The jury is still out on what kind of impact global warming will have on big storms like typhoons. In 2005, there was record-breaking 28 named storms around North America, of which 15 were hurricanes. Some said this caused by global warming. There were predictions that 2006 would be a nasty hurricane season but that did not happen.

A study by Kerry Emanuel, an MIT climatologist, released in August 2005 just before Hurricane Katrina, said there had been an marked increase in the intensity and duration of tropical storms since the 1970s. It is said the number of Category 4 and 5 storms worldwide had doubled and the wind speed and duration if all hurricanes gad jumped 50 percent.

Stronger and More Frequent Typhoons?

Some climatologists believe that the surge in the number of typhoons and hurricanes in recent years may be linked to global warming which warms up the seas and provides more energy for weather phenomena that develop into severe storms. In 1995, there were unusually high number of hurricanes. Coincidently or not, 1995 also had the highest global surface temperatures on record. and ocean temperatures in the Atlantic were the highest ever recorded. In one of the 11 years between 1995 and 2005 there were unusually high numbers of hurricanes.

There are generally more major hurricanes in years when the sea surface temperatures are higher than average. Sea temperatures in the Atlantic Ocean rose steadily from 2000 to 2004, and each of these years had an “above normal” hurricane season with the exception of 2002 which was a weak El Nino year. But the Atlantic patterns fluctuates and are not consistent. The mid 1920s through the 1960s were very active when temperatures were relatively cool. The 1970s and the early 1990s were quiet.

There was a particularly high number of typhoons in 2004. By August of that year there had already been nineteen, 35 percent more than normal. Ocean temperatures in 2004 were around two degrees F higher than normal. The year 2005 was a bad year for hurricanes. There were 27 named tropical storms---including Katrina, which killed more tha 1,000 people and lef much of New Orelans and the neigboring coast in ruins---so many the list of storm names was extended with Greek letters. There were a record 15 hurricanes, including foru category 5 storms.

Some scientist have suggested that global warming will increase the rain fall from typhoons by 20 percent anc increase their winds by 10 percent. Damages is also worsening because more intense typhoons are coinciding with rising seas levels. But not all the damage is the fault of the storms. Damage typhoons is also increasing because more people than ever live on coastlines or other vulnerable areas.

In the 1970s, AP reported, “there was an average of about 11 storms of the powerful category 4 and 5 range. Since 1990 that has climbed to an average of 18 per year worldwide, researchers led by Peter J. Webster at the Georgia Institute of Technology report in Friday’s issue of the journal Science. There was no increase in the total number of tropical storms worldwide, the change was in how many of them grew into the most dangerous categories.”[Source: AP, September 15, 2005]

“In their analysis of hurricanes “ known as typhoons or cyclones in other parts of the world “ the researchers counted 16 category 4 and 5 storms in the Atlantic-Caribbean-Gulf of Mexico in 1975-1989. This increased to 25 in the 1990-2004 period.In the eastern Pacific the increase was from 36 to 49 storms and it went from 85 to 116 in the western Pacific. In the southwest Pacific the increase was from 10 to 22 powerful storms, while the total went from one to seven in the north Indian Ocean and from 23 to 50 in the south Indian Ocean. [Ibid]

In 2005, the Atlantic basin produced more tropical storms, 28, and more full-blown hurricanes, 15, than any year in at least the past half century. Last year, memorable for its four major hurricanes, could also lay claim to three of the six strongest storms on record.

Stronger More Frequent Storms Because of Global Warming?

The increase in powerful hurricanes between the 1970s and 1990s coincides with a rise of nearly 1 degree Fahrenheit in the tropical sea surface temperature around the world according to the research by the team led by Peter J. Webster at the Georgia Institute of Technology. Some interpret the changing number of storms to be part of natural variability. But the variability in the past has been over 10 year periods, and this is sustained over 30 years, a maber of Webster’s team said. [Source: AP, September 15, 2005]

Kerry Emanuel, a climatologist at Massachusetts Institute of Technology, reported in August in the journal Nature that hurricanes in both the Atlantic and Pacific have increased in duration and intensity since the 1970s. In his study, which was based in his analysis of wind speed reports by the National Hurricane Center and other sources, he said the accumulated power of Atlantic hurricanes has more than doubled in the past 30 years, with a particularly dramatic spike since 1995, and global warming likely is a major cause. On the particularly steep increase that began in 1995, when 19 tropical storms and hurricanes and high ocean temperatures were recorded , Emanuel wrote: "This large increase in power dissipation over the past 30 years or so may be because storms have become more intense, on the average, and/or have survived at high intensity for longer periods of time.” On the one degree increase in the average ocean surface temperature, Chris Landsea, an NOAA scientist on Virginia Key and one of the nation's leading hurricane researchers said, "It sounds like a small amount, but we know that as waters get even a little bit warmer, the potential exists for hurricanes to get dramatically stronger," said

Madeleine Nash wrote in Smithsonian magazine, A few weeks before Hurricane Katrina struck Emanuel “published evidence in the journal Nature that hurricanes in both the North Atlantic and the western basin of the North Pacific had undergone a startling increase in power over the past half century. The increase showed up in both the duration of the storms and their peak wind speeds. The cause, Emanuel suggested, was a rise in tropical sea surface temperatures due, at least in part, to the atmospheric buildup of carbon dioxide and other heat-trapping gases caused by the burning of fossil fuels. [Source: Madeleine Nash, Smithsonian magazine, September 2006]

“Even scientists who would expect hurricanes to intensify in response to greenhouse warming were stunned by Emanuel's suggestion that global warming has already had a profound effect. Computer simulations of a warming world, notes climate modeler Thomas Knutson of the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, suggest that by the end of this century, peak sustained wind speeds could increase by around 7 percent, enough to push some Category 4 hurricanes into Category 5 territory. But Knutson, along with many others, did not think that the intensity rise would be detectable so soon---or that it might be five or more times larger than he and his colleagues anticipated. "These are huge changes," Knutson says of Emanuel’s results. "If true, they may have serious implications. First we need to find out if they’re true." [Ibid]

“Emanuel’s paper raised the ante in what has grown into an extremely intense debate over the sensitivity of the earth's most violent storms to gases spewed into the atmosphere by human beings. In the months since the dispute began, dozens of other studies have been reported, some of which support Emanuel's conclusions, others of which call them into question. The debate has grown so impassioned that some former colleagues now scarcely speak to one another. As Emanuel sees it, sea surface temperatures are important because they tweak a fundamental dynamic that controls hurricane intensity. After all, storm clouds form because the ocean's heat warms the overlying air and pumps it full of moisture. And the warmer the air is, the more vigorous its rise. [Ibid]

Why Are There More Typhoons Some Years Than Other Years

There were far fewer hurricanes and tropical storms in the Atlantic basin in 2006, far fewer than meteorologists predicted before the hurrican season began, even though waters were a half degree to two warmer than average, an indicator some say of more storms.

Madeleine Nash wrote in Smithsonian magazine, For years scientists have been pondering why the number of Atlantic hurricanes varies from year to year, even though roughly the same number of African waves move out over the ocean each year. What accounts for the difference? El Niño explains some, but not all, of the variance. By combing through the historical record and more recent recordings from scientific instruments, Gray, along with NOAA meteorologist Christopher Landsea, has found another pattern: hurricanes in the Atlantic march to a slowly alternating rhythm, with the 1880s and 1890s very active, the early 1900s comparatively quiescent, the 1930s through 1960s again active, 1970 through 1994 quiescent again. [Source: Madeleine Nash, Smithsonian magazine, September 2006]

“In 2003 “a possible explanation for this pattern emerged. NOAA meteorologist Stanely Goldenberg explained using a graph that plots the number of major hurricanes---Category 3 or higher---that spin up each year in the Atlantic’s main hurricane development region, a 3,500-mile-long band of balmy water between the coast of Senegal and the Caribbean basin. Between 1970 and 1994, this region produced, on average, less than half the number of major hurricanes that it did in the decades before and after. Another graph shows a series of jagged humps representing the Atlantic multi-decadal oscillation, a swing of sea surface temperatures in the North Atlantic that occurs every 20 to 40 years. The two graphs seem to coincide, with the number of major hurricanes falling as waters cooled around 1970 and rising as they began warming about 1995. [Ibid]

“Scientists have yet to nail down the cause of the multi-decadal oscillation, but these striking ups and downs in surface temperatures appear to correlate’somehow---with hurricane activity. "You can't just heat up the ocean by 1 degree Celsius and Pow! Pow! Pow! get more hurricanes," says Goldenberg. More critical, he thinks, are atmospheric changes---more or less wind shear, for example---that accompany these temperature shifts, but what comes first? "We still don't know which is the chicken and which is the egg," he says. "The ocean tends to warm when the trade winds get weaker, and the trade winds can get weaker if the ocean warms. Will we lock it down? Maybe someday." [Ibid]

Critics Stronger More Frequent Storms and Global Warming

Ap reported: “Christopher Landsea, a meteorologist at the National Oceanic and Atmospheric Administration’s Hurricane Research Division in Miami, questioned the data showing an increase in major storms, saying the estimates of the wind speed in storms in the 1970s may not be accurate. “For most of the world there was no way to determine objectively what the winds were in 1970,” he said. The techniques used today were invented later, he said. The Atlantic-Caribbean-Gulf of Mexico region is the best monitored in the world and that region had the smallest increase, he noted. [Source: AP, September 15, 2005]

Landsea said the 1995-04 spike in accumulated hurricane power correlated precisely with the beginning of the period of increased hurricane formation. "It's very difficult to separate out what's caused by this natural cycle of activity versus man-made warming," Landsea said. He also raised concerns about some statistical procedures employed by Emanuel, whom he described as ``a very respected researcher." "This is a serious study and it needs to be taken seriously," Landsea said. ``But when you take a close look at it, there's a lot of caveats. So, at this point, I'm not convinced he's found the smoking gun between global warming and hurricanes."[Source: Martin Merzer, Miami Herald, August , 2005]

Madeleine Nash wrote in Smithsonian magazine, “For their part, Emanuel's critics, Goldenberg and Landsea among them, don't utterly discount ocean warmth. They just put far more emphasis on other factors like wind shear as the main determinants of storm intensity. Goldenberg and Landsea, for example, grant that greenhouse gases may be contributing to a slight long-term rise in sea surface temperatures. They just don't think the effect is significant enough to trump the natural swings of the Atlantic multi-decadal oscillation. "It's not simply, yes or no, is global warming having an effect?" says Landsea, the science and operations officer for the National Hurricane Center. "It's how much of an effect is it having?" [Source: Madeleine Nash, Smithsonian magazine, September 2006]

“Emanuel says that much of the cooling in the tropical North Atlantic in the 1970s can be traced to atmospheric pollutants, specifically to a haze of sulfurous droplets spewed out by volcanoes and industrial smokestacks. Global climate modelers have recognized for years that this haze in the atmosphere acts as a sunshade that cools the earth's surface below. Emanuel says that now that this form of air pollution is on the wane (and this is a good thing for all sorts of reasons having nothing to do with hurricanes), the warming influence of greenhouse gas pollution, and its effect on hurricanes, is growing ever more pronounced. "We will have some quiet [hurricane] years," he says. "But unless we have a really big volcanic eruption, we'll never see another quiet decade in the Atlantic in our lifetime or that of our children." [Ibid]

Typhoons and El Nino

Madeleine Nash wrote in Smithsonian magazine, “Among the known regulators of vertical wind shear is El Niño, the climate upheaval that alters weather patterns around the globe every two to seven years. During El Niño years, as Colorado State University tropical meteorologist William Gray was first to appreciate, high-level westerlies over the tropical North Atlantic increase in strength, ripping developing storms apart. In 1992 and 1997, both El Niño years, only six and seven tropical storms formed, respectively, or a quarter of the number in 2005. (Then again, the devastating Hurricane Andrew was one of the 1992 storms.) [Source: Madeleine Nash, Smithsonian magazine, September 2006]

Modifying Typhoons

In 2004, AP reported: “Imagine a world where microwave beams, a biodegradable oil slick or a shower of silver iodide from a plane would be enough to weaken or deflect a hurricane, saving thousands of lives. Scientists say applications are decades away but the research is under way.The techniques under study have not been tested on a real hurricane, but researchers using computer models say they have practiced introducing variations in precipitation, evaporation and air temperature to sap a hurricane's strength or redirect it. [Source: AP, October 29, 2004]

The researchers say these changes could be brought about by beaming microwaves from a satellite to heat water vapor around a storm, or by using a biodegradable oil slick to limit ocean evaporation, the source of a storm's energy. "Our research shows that modifying hurricanes could be possible one day," said Ross Hoffman, lead scientist with the U.S.-based consulting firm Atmospheric and Environmental Research Inc. Hoffman published an article about his research in this month's Scientific American magazine. Funded by a $500,000 NASA grant, Hoffman said he has simulated 1992 hurricanes Iniki and Andrew and introduced subtle changes in computer models that altered the storms.

For Hurricane Iniki, which ravaged the Hawaiian island of Kauai, Hoffman changed conditions including temperature and humidity, and the simulated hurricane took a 60-mile swing west, missing Kauai. With Andrew, the simulated hurricane still had damaging winds in Florida and the Bahamas but it was reduced from a severe Category 3 to Category 1.

Some experts are skeptical of fiddling with nature. The basic concept of Hoffman's research is sound but modifying hurricanes likely won't be possible anytime soon, said Frank Marks, of the National Oceanic and Atmospheric Administration's lab in Miami. "It's kind of silly at this point," said Marks, director of hurricane research for the lab. "People don't realize how much energy we're talking about and the area involved. It's immense."

Techniques for Modifying Typhoons

Storm modification methods that have been suggested include cooling the tropical ocean with icebergs and spreading particles or films over the ocean surface to inhibit storms from evaporating heat from the sea. Hoffman’s research suggests microwaves beamed from space could weaken or move storms. In a separate project, research and inventing company Dyn-O-Mat Inc. Has proposed weakening storms by dispersing a super-absorbent powder, turning a hurricane's moisture into solidified gel. Company president J.D. Dutton said the powder “ a "polymer-based substance" “ has made clouds dissipate when sprinkled over them. T [Source: AP, October 29, 2004]

Dyn-O-Mat has contracted Evergreen International Aviation Inc., based in McMinnville, Oregon, to spray its powder from planes during next year's hurricane season, which runs from June 1 to Nov. 30. The company doesn't need permission from any authority because the trials would be done over international waters, Dutton said. He said the powder used is nontoxic and the environmental effects would be minimal.

The Washington Post reported: Moshe Alamaro has proposed getting “a fleet of ocean barges and mount 10 or 20 jet engines “ tails up “ on each one. Fill the barges with aviation fuel and tow them into the path of an oncoming hurricane. Light off the jets. If everything goes as planned, the jets will trigger small tropical storms, "like backfires," Alamaro says, marginally lowering the surface ocean temperature and depriving the real hurricane of energy as it gets closer to shore. Alamaro's "free jet" plan is designed to create a temperature perturbation. He said he could test the concept -- in a remote part of the Pacific and in the hurricane off-season -- for about $10 million, by using junker jet engines from mothballed B-52s in Arizona. "We have the jets and the barge, but we don't have knowledge about the effects and we don't have the knowledge about hurricanes," Alamaro said in a telephone interview. "A test would entice the necessary studies to make it feasible."[Source: Guy Gugliotta, Washington Post, October 3, 2005]

Operation Stormfury

AP reported: “The U.S. government conducted hurricane research between 1962 and 1983 in a project dubbed "Stormfury." Government planes seeded clouds surrounding a hurricane's eyewall with silver iodide, which was supposed to alter the storm's eye and cause decreased wind. "The results were ambiguous and the program was discontinued," Marks said. While wind speeds decreased by 10 to 30 percent in four hurricanes, it couldn't be determined whether it was due to human intervention or nature. Hoffman said silver iodide remains a possible tool. During the U.S. project, Cuban President Fidel Castro complained it was a means of warfare because rains and floods devastated the Cuban sugar crop. Mexico also claimed the U.S. research was depriving it of moisture and hurting agriculture. [Source: AP, October 29, 2004]

During Stormfury, scientists also seeded hurricanes in 1963, 1969 and 1971 over the open Atlantic Ocean far from land. Researchers dropped silver iodide, a substance that serves as an effective ice nuclei, into clouds just outside of the hurricane's eyewall. The idea was that a new ring of clouds would form around the artificial ice nuclei. The new clouds were supposed to change rain patterns and form a new eyewall that would collapse the old one. The reformed hurricane would spin more slowly and be less dangerous. [Source: AP, September 22, 2005]

Sometimes, the experiments appeared to work. Hurricane Debbie in 1969 was seeded twice over four days by several aircraft. Researchers noted that its intensity waxed and waned by up to 30 percent. For cloud seeding to be successful, clouds must contain sufficient supercooled water that is still liquid even though it is below 32 degrees Fahrenheit. Raindrops form when the artificial nuclei and the supercooled water combine.

But scientists also learned that hurricanes contain less supercooled water than other storm clouds, so seeding was unreliable. And, hurricanes grow and dissipate all on their own, even forming new walls of clouds called "concentric eyewall circles." This made it impossible to determine whether storm reductions were the result of human intervention. Project Stormfury was abandoned in the 1980s after spending hundreds of millions of dollars.

According to NOAA: “During the Stormfury years scientists seeded clouds in Hurricanes Esther (1961), Beulah (1963), Debbie (1969), and Ginger (1971). The experiments took place over the open Atlantic far from land. The Stormfury seeding targeted convective clouds just outside the hurricane's eyewall in an attempt to form a new ring of clouds that, it was hoped, would compete with the natural circulation of the storm and weaken it. The idea was that the silver iodide would enhance the thunderstorms of a rainband by causing the supercooled water to freeze, thus liberating the latent heat of fusion and helping a rainband to grow at the expense of the eyewall. With a weakened convergence to the eyewall, the strong inner core winds would also weaken quite a bit. For cloud seeding to be successful, the clouds must contain sufficient supercooled water (water that has remained liquid at temperatures below the freezing point, 0̊C/32̊F). Neat idea, but it, in the end, had a fatal flaw. Observations made in the 1980s showed that most hurricanes don't have enough supercooled water for Stormfury seeding to work - the buoyancy in hurricane convection is fairly small and the updrafts correspondingly small compared to the type one would observe in mid-latitude continental super or multicells. [Source: Chris Landsea, Hurrican eResearch Division, Atlantic Oceanographic & Meteorological Labratories, NOAA]

“In addition, it was found that unseeded hurricanes form natural outer eyewalls just as the Stormfury scientists expected seeded ones to do. This phenomenon makes it almost impossible to separate the effect (if any) of seeding from natural changes. The few times that they did seed and saw a reduction in intensity was undoubtedly due to what is now called "concentric eyewall cycles". Thus nature accomplishes what NOAA had hoped to do artificially. No wonder that the first few experiments were thought to be successes. Because the results of seeding experiments were so inconclusive, Stormfury was discontinued. A special committee of the National Academy of Sciences concluded that a more complete understanding of the physical processes taking place in hurricanes was needed before any additional modification experiments. The primary focus of NOAA's Hurricane Research Division today is better physical understanding of hurricanes and improvement of forecasts. [Ibid]

Image Sources: Wikimedia Commons

Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, National Geographic, Smithsonian magazine, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Wall Street Journal, The Atlantic Monthly, The Economist, Global Viewpoint (Christian Science Monitor), Foreign Policy, Wikipedia, BBC, CNN, NBC News, Fox News and various books and other publications.

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© 2008 Jeffrey Hays

Last updated November 2012

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