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How is Global Warming Effecting Hurricanes

Introduction

As we all know oceans cover about 70% of the Earth’s surface and typically the principle component of hydrosphere and contain roughly 97% of the Earth’s water supply. It plays very important role in the Earth’s climate by transferring warm as well as cold air and precipitation to coastal regions, where they may be carried inland by winds. The winds give energy to the sea surface that result in ocean currents. The currents carry heat from one location to another, changing the Earth’s surface temperature patterns and bring in changes in the atmosphere. Hence, ocean has a tremendous affect on climates and visa-versa.

The thermohaline circulation of the ocean distributes heat energy between the equatorial and Polar Regions of the earth while other ocean currents do the same between land and water. However, today with the increase in the emissions of greenhouse gases, scientists and environmentalists are equally concerned that the polar ice caps could probably melt and contribute to the increase in ocean level. In recent years global warming is linked by many to the strength and number of hurricane. This is a research paper on a “CASE ANALYSIS” of a crisis we are facing with global warming and how it is affecting hurricanes.

There are several studies that show that in the past years temperature has risen on the globe including the ocean temperature. Incidentally, during these years the number of hurricanes has also risen. This is the basic reason that scientists began to think if the increase in temperature is causing the disaster of hurricanes which need warm water to thrive. A few scientists also think that the temperature increase could also cause a “super-hurricanes” or the ultimate hurricanes in the U.S. east coast shores. It is predicted that these hurricanes will be more powerful than the once experienced till now (personal.psu.edu, N.D.). Before we get into the details of how global warming can result in stronger and increasing number of hurricanes, it is important to understand what is global warming.

Global Warming

Global Warming as the word suggest is an increase of the global average temperature and is also termed as Greenhouse Effect. In general, the greenhouse gases include water vapor, carbon dioxide, methane and nitrous oxides which are responsible to trap heat that has been reflected from the earth’s surface. Scientific studies provide enough proof that on an average, the global temperature has increased 0.5°C over the last 100 years. However, there was a rapid increase in temperature only in the past 10-15 years and has resulted in climate changes (personal.psu.edu, N.D.).

The sea interacts with the atmosphere in two different methods, physically and chemically. The physical way is through the exchange of heat, water, and momentum. More than 70 percent of the Earth’s surface is covered by ocean and contains about 97 percent of its surface water and stores huge amounts of energy in the form of heat. Besides, the sea has comparatively large temperature resistance to change. Today, it is understood that the biological and physical performance of the ocean can change rapidly over minute and large areas. It usually decides the timing and models of climate change.

When the heat increases over the ocean it escapes to warm the atmosphere and creates temperature variation in the atmosphere which in turn causes winds. As a result, winds move horizontally over the sea surface to drive ocean motion patterns. The variations in temperature and salinity cause vertical ocean currents which makes the warmer, fresher waters flow upwards as colder, denser or saltier water tends to move down.

Eventually, a complex flow pattern is created through which the warm surface waters move pole ward where heat escapes fast to outer space, as cold, deep currents are established in the sea depths. Because of this complex ocean circulation movement system, the oceans and atmosphere get together to distribute heat and control climate. As this movement conveys huge amounts of heat and as a result more moderate climates on land areas that are nearer the ocean.

It is not surprising to note that man’s increasing needs have simultaneously increased the load of greenhouse gases in the atmosphere. The burning of fossil fuels releases many harmful pollutants particularly the greenhouse gases into the atmosphere and contributes global warming. Increases of greenhouse gases in the atmosphere increases the earth’s temperature and results in malting of glaciers and ice sheets (Meehl, et al. 2005).

Scientists estimate that global average air temperature near Earth’s surface raised 0.74 ± 0.18 °C (1.3 ± 0.32 °F) in just last one century. According to the Intergovernmental Panel on Climate Change (IPCC), “most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations,” (IPCC, 2007).

Hurricane and its Causes

Hurricanes are natural disasters that are characterised by large tropical storms with heavy winds. Hurricanes generally contain winds in excess of 74 mph or 119 km per hour and large areas of rainfall. Besides, they have the potential to produce dangerous tornadoes. There are serious damages to life that has resulted from the hurricanes. The strong winds and excessive rainfall in general produce abnormal rises in sea levels resulting in flooding (Kreger, 2005).

According to the National Hurricane Center, “hurricane” is a name for a tropical cyclone that occurs in the Atlantic Ocean. “Tropical cyclone” is the common term used for low-pressure systems that build up in the tropics. Tropical cyclones with maximum sustained surface winds of less than 17 meters per second (39 mph / 62.7 kph / 34 knots) are termed as tropical depressions. Once the tropical cyclone reaches winds of at least 17 meters per second (m/s), it is typically called a tropical storm. Further if winds reach 33 m/s (74 mph / 119 kph / 64 kt), then it is called a “hurricane.”

Hurricanes are very common and every year the hurricane season extends between June 1 and November 30. The most common places of occurrence are the eastern and gulf coasts of the United States, Mexico, Central America and the Caribbean. In the rest of the world, the same types of storms are called typhoons or cyclones. Hurricanes can kill thousands of people and cause billions of dollars of property damage when they hit heavily populated areas.

Scientists have tried to classify hurricanes on the basis of a scale named the Saffir-Simpson Scale which measures hurricanes by strength. The reading of the scale varies between 1 and 5, with 5 being the strongest. The number of hurricanes with the scale of five has been very few. For instance, the most famous storms Hurricane Andrew measured 4 in the Saffir-Simpson Scale. This storm is known to have caused 30.475 billion dollars damage and killed 23 people. Besides, it is also estimated that hurricanes needs a temperature of about 26-27°C waters to form (personal.psu.edu, N.D.).

Global Warming and its Impact on Hurricanes

Though global warming cannot be the only reason for hurricanes and its increasing strength, many scientists believes that it is one of the reasons. Scientific evidence point out that global warming is making hurricanes stronger and more destructive as the years pass by. Though no one can precisely say to what extend the global warming is responsible for the 2005 hurricane season, it has played a major role in it.

The Intergovernmental Panel on Climate Change acknowledged in its 2001 Third Assessment report that: “Peak wind intensity and mean and peak precipitation intensities of tropical cyclones are likely to increase”. The link between Global Warming and Hurricanes can be explained in a simple form. It is a well known fact that warm water is the source of energy for hurricanes and as the global warming progresses, the oceans become warmer and in turn result in hurricanes (cleartheair.org, 2007).

There are several studies that say that global warming is responsible for the increasing strength of Hurricanes. For instance, during the summer of 2005, two studies by different research teams using different methodologies support this fact. According to MIT Professor Kerry Emanuel pointed out a very strong connection between hurricanes’ Power Dissipation Index (PDI- a measure of a hurricane’s wind speed), strength and duration and sea-surface temperature in the North Atlantic and North Pacific tropical oceans. This report was published in the article entitled -Increasing destructiveness of tropical cyclones over the past 30 years, Nature. Additionally, Dr. Emanuel found that PDI increased more than 40% during the period that sea surface temperatures raised just 0.5ºC. Dr. Emanuel found that “the large upswing in the last decade [in SST] is unprecedented, and probably reflects the effect of global warming” in combination with natural cycles (Emanuel, 2005).

In Georgia Institute of Technology researchers Drs. Peter Webster and Judith Curry found that the number of storms that reach category four and five in the Saffir-Simpson Scale are the most powerful, damaging hurricanes and they found that these strong hurricanes has nearly doubled over the past 35 years. Their study included all six of the world’s tropical ocean basins and found that the increase in hurricane strength correlates with a rise in sea surface temperatures around the world of about 1ºF (0.5ºC) between 1970 and 2004 (Webster and Curry, 2005).

Additionally, they also found that factors other than sea surface temperatures could also be considerably contributing to the recent years strengthening hurricanes. They studied the following factors vertical wind shear i.e. the measure of changes in wind speed and direction with height; humidity in the lower atmosphere; and zonal stretching deformation, which is the tendency of the winds to rotate in a cyclonic direction. The results showed that surface sea temperatures were the main influences in the global and north Atlantic hurricane intensity increases (Komar and Allan, 2007).

The key connection is that between sea surface temperatures (SST) that is influenced by the global warming and the power of hurricanes. This can be explained in simple manner- warm water which result in the instability in the lower atmosphere forms the major energy source of hurricanes.

This is the reason they only arise in the tropics and during June to November in the tropical North Atlantic as it is the season when SSTs are highest. Besides, the El Nino/Southern Oscillation tend to influence in the case of Atlantic hurricanes. There has been research to find the reasons for Katrina and here again scientist pointed out that hurricanes have a tendency to turn into more destructive as ocean temperatures rise, and rise in greenhouse gas resulting in the warming of oceans (Rahmstorf, et al. 2005).

Hurricanes in the East coast of the United States

East coast of the United States is one of the most vulnerable places hit by several hurricanes. In fact, hurricanes form both in the Atlantic basin to the east of the continental United States and in the Northeast Pacific basin to the west of the United States. Fortunately, the ones in the Northeast Pacific almost never hit the United States, while the ones in the Atlantic basin hit the United States mainland on an average less than twice a year.

Scientists have attributed two main reasons for this. Research has found that hurricanes have a tendency to move towards the west-northwest once they form in the tropical and subtropical latitudes. On the other hand in the Atlantic, similar motion regularly brings the hurricane into the vicinity of the United States east coast. Meanwhile, a west-northwest track takes those hurricanes farther off-shore in the Northeast Pacific, away from the United States west coast. Many have predicted that in the coming years if the greenhouse gases are not controlled, it is possible that these can cause serious damage.

Additionally it is common to note that along the U.S. east coast, the Gulf Stream provides a source of warm waters which again increase the incidences of hurricanes. On the other hand along the U.S. west coast, the ocean temperatures rarely gets warmer even in the midst of summer and therefore cool temperatures are not energetic enough to maintain a hurricane’s strength (Landsea, 2007).

Studies point out that ocean wave height which is yet another factor for hurricanes along the U.S. Atlantic coast report a raise during the summer months when hurricanes are most significant to wave generation. For instance, wave heights more than 3 meters can be recognized to specific hurricanes, have increased on average by 0.7–1.8 meters in the past three decades. In the recent decades the most intense hourly averaged wave heights generated by major hurricanes have increased from about 7 meters of the buoys to more than 10 meters. This raise in wave heights can be ascribed in large part to a progressive strengthening of the hurricanes, which Emanuel (2005) has recorded through his analyses of hurricane wind speeds.

Even though there has been an increase in the numbers of hurricanes, there is considerable variation from year to year. Emanuel (2005) recorded the most likely explanation for the rising wave heights that there has been a progressive strengthening of the hurricanes, based on analyses of the wind speeds measured within the storms and the primary factor important to the generation of waves. With the raise in hurricane intensities and wind speeds, increased ocean-water temperatures brought about by global warming, the heights of the waves they generate may continue to increase into the future, bringing even greater hazards to communities along the shores of the U.S. west coast (Komar and Allan, 2007).

Effects on Sea Animals Near the Coast

It is a natural tendency that the growth and abundance of the ocean’s phytoplankton decreases when the climate gets warmer which can affect the marine life since the phytoplankton is a source of food for krill, fish and whales. There was a rise in ocean’s temperature since last fifty years and data from NASA shows the growth and abundance of phytoplankton around the world is decreasing. These findings are critical since it indicate effect of the changing global climate.

It is estimated that phytoplankton is accountable for about half of Earth’s photosynthesis action, a method which takes carbon dioxide from the atmosphere and converts it into organic carbon and oxygen that needed for every ocean ecosystem. It is observed that since 1999, the climate was getting warmer and has seen the health of ocean plants diminish. The NASA’s satellite data helps scientists to resolve the amount of phytoplankton and the growth rates. There is an agreement among the world’s scholars that carbon dioxide, methane and other greenhouse gases generated from the burning of fossil fuels have added to natural carbon dioxide levels (Kay, 2006).

Katrina was among the greatest disaster that struck United States, in terms of devastated cities and communities. Unlike human beings and the modern technologies, animals have the capability to sense these natural disastrous and escape. For instance, in Florida, animals showed a firm ability to forecast the disaster and save themselves. Similarly, South Florida Sun-Sentinel author comments, “When Hurricane Charley came within hours of the Caloosahatchee River, eight sharks tagged by biologists suddenly bolted out of the estuary to the safety of the open ocean” (Pasichnyk, 2005).

In general, hurricanes can cause a raise in ocean water turbidity, sedimentation, nutrient release, and low dissolved oxygen levels, all of which ultimately have a devastating impact on the sea animals. Additionally, strong wave action during hurricanes has caused breakage and die-off of invertebrates such as corals and sponges. However, larger vertebrates are not much affected. In the year 1992, after Hurricane Andrew in southern Florida, deposited sediment smothered many sponges (Tilmant et al. 1994). Similarly, sea whips and lobsters were missing from the sea. Additionally, the populations of sea animals are also affected by the pollutants that include marine debris, fuel, and oil spills (NOAA 2005).

Conclusion

When the oceans warm up the rate at which the atmosphere warms up slowly retards. The greenhouse gases, ocean circulation, ocean temperatures, and melting of glaciers and sea ice, will determine the global warming which in turn will determine the speed of global climate change. In conclusion, there exists a delicate balance of ocean-atmospheric system between incoming and outgoing energy, if for any reason due to manmade or any other natural reasons this balance is disturbed even to a minute level, global climate can undergo a series of complex changes.

Finally, it can be said that the duration and strength of hurricanes have increased over the last three decades and in the future it will continue to increase. Global warming is a major contributing factor for hurricanes as it is directly linked with the rise in temperature of the oceans. As mentioned earlier the oceans have a tremendous capacity for storing heat energy. Therefore, it is essential that government, policy makers, scientist and public work hand in hand to bring down the greenhouse gases and thereby reduce the global warming. Since ocean temperatures may be increasing more quickly than atmospheric temperatures, it is vital to take action to bring down these emissions.

References

cleartheair.org, (2007) Hurricanes and Global Warming, Retrieved on 17 October 2007 from https://www.cleartheair.org

Emanuel, K. (2005) Increasing destructiveness of tropical cyclones over the past 30 years, In: Nature Vol. 436, pp 686-688.

IPCC, (2007) Climate Change 2007: The Physical Science Basis, Intergovernmental Panel on Climate Change

Kay, J. (2006) Ocean warming’s effect on phytoplankton, December 7, 2006, San Francisco Chronicle, pp A – 12. Retrieved on 16 October 2007 from https://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/12/07/MNG1JMQUL01.DTL

Komar, P.D. and Allan, J.C. (2007) Higher Waves Along U.S. East Coast Linked to Hurricanes, EOS, Vol. 88, No. 30, pp 301–308.

Kreger, C. (2005) Hurricanes, Retrieved on 16 October 2007 from https://www.cotf.edu/ete/modules/sevweath/swwhatare.html

Landsea,C. (2007) 46 Why do hurricanes hit the East coast of the U.S., but never the West coast?, Retrieved on 16 October 2007 from https://stason.org/

Meehl, G.A. et al. (2005) How Much More Global Warming and Sea Level Rise? Science, 18 March 2005: Vol. 307. no. 5716, pp. 1769 – 1772.

Webster, P.J. and Curry, J.A. (2005) Hurricanes Are Getting Stronger, Study Says, Georgia Institute of Technology,  Retrieved on 17 October 2007 from https://www.gatech.edu