Hurricanes, Monsoons, and SST anomalies

[Dogmudgeon]

I was initially going to post this in one of the threads relating to the unusually active Atlantic hurricane season, but I think it could sustain a thread all its own. Surface Seawater Temperature (SST) anomalies play a major role in climate prediction; according to an entire generation of oceanographers, starting with Wallace Broecker in the late 1960s, it is the changes in oceanic heat transfer (so-called "thermohaline circulation") that determine long-term climate.

When Global Warming phenomena are discussed, air temperature usually gets the spotlight. But climate is a combination of meteorological AND oceanological effects. The SST Anomaly provides a useful tool to help analyze weather and climate patterns.

This hurricane season is being driven by SST anomalies in the middle Atlantic Ocean that are about one degree Celsius (1.8F) above normal. And note that there is a pronounced "cold spot" off the Iberian coast. Passage through an area of cooler water off Eastern Florida may have weakened Hurricane Frances; hurricane Ivan, an unusually strong lower-latitude hurricane (Cat. 3, <5N latitude), may have been helped by warmer water in the South Carribean; and much of the favored area for generating tropical waves, off West Africa, is also warm for the season.


(NOTE: This chart automatically updates every 24 hours at midnight Universal Time -- 8PM Eastern/ 5PM Pacific Daylight time.)

I was unable to find data for the Atlantic ocean specifically, but this will give you an idea of how SST has has changed in the last 124 years:


(Above) Composite NOAA graphs of SST and surface air temperature anomalies. (Note the differences in scale among the charts.)

You can find a table of SST anomalies in degrees Farenheit at ftp://ftp.ncdc.noaa.gov/pub/data/anomalies/ocean_F.all (Jan 1880 - Jul 2004). Data modelers will be able to "play with" the data and make charts and graphs. Navigating the FTP directory will lead to many more data sets.

Just a cursory look at it will show something interesting: The last time the SST showed a negative (cool) anomaly was in September 1976 after three chilly years. That's 28 years ago this month. So, for the last 28 years, the ocean has been warmer than its mathematical average from 1880 onward. And this isn't even the warmest such period on record, as you can see from the chart above.

Again, keep in mind that the Seawater Surface Temperature (SST) anomaly data set is for the world-wide SST. Different parts of the Atlantic ocean may be warmer or cooler.

There is another major concern that SST anomaly charts address -- the Asian Monsoon. If you'll notice, it's been unusually cool in the area where the Monsoon forms. The Monsoon season is winding down now, but if this pattern persists, it could change the appearance of the Monsoon next spring -- then again, it might not -- such is the difficulty of predicting the weather! This is probably a more important impact than the impact of Atlantic hurricanes, since food production for approximately 2 billion people living in Asia is affected by the Monsoon.

Although the threats of rising ocean levels and a climate flip-flop to a new ice age are dramatic enough to have inspired movies (Waterworld and The Day After Tomorrow respectively), a radical increase in Atlantic hurricanes (and/or Pacific typhoons) or the disappearance of the Asian Monsoon would have disastrous effects all their own.

Weather prediction in general is notoriously imprecise. This hurricane season, we are seeing history-making deviations from the norm, but the rest of the season may be completely normal. Asian meteorologists have been trying to better predict monsoon behavior, since so much of South Asia depends on it. And climate change experts can tell you that the climate is, in fact, changing, but are still hesitant to make any specific predictions except that with the increase in heat, the weather will become less predictable. Next year, we may see a terrifying series of major hurricanes devastate the Atlantic coast, or nothing at all -- and probably, something in between. But the overall trend is probably toward larger, more powerful, more destructive storms.

I have a well-earned reputation for being an "optimistic pessimist." I think (with accumulating evidence) that the world's climate is shifting into a long-term return of the Ice Age (a "stadial era"), and that the dire warnings of "Peak Oil" are very likely to be justified. However, with forewarning and the application of a little intelligence and a little will, there is no need for the human race to be decimated and nature to be destroyed.

And, no -- I do not consider politics or economics to be acceptable reasons to abandon the Earth and Humanity to a die-off.

--bkl
As always: Corrections are invited.

[arcos]

1. very interesting...

thank you!

[Dogmudgeon]

2. A Better SST Anomaly map from the US Navy

As you can see, it allows better visualization of temperature anomalies, to the point where the developing El Nino is becoming visible, and especially the very large polar SST anomaly, which is implicated in abrupt climate change.

--bkl

[bemildred]

3. Shows why the Arctic is melting. nt

[NNadir]

4. Thanx for keeping us informed. Well done.