have to be estimated, it is still important to note that it is actually the difference in the hurricane's pressure and that of its environment that actually gives it its strength. If two hurricanes have the same minimum pressure, but one is in an area of higher ambient pressure than the other, that one is in fact stronger. That hurricane had to work harder, so to speak, to get its pressure that low, and its larger pressure gradient would make its winds faster. For this reason, it is possible that in reality, Hurricane Wilma may not really be the strongest hurricane on record, despite having the lowest pressure ever. Hurricane Wilma existed within an area of ambient pressure that was unusually low to begin with. (6Hurricane Wilma) Better protection against hurricanes enables to suggest that: (a) Hurricanes tend to become more destructive as ocean temperatures rise, and (b) an unchecked rise in greenhouse gas concentrations will very likely increase ocean temperatures further, ultimately overwhelming any natural oscillations. End Notes Ahrens, C. Donald. Meteorology Today, Modelling the Effects of Global Warming on Hurricane Frequency and Intensity Using Remote Sensing Data 5th Ed.1994. West Publishing Company, St. Paul, Minnesota. Increase in Major Hurricanes Linked to Warmer Seas, By Bjorn Carey, Live Science Staff Writer posted: 15 September 2005, 02:01 pm ET J. Lighthill et al., Bull. Am. Meterol. Soc. 75, 2147 (1994), W. M. Gray, Mon. Weather Rev. 96, 669 (1968) Northeast Braces for Wilma as Florida Cleans Up, By The Associated Press, posted: 24 October 2005, 8:45 pm ET Studies suggest global warming is making hurricanes stronger, Hurricanes and Global Warming Is there a link Environmental Defense Weather, Climate Culture, Ben Orlove, Sarah Strauss, Berg. Place of Publication: New York. Publication Year: 2003. Page Number: 79. Works Cited Ahrens, C. Donald. Meteorology Today. 5th Ed. 1994. West Publishing Company, St. Paul, Minnesota. Increase in Major Hurricanes Linked to Warmer Seas, By Bjorn Carey, Live Science Staff Writer posted: 15 September 2005, 02:01 pm ET J. Lighthill et al., Bull. Am. Meterol. Soc. 75, 2147 (1994), W. M. Gray, Mon. Weather Rev. 96, 669 (1968) Northeast Braces for Wilma as Florida Cleans Up, By The Associated Press, posted: 24 October 2005, 8:45 pm ET Studies suggest global warming is making hurricanes stronger, Hurricanes and Global Warming Is there a link Environmental Defense Weather, Climate Culture, Ben Orlove, Sarah Strauss, Berg. Place of Publication: New York. Publication Year: 2003. Page Number: 79. Read More