Is it possible the increase in destructive hurricanes during the last few years could be the result of the early stages of global warming? The Germans are asking that question in this article in Der Spiegel.
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Whether or not we are experiencing irreversible global warming is a matter of conjecture. Whether or not we are experiencing one of the countless variations in global temperature which has occurred over the history of our planet is also conjecture, but, in my opinion, a more likely explanation.
I first gave consideration to the so-called greenhouse gases when I started teaching chemical engineering at a university in Australia and was looking at the implications of process plant design and the impacts of technology - around 40 years ago. I learned at that time that the output of oxides of sulphur and nitrogen generated by industry were dwarfed by the output of nature by way of geothermal activity. I also learned - through bitter experience - that the presence of water vapour in an atmosphere confounded the measurement of the concentration of the oxides of carbon because water vapour absorbs infra-red energy in the same wavelengths as carbon dioxide and carbon monoxide. Why, therefore, I thought, would a small increase in the amount of carbon dioxide increase the amount of energy absorbed by the atmosphere when there is a thousand or more times the amount of water vapour in the atmosphere? Further, if the temperature of the atmosphere rises surely evaporation at the surface of the oceans will increase and, most likely, increase the cloud cover, thereby increasing the planet’s albedo which will reflect energy back into space.
I find the comment of Emanuel that our perception of how bad a hurricane such as Katrina is dependent on the amount of destruction it causes - not the frequency or the intensity of such hurricanes. Some will recall that the northern Australian city of Darwin was, literally, flattened by a tropical cyclone (hurricane to you northern hemisphere, Atlantic constrained people!) named Tracey at Christmas in 1974. With my family, I was in England at the time and friends asked if our home (which was then Melbourne, Australia) would have been in danger. I had to point out that Darwin was as far from Melbourne as London is from, say, Athens.
However, what is important about this is that the central pressure of cyclone Tracey was measured at 960 mbar. Exactly two months later (give or take a day) we were in Dampier, in the north of Western Australia, when cyclone Trixie bowled straight over the top of us. The central pressure of Trixie was 950 mbar - 10 mbar lower than that of cyclone Tracey. I do not know what this means in terms of relative destructive power, but cyclone Trixie never made headlines because, at that time, the total population of the Pilbara region of Western Australia was only a few thousand. Wind velocities in excess of 155 mph were recorded in Dampier and at Hammersley Station, a few miles down the coast where Trixie finally crossed and headed inland, the anemometer was broken and stuck on 165 mph. There was significant damage in Dampier and other places, but no loss of life, and, therefore, no media interest.
I have not seen much physical information on Katrina, so I cannot compare it with Tracey or Trixie. Darwin was vulnerable to such a storm because of the building technology used 30 years ago. Dampier was also vulnerable, but to a lesser extent because the houses and other buildings had been designed for storm conditions to 130 mph. Darwin was a typical city - with all the loose rubbish around that becomes lethal projectiles in high wind conditions. Dampier was a company town that was closely controlled. By the time Trixie hit us (and the eye passed over us) the town had been cleaned of all loose rubbish, every person was indoors with cyclone protection screens over all windows, and nobody was allowed out until a written clearance was handed to them when the storm had passed.
These are events of 30 years ago which highlight, more than anything, that while there hasn’t been much change in the destructive power of nature, neither has there been much change in the readiness and ability of civil defence organisations to cope with such disasters.
And we are worried about global warming?
Comment by Gary Kerkin — September 4, 2005 @ 9:06 pm
I certainly agree that we cannot extrapolate from one or two storms a trend. And, your point about the differences in destructive power is well taken. A ten millibar difference with a low population area makes a different emotional impression. As I am not scientifically educated, I cannot debate the scientific arguments you use except to say that the correlation between greenhouse gas increases as measured in Arctic and Antarctic ice, for example, and the relatively sharp increase in temperatures in the last century and a half makes one want more information. Normally, these changes occur over much longer periods. However, I will concede your points about the problems of measuring CO2 levels accurately as I must rely on others understanding of such things. Thank you SO MUCH however for contributing!!!
Comment by Administrator — September 16, 2005 @ 2:01 pm