This has truly been an amazing hurricane season. From Tropical Storm Arlene in the second week of June to Hurricane Epsilon in the first week of December, the only rule of this hurricane season was that there were no rules. The 2005 hurricane season saw 26 tropical storms, 14 hurricanes, and 7 major hurricanes. This year was the first time that the Atlantic saw three Category 5 hurricanes in one year. In fact, in one year alone the Atlantic saw the first, fourth, and sixth most intense hurricanes on record. This season saw more than double the average 11 tropical storms, 6 hurricanes, and 2 major hurricanes.
By now everyone has heard that this was the most active hurricane season on record. Not only did we use the Greek alphabet for naming storms for the first time ever, we used it 5 times! Two of those letters, Beta and Epsilon, strengthened into hurricanes and Beta even reached Category 3 strength. Epsilon became a rare December hurricane after the season was officially over. There is a great deal of talk about changing the hurricane naming scheme to reflect this use of the backup list of names. Problems are likely to arise when the issue of retiring names comes up this winter, as cases are being made for retiring Alpha, Beta, and Gamma.
This year produced no shortage of storms for the record books. Hurricane Vince became the first tropical cyclone to ever strike the Iberian Peninsula when it struck Spain. Tropical Storm Delta moved over the Canary Islands and almost became the first storm to make landfall over Morocco. Hurricane Epsilon repeatedly defied forecasters and actually strengthened within an area where it wasn't expected to be able to survive. This was the first year that four major hurricanes struck the United States. Hurricane Wilma became the most intense hurricane ever recorded in the Atlantic basin, bottoming out at 882 mb compared to the average sea level pressure of 1013.25 mb. Wilma ran directly over Cozumel and Cancun then turned towards Florida and did a surprisingly amount of damage in southeast Florida considering it was only a Category 1 hurricane at that time. At 897 mb, Hurricane Rita became the most intense hurricane ever recorded in the Gulf of Mexico and the 4th most intense hurricane ever recorded in the Atlantic.
Then, of course, there was Katrina, the 6th most intense storm on record at 902 mb. While numbers remain unclear, the official death toll was 1,325 killed, the third highest in US history (behind the Galveston Hurricane of 1900 and the Okeechobee Hurricane of 1928). Damage estimates range from $80 to $130 billion, at least double the previously most expensive Hurricane Andrew. Katrina has easily become the most expensive natural disaster in U.S. history. Katrina underlined several deep rooted problems in this country. Katrina exposed for the world to see the fact that this country still has glaring socioeconomic inequalities. Katrina made it clear to everyone that local and state governments are simply incapable of responding to large-scale disasters in which the first-responders are themselves the victims. Katrina was a disaster waiting to happen. For decades meteorologists and other scientists had been warning the country about this very scenario. No one can claim that they didn't know the situation would eventually be this bad, but for political and budget reasons nothing was done to prepare.
This incredible devastation has left many wondering if there is a force at work creating these more devastating storms. After the last two hurricane seasons it is clear that hurricanes are getting more intense and more frequent. NOAA reports: There is consensus among NOAA hurricane researchers and forecasters that recent increases in hurricane activity are primarily the result of natural fluctuations in the tropical climate system known as the tropical multidecadal signal. The tropical climate patterns now favoring very active hurricane seasons are similar to those seen in the late 1920s to the late 1960s. The current active hurricane era began in 1995, meaning the nation is now 11 years into an active era that could easily last several decades (20-30 years or even longer). We can expect ongoing high levels of hurricane activity -- and, very importantly, high levels of hurricane landfalls -- as long as the active era continues. However, this consensus does not extend beyond NOAA. Their stance is supported by others like William Gray at Colorado State. However, the opposition has grown in recent years and more scientists are doubting that natural cycles are completely to blame.
Many in the scientific community feel that NOAA's stance on the issue is a result of political pressure. Fortunately not all researchers work for the government. Kerry Emanuel is a hurricane expert at MIT and the leading authority on the maximum potential intensity of hurricanes. In the past Emanuel had believed that intensity fluctuations were a result of natural cycles and had published papers in support of natural fluctuations. However, recently Emanuel has changed camps and is now warning the world about the influence of human activity on hurricanes. He feels that a flux of evidence has tipped the scales of hurricane influences in favor of a global warming causality. Global warming itself is a theory that used to draw skepticism from across the world. However, today it is commonly accepted throughout the scientific community that global climate change is real and is a result of increased carbon dioxide emissions.
There are many issues with determining the cause of these changes in hurricane intensity. Reliable data on hurricane intensity and frequency only extends back to the 1950s. Changes in the instruments used to measure atmospheric conditions also induces inconsistencies in the available data. With this taken into account, we can only accurately say that a period of high hurricane activity in the 1950s and 1960s gave way to a lull that continued until the mid 1990s. During the past ten years hurricane activity has again been on the uptick. That generally pattern since the 1950s is agreed upon by both sides of the debate. There is evidence that prior the 1950s there was a preceding quieter period which is also generally accepted by most, though not all, climate experts. However, the magnitude of this lull is not known to same degree of accuracy as the one in the late 20th century.
Proponents of natural cycles forcing hurricane activity point to the increase, subsequent decrease, and most recent increase in activity as a clear sign that hurricane activity varies regularly and naturally. However, those who take the side of global warming offer a different explanation of this pattern.
Dr. Emanuel claims that hurricane activity during the nineteenth century was fairly constant and lower than that of today. He claims that the onset on global warming during the early twentieth century caused the hurricane activity increase until the peak in the 1950s and 1960s and is again causing the increase visible today. It is the lull during the late twentieth century that opponents of global warming forcing point to as a flaw with the theory. However, Emanuel and others have proffered a well documented phenomenon known as global dimming to explain the temporary suppression of hurricane activity.
The basic theory behind global dimming is that increased pollution of dust, soot, and other small particles during the 20th century led to a apparent dimming of the Earth. As more particulates were pumped into the atmosphere, water condensed onto the particles and reflected sunlight back into space. As a result, the increased pollution actually acted to counter global warming by reducing the amount of the sun's energy reaching the ground. Global dimming has been well documented and is believed to be a real phenomenon. Human induced global dimming peaked in 1989 as more pollution controls decreased the dimming after that point. The same pollution that caused global dimming were also responsible for acid rain. Therefor action was taken to control acid rain and global dimming was reversed before it was even realized to exist. The observed maximum period of dimming actually occurred in 1991 as a result of the eruption of Mount Pinatubo. It is theorized that this dimming downwind of the factories and population centers of the Midwest and Northeast United States could be what led to decreased sea surface temperatures (SSTs) across the North Atlantic. This could have served to suppress the hurricane activity in the late twentieth century and even caused the failure monsoonal rains over the Sahel region of Africa.
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