eirias | (no subject)

I've heard some speculation that global warming is the cause of the recent upswing in the number of major hurricane hits to the US. Apparently that's not the case. However, as common sense would suggest, it is possible that global warming will affect hurricane season in some way, and a recent article in Nature suggests that it already has, in that total power has increased over the last 30 years - but nevertheless the current/recent Atlantic activity, they say, is no more than one would expect from normal variation.

Further reading on hurricanes and on global warming in general for the curious (I'm looking at you,

upsilon! :) ). Some of them are pretty old at this point, but I tried to pick things in reputable journals.

Knutson TR, Tuleya RE, & Kurihara Y. (1998). "Simulated increase of hurricane intensities in a CO2-warmed climate." Science, 279: 1018-1020.
Harman JR, Harrington JA, & Cerveny RS. (1998). "Science, policy, and ethics: Balancing scientific and ethical values in environmental science." Annals of the Association of American Geographers, 88(2): 277-286. (This is a really great article!)
Nordhaus WD. (1993). "Reflections on the economics of climate change." Journal of Economic Perspectives, 7(4): 11-25.

Time to get my mind off the climate change train and on the getting to school on time train.

Flat | Top-Level Comments Only

Yeah, I feel bad for the people there, they had nothing to do with planning the city. However, it seems NO was built in an very ill advised place. Humans seem to think they can (and should) inhabit wherever they please, even if it's not the best idea (I'm looking at you Phoenix).

I'm assuming that NO will be rebuilt 'bigger, stronger, better' as if slightly better levies will prevent this from happening again.

Well, it's not as if anyone ever said, "Hey, I've got a great idea; let's build a large metropolis in this utterly disaster-prone location." Presumably, the town originally started there because, as the intersection between the continent's longest river and the ocean, it looked like a great trading spot. And then it grew because they were right. At what point do you say "Nope, too many people here, too dangerous, please stop growing"? Or, better yet, "Sorry, we've re-assessed the dangers, please 500,000 of you move 80 miles north now". Um, yeah.

So, I'm not saying it's a good idea. But I haven't the foggiest clue how you'd ever prevent such things from developing.

The disaster in NO was largely thanks to the US Army Corps of Engineers and their attempts to tame the Mississipi and Atchafalaya rivers over the past half century or so. NO is built on silt deposits that compact over time; these are layed down by the normal flooding activity. However, since we prefer not to have our major cities flooded every year, the levees were built to keep NO generally drier and less prone to floods. Great idea in theory, except that this prevents the floods from depositing more silt, so the land that the city is built upon just sinks instead of getting new earth to be on top of. Worse, the silt that would have been deposited all over the delta is instead deposited in the channel; this builds up (just like at the base of a dam), which displaces more and more of the water, meaning that you have to keep making your levee taller and taller, leading eventually to having a large amount of water suspended significantly higher than the inhabited land around it; this has the nice bonus of increasing the potential energy of anything that might happen to break through or spill over the top of your levee. Just like a dammed river will eventually cut a path through the dam, nature will eventually win and your levee will fail; this was pretty much an inevitable certainty without Katrina, but extreme weather conditions vastly accelerated the issue. The result is a new Atlantis.

But it's even worse than that -- NO is not going to be viable long-term anyway, because as the Corps of Engineers has attempted to tame Mother Nature in the Mississipi Delta, they have caused the Mississipi to change course; the river's new preferred course will take it quite a ways away from all of the economic infrastructure that depends on being at the mouth of the river. D'oh!

John McPhee's The Control of Nature (http://www.amazon.com/exec/obidos/tg/detail/-/0374522596/qid=1125598027/sr=1-1/ref=sr_1_1/103-2228170-9851029?v=glance&s=books) is strongly recommended reading and explains the situation much better than my little summary. (It's been about 12 years since I read it, so I'm a little fuzzy on some of the specifics.) In fact, all of his work is fairly excellent, from what I recall.

"Great idea in theory, except that this prevents the floods from depositing more silt, so the land that the city is built upon just sinks instead of getting new earth to be on top of."

Thanks for the explanation. I had been entirely missing that point, and wondering how it was even possible to build a city below sea level in the first place.... Looking at as a city that has sunk since it was built, suddenly it all makes sense.

Plus there's the joy of coastal erosion -- when the floods don't deposit fresh earth, the waters of the Gulf are free to eat away at the land... which of course diminishes the natural barrier between the sea and the city.