Global warming and hurricanes - Caymanian Compass

Hurricane Ivan forming over the Islands in September 2004. â€" Photo: File

Although there is a strong consensus among scientists that human-induced carbon dioxide emissions are causing a greenhouse effect and thus raising surface temperatures on Earth, other scientists staunchly oppose the idea. 

One of those opposing scientists is William Gray, a meteorologist who pioneered seasonal hurricane forecasts while working at Colorado State University, where he remains professor emeritus of atmospheric science. 

Among his theories based on his scientific observations, Gray doesn’t believe that carbon dioxide emissions are having any measurable effect on the formation of tropical cyclones. 

Some scientists saw the busy and destructive Atlantic Basin hurricane seasons of 2004 and 2005 as proof that global warming was causing more and stronger hurricanes. Since then, Gray has spent an increasing amount of time studying the effects of carbon dioxide on the hurricane season.  

Speaking at the National Hurricane Conference in Orlando, Florida in March 2012, Gray noted that since he had given over the primary authorship of the Colorado State University seasonal hurricane forecast to his associate Phil Klotzbach in 2006, he has spent much of his time concentrating on the question of whether carbon dioxide has been responsible for the upswing in hurricane activity in the Atlantic Basin since 1995. 

He contends that the scientists who suggest there is a link between carbon dioxide emission and increased hurricane activity are simply wrong. 

“I think Hurricanes aren’t influenced much by CO2,” he said. “If there is [an influence] it’s noise level and you can never know what it is; but it can’t be much.” 

Why more tropical cyclones? 

Gray acknowledges there has been more hurricane activity, particularly when it comes to major hurricanes with sustained winds of at least 111 miles per hour, since 1995. In fact, he showed a slide that indicated in the 17-year period between 1978 and 1994, there were only 27 major hurricanes - an average of 1.6 per year - while in the 17-year period between 1995 and 2011, there have been 65 major hurricanes - an average of 3.8 per year, more than double the previous 17 years. 

However, Gray suggested that the cause of the increase was not due to global warming, but to cyclical variations to thermohaline circulation in the Atlantic Basin. Thermohaline circulation is a phenomenon that links all the oceans of the Earth and caused by seawater density gradients. The density gradients are caused by both heat and the salt content of the seawater. 

This naturally occurring movement of seawater is also known in the Atlantic Basin as the Atlantic Multi-decadal Oscillation because its cycles last several decades. 

Although the science is complicated, the main consequence of the Atlantic Multi-decadal Oscillation is that in times when the thermohaline circulation is strong, sea surface temperatures are anomalously higher in the main areas of topical cyclone development in the Atlantic Basin.  

Gray produced statistics that showed that during the 25-year period between 1970 and 1994, when the Atlantic Multi-decadal Oscillation was weak and there were fewer named storms, hurricanes and major hurricanes than long-term average, the sea surface temperatures between 10 and 15 degrees north and 70 and 40 degrees west were lower than in the 17 years of strong Atlantic Multi-decadal Oscillation that has occurred since then. 

Although the average anomalously higher sea surface temperatures during periods of strong Atlantic Multi-decadal Oscillation is small - less than one degree Fahrenheit - it takes the average temperature over 82 degrees, which is accepted as the temperature needed for hurricanes to strengthen.  

Gray pointed out that the Atlantic Multi-decadal Oscillation has been going on probably for longer than recorded time and that there have always been periods of more hurricane activity. 

“People confuse the multi-decadal changes in hurricanes with global warming,” he said. “The main driver is salt, not CO2; they just got their chemicals wrong.” 

Speaking at a NOAA Climate Workshop in Huntsville, Alabama in 1996, Gray predicted a 25-30 year period of increased major hurricane activity. 

“We expect that these changing [thermohaline circulation] patterns will lead to enhanced intense (or major) hurricane activity in coming years,” he wrote at the time. 

Scientists do not - at least yet - have the ability to predict the onset of strong or weak Atlantic Multi-decadal Oscillation occurrences, but they do know both cycles generally last anywhere from 20 to 40 years. The current strong Oscillation began around 1995 and is therefore expected to persist to somewhere between 2015 and 2035. 

Global warming 

Sea surface temperature is not the only variable that affects tropical cyclone activity; sea level pressure, upper atmosphere wind shear and even Saharan dust also play a role.
This explains why, even during periods of a strong Atlantic Multi-decadal Oscillation, there can be hurricane seasons with normal tropical cyclone activity or less activity that normal.  

Gray said that while having sea surface temperatures at certain levels was important, sea surface temperatures rising above that level wouldn’t necessarily cause more or stronger hurricanes. 

“There is no real correlation between increasing sea surface temperatures and more hurricanes,” he said. “Hurricanes might be a little more frequent or a little less frequent, or a little stronger or a little weaker.” 

He pointed out that the anomalous cyclical increase in sea surface temperatures in the equatorial Pacific Ocean - known as the El Nino Southern Oscillation - creates stronger wind shear in the Atlantic Basin, something known to actually reduce hurricane formation and strengthening.  

Speaking in an interview with Cayman Free Press in 2010, Gray said the theory of the greenhouse effect was that increased carbon dioxide levels trapped infrared radiation in the atmosphere, which in turn warmed the globe and sea surface temperatures. Warmer sea surface temperatures would then create temperature variations - also called lapse rates - between the ocean surface and the upper atmosphere, resulting in more intense thunderstorm clouds and finally giving rise to more tropical cyclones. 

“In a climate sense, if the globe warms a bit the [sea surface temperatures] warm, the upper levels are going to warm some, and the lapse rates aren’t going to change that much,” he said. “The people who have been saying [more CO2 in the atmosphere causes more hurricanes] don’t know how hurricanes work, basically.” 

To illustrate that carbon dioxide-induced global warming was not the culprit for active hurricane seasons, Gray produced a chart that showed that in the 17-year period between 1948 and 1964, when there was a strong Atlantic Multi-decadal Oscillation and more tropical cyclone activity than occurred in the following 25-year period, carbon dioxide levels were actually lower. 

“Yes, CO2 maybe makes a little difference, but up or down, nobody knows,” he said. “It’s noise level. Anyone who says they know anything about it is lying to you. They may think they know, so they’re not honestly lying to you.” 

Having been born in 1929, Gray has been around long enough to see some temperature cycles and he says it is wrong for scientists today to keep extrapolating temperature increases as if they are going to continue happening. 

He noted that at different times, by extrapolation scientists have predicted the coming of new ice ages because of cooling trends and that people were worried about global warming in the 1940s because of a warming trend. 

“Everyone extrapolates warming and cooling trends,” he said. “It’s human nature to do that.” 

Gray showed a slide that pointed out that even increasing global temperatures have not corresponded with an increase in United States land-falling named storms, hurricanes or major hurricanes. In the 56-year period between 1900 and 1955, there were 213 named storms, 116 hurricanes and 45 major hurricanes that made landfall in the US. In the 56-year period that followed, in which the global temperature increased 0.4 degrees Centigrade, there were actually fewer named storms (182); hurricanes (88); and major hurricanes (34) that made landfall in the United States. 

Paying a price 

Gray did not argue that there is a general warming of the globe occurring now, but he sees it as more of a cyclical natural phenomenon rather than a man-made one.  

“These are natural changes and we can’t blame humans,” he said. “I’m not saying there aren’t environmental problems; we have all sorts of problems we have to deal with.” 

Gray said his main concern is that the perceived threat of global warming is changing the way industrialised countries get their energy, which in turn has made energy more expensive and has affected the standard of living of millions of people. 

Bucking mainstream science has cost Gray in the eyes of many of his peers and with the government.  

At the National Hurricane Conference in Orlando in 2010, Gray and Klotzbach’s seasonal hurricane forecast presentation was a part of the all-day general session in the main auditorium, which included some of the United State’s top hurricane officials. During his presentation that day, Gray was highly critical of those blaming increased Atlantic Basin hurricane activity on human-induced global warming, calling their theories “poppycock”.  

This year, Gray and Klotzbach weren’t invited to be a part of the general session at the National Hurricane Conference, but were relegated to a small conference room the following day. When dozens of conference attendees couldn’t squeeze in, the conference organisers scheduled a second session with the popular duo later that afternoon. 

His outspoken and controversial stance has also cost Gray and Colorado State University government research funding, Gray said. 

“Either you play ball or you don’t get funded.” 

Regardless, Gray plans to continue his campaign to identify salt and not carbon dioxide as the main driver of the current active hurricane period. 

“My goal is to save the world from global warming,” he said with a smile. “Whether I succeed or not, I don’t know.” 

“People confuse the multi-decadal changes in hurricanes with global warming. The main driver is salt, not CO2; they just got their chemicals wrong.” - William Gray