Showing posts with label katrina. Show all posts
Showing posts with label katrina. Show all posts

Monday, April 6, 2009

Atlantic Ocean Warming Dust Driven

This is a little unexpected. It is not unexpected that dust is a contributor but the magnitude certainly is. It appears that two thirds of the regional temperature gain can be attributed to dust and volcanic ash.

This also clarifies the feedback mechanism. We forget the heat gathering capacity of ocean water as compared to land because is attenuated through a thick upper layer. Land either absorbs and uses the energy chemically or reflects it back into the atmosphere. Thus the ocean has a stable temperature regime whose variation is minor as remarked on here. However a one degree rise represents a major jump in heat content in the water that will discharge into the atmosphere producing storms.

A modest amount of dust in the atmosphere generated major reduction in the driving heat engine.

The clear lesson is that a major volcanic interlude will be felt strongly in terms of climate change.

This returns me to contemplation on the possible causes of the worst climate experiences of the little ice age.
Assuming that we were on the low end of the normal Holocene climate variation, the injection of volcanic dust would have been rather damaging. And it need not be a overly big event. I recall that Fuji erupted in a timely manner and its position is such as to possibly affect European climate through high level aerosols and dust.

Thus provided that we already had a modest reduction is temperature due to a very slightly cooler sun, an inconvenient volcano could easily wreck a years climate while not even been noticed.

Dust Responsible for Most of Atlantic Warming

posted: 26 March 2009 02:15 pm ET

The warming of Atlantic Ocean waters in recent decades is largely due to declines in airborne dust from African deserts and lower volcanic emissions, a new study suggests.

Since 1980, the tropical North Atlantic has been warming by an average of a half-degree Fahrenheit (a quarter-degree Celsius) per decade.

While that number may sound small, it can translate to big impacts on hurricanes, which are
fueled by warm surface waters, said study team member Amato Evan of the University of Wisconsin-Madison. For example, the ocean temperature difference between 1994, a quiet hurricane year, and 2005's record-breaking year of storms (including Hurricane Katrina), was just 1 degree Fahrenheit.

Evan and his colleagues had previously shown that African dust and other airborne particles can suppress hurricane activity by reducing how much sunlight reaches the ocean and keeping the sea surface cool. Dusty years predict mild hurricane seasons, while years with low dust activity — including 2004 and 2005 — have been linked to stronger and more frequent storms.

In the new study, the researchers investigated the exact effect of dust and volcanic emissions on ocean temperatures. They combined satellite data of dust and other particles with existing climate models and calculated how much of the Atlantic warming observed during the last 26 years could be accounted for by simultaneous changes in African dust storms and tropical volcanic activity, primarily the eruptions of El Chichón in Mexico in 1982 and
Mount Pinatubo in the Philippines in 1991.

The results: More than two-thirds of this upward trend in recent decades can be attributed to changes in African dust storm and tropical volcano activity during that time.

This was a surprisingly large amount, Evan said.

The results, detailed in the March 27 issue of the journal Science, suggest that only about 30 percent of the observed Atlantic temperature increases are due to other factors, such as
a warming climate.

"This makes sense, because we don't really expect global warming to make the ocean [temperature] increase that fast," Evan said.

This adjustment brings the estimate of global warming's impact on the Atlantic more in line with the smaller degree of ocean warming seen elsewhere, such as the Pacific.

Of course, this doesn't discount the importance of global warming, Evan said, but indicates that newer climate models will need to include dust storms as a factor to accurately predict how ocean temperatures will change.

Satellite research of dust-storm activity is relatively young, and no one yet understands what drives dust variability from year to year. And volcanic eruptions are still relatively unpredictable.

"We don't really understand how dust is going to change in these climate projections, and changes in dust could have a really good effect or a really bad effect," Evan said.

More research and observations of the impact of dust will help answer that question.

Tuesday, October 16, 2007

Alex Hutchinson on stopping hurricanes

I read an article this weekend in the globe and mail by Alex Hutchinson who reported on several radical strategies for taming hurricanes. Most can be dismissed out of hand, although I am been perhaps a little unfair. On the other hand, we are really not that desperate to try most of them.

In any event, there has been a recent enthusiasm for linking global warming to a projected sharp increase in hurricane numbers. Of course the past two years gax been making nonsense out of that scheme.

What caught my eye though was his description of a deep water pump. This was an area that I had investigated a couple of decades ago with some interest. It had caught my imagination. The important statement however to me was that the transport pipe needed to be only 150 meters in length in order to have an effect on temperature.

The principal concept is to lift cold deeper water to the surface and using that to slightly lower the ambient temperature of the surface water. A very modest drop in surface temperature, around the equatorial waters of West Africa would kill the formation of hurricanes, which we all agree is a good thing.

There is one other major benefit not described. If the pipe goes deep enough, the water lifted will be mineral rich and will stimulate a a massive bloom of sea life down current. The mere fact of lifting enough cold water to create the appropriate temperature will in itself produce a massive fishery in what becomes the Gulf Stream.

Also not appreciated is that the problem of lifting the water is actually not a problem. Thanks to the difference in salinity there is a hydrostatic pressure difference between deep water and the surface that is positive. Certain enthusiasts even wanted to tap this as a source of power. The point is that if one can suspend a stiff walled pipe in the vertical position so that the inlet is a mile below the surface, it is fairly easy to give it a kick and start and maintain a strong flow to the surface. In fact it will come out as a strong jet at the surface.

The engineering problem then resolves to the problem of building long vertical straws that do not collapse and maintain neutral buoyancy. A large cross section is preferred to avoid very much friction. So our engineers need to make a make a long fat pipe, but perhaps not nearly so long as I anticipated twenty years ago. It would be tilted in the current and anchored to the sea bed with the top or outlet positioned a hundred feet below the ocean surface. Can we make it any simpler? When I was thinking about it I was trying to contemplate having a turbine taking energy out of the exit jet of a deep tube.

Instead, with much shorter tubes, we can tolerate a vastly lower exit velocity and no sub sea engineering. It is only a tube! We gain a control mechanism for the hurricane breeding grounds and a huge fishery linked directly to every tube emplacement that will surely pay for maintenance at least.

The question remaining is how to make the tubes themselves. There are many obvious and expensive methods available that could be used. Perhaps initially we will build a thin concrete shell on land with flotation chambers and then float it out to the anchorage. That may be good enough.

We do have one more tool in our bag of tricks. It is that it is feasible to grow calcium carbonate and manganese sulphate on a metal mesh by the application of a low direct current. This is exactly what shellfish do. Thus we can envisage continuously building a metal tube frame out of even low quality rebar and chicken wire and lowering it into the sea as fabricated with the direct current turned on. A mile long tube is no longer an impossibility if it is desired. It takes several months to fill in and it will become thicker and stronger as it matures. Of course flotation will have to be actively managed, but that will be true for any system.

A simple trick, a monster tropical fishery and no hurricanes or typhoons to wipe out our cities. Maybe it can actually work.