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A hurricane is a tropical cyclone or storm. They’re called hurricanes when they occur in the Atlantic Ocean, typhoons when they occur in the Pacific Ocean, and cyclones in the Indian Ocean. They are an example of nature’s fiercest fury.
Hurricanes are one of the world’s most costly natural disasters. In some cases, they’ve caused over 100 billion dollars in damage. Hurricanes are low-pressure systems, often with thunder and lightning. They usually form over the tropics and subtropics.
The formation of hurricanes is rather a simple process. It all starts with an atmospheric disturbance in or near a tropical ocean. The disturbance can evolve into a tropical system with warm enough water temperatures (usually around 26oC) and supportive atmospheric conditions. In the Atlantic, the system first develops into a tropical depression. With favorable atmospheric conditions and temperatures, it can grow stronger and graduate to a tropical storm. We call this storm a hurricane when its wind speeds rise over 74 mph (miles per hour).
The hurricane’s wind speeds determine its category. Category 1 hurricanes are those with wind speeds over 74 mph. Category 3 or higher hurricanes have wind speeds greater than 111 mph. Category 3 and higher hurricanes are ‘major hurricanes’.
Between 1996 and 2009, the average number of tropical storms that occurred in the Atlantic was around 11 per year, with about six evolving into hurricanes. But between 2000 and 2014, on a yearly average, 15 tropical storms were forming in the Atlantic, with around 7 becoming hurricanes.
The warmer the ocean gets, the more heat energy is available. This means that warmer waters increase the potential for tropical cyclones to develop. Therefore, we can safely assume that as we release more planet-warming emissions, the likelihood of tropical cyclone activity will increase.
In this article, we’re going to see are hurricanes becoming more intense with climate change.
A 2013 study found that the proportion of the strongest hurricanes has substantially increased regionally and globally. With hurricanes becoming more intense, scientists have attributed this increase to global warming. The study says that since 1975, category 4 and 5 hurricanes have increased by 25-30% with every degree increase in global temperatures.
Scientists define the intensification of a hurricane as an increase in wind speeds by at least 35 mph in 24 hours. A recent study examined the hurricane record in the Atlantic basin from 1986 to 2015. The study found that with every decade, hurricane intensification increased by 4.4 mph. The study’s authors said that the increase in the intensity of hurricanes is due to a shift of the Atlantic Ocean into a warmer phase. This shifting of temperatures in the Atlantic is called the Atlantic Multidecadal Oscillation and is a natural cycle.
However, scientists at NOAA’s Geophysical Fluid Dynamics Laboratory (NOAA GFDL) have suggested that global warming is also playing a role in hurricane intensification. They used the HiFLOR, the most advanced climate model available, to simulate hurricanes. The team concluded that climate oscillations like the Atlantic Multidecadal Oscillation could not explain the observed hurricane trend. The team says they cannot confidently attribute hurricane intensification to human-caused global warming. However, they have said that human-caused global warming significantly increases cyclone intensification rates in the HiFLOR model.
When we try to find a link between a warming world and weather, one of the most well-understood connections is increased rainfall. The warmer the air, the most moisture it can hold. Therefore, warmer air produces more precipitation. Generally, increased rains follow the Clausius-Clapeyron equation. The equation says that the atmosphere can hold 7% more moisture for every one degree Celsius increase in atmospheric temperature.
Tropical cyclones boost rainfall. The convergence of moisture into a storm, along with higher precipitation, leads to greater intensity and growth. Therefore, a combination of warmer water and air leads to increases in rainfall beyond the simple relationship defined by the Clausius-Clapeyron equation.
Using the HiFLOR model, scientists have found that there will be a global increase in storm frequency between 9% and 23% in the Atlantic by the end of the 21st century. However, they say that we shouldn’t entirely rely on the results of the model. But there is growing confidence among the scientific community that warmer ocean temperatures and rising sea levels intensify the intensity and impacts of hurricanes.
Warmer sea temperatures could intensify hurricane wind speeds, allowing them to deliver more damage. NOAA has suggested that we could witness a 10% increase in wind speeds of category 4 and 5 hurricanes. A warming sea is also causing hurricanes to deliver more precipitation. In a 2oC warming scenario, hurricanes will provide 10-15% more rainfall than they do today.
Scientists cannot make accurate predictions about the intensity of hurricanes as climate change progresses. However, they have said that it is likely the number of coastal storms will stay the same or even decrease. But there will be an increase in the occurrence of the most extreme storms. Previous research has shown that there will be no change or a slight reduction in hurricane frequency in the 21st century. However, more recent work suggests that as warmer ocean temperatures boost hurricane intensity, fewer storms will actually form.
Rising sea levels are likely to make hurricanes and coastal storms more damaging. On a global average, scientists expect sea levels to rise by 1-4 feet if greenhouse gas emissions remain moderate during this century. The sea-level rise will amplify coastal storm surges. For example, the increase in sea levels intensified the impact of Hurricane Sandy in 2012. Hurricane Sandy caused an estimated 65 billion dollars in damage in Connecticut, New Jersey, and New York. Coastal flooding was responsible for much of this flooding.
High global temperatures are causing the tropics to expand. This means that hurricanes can now form over a much larger area than before. The areas affected by hurricanes are moving toward the poles. This changing pattern of hurricane formation puts much more property and human lives at risk. But we need more research to better understand how these patterns might change in the future.