Re: OT: is the AGW bubble about to burst?

In article <46C1895B.BF978147@xxxxxxxxxxx>, Eeyore wrote:

bill.sloman@xxxxxxxx wrote:

Eeyore wrote:
bill.slo...@xxxxxxxx wrote:
Eeyore wrote:
<EDIT FOR SPACE>
What's so miraculous about 28C ?

Google is your friend.

So, you admit you have no idea and simply took it on faith. As
presumably you've also done with all the other IPCC propaganda.

I don't know why precisely 28 degrees Celcius is magic - as opposed to
26.5C but I do know why there is a threshold.

28 degrees Celcius is magic because the energy that powers the
hurricane is the latent heat of evaporation in the humid air just
above the ocean surface. As this air rises and cools, the water vapour
condenses, releasing its latent heat slowing down the cooling and
driving the air to rise further.

If the temperature of the surface water is less than 28 degrees
Celcius, the process is stable. If the water is above 28 degrees
Celcius, the process runs away, eventually developing into a full-
fledged hurricane.

http://en.wikipedia.org/wiki/Hurricane

They regard 26.5C as magic for sustaining an established hurricane.

I couldn't be bothered churning this out at the time when I told you
that Google was your friend - you aren't exactly grateful for all the
education you are being exposed to, and very little of it seems to
stick, which doesn't encourage me to spend time spelling out what is
going on.

I strikes me that very little of the ocean can be that hot.

Have a look at current tropical Atlantic surface temperatures, in a map
from weather.com at:

http://www.weather.com/maps/news/julynonactive/
atlanticoceanseasurfacetemps_large.html

Looks like an area of the Atlantic Basin larger than the Continental USA
is currently 80-plus degrees F.

And the eastern half of the tropical Pacific at:

http://www.weather.com/maps/news/julynonactive/
pacificoceanseasurfacetemps_large.html

Looks like an area of the eastern half of the Pacific with about as much
area as North America has water surface temperature in the 80-plus degree
F range.

And Gulf/Carribean and nearby Atlantic with clearer numbers
(Fahrenheit), at:

http://www.weather.com/maps/news/julynonactive/
gulfcaribbeanseasurfacetemps_large.html

Currently all of the Gulf of Mexico has surface temp. 85-87 F, the
entire Carribean has surface temp. 83-87 F, and that map alone shows a
portion of Atlantic Ocean about the size of the Carribean at 83-plus F,
and some more Atlantic area having more area than the Gulf in the 80-82 F
range. The Gulf Stream is shown as having 80-plus degree F water to 38
degrees north latitude.

Hurricanes can form anywhere in these areas provided there is already a
thunderstorm triggering mechanism, sufficient lack of wind sheer, and
favorability for a low pressure area to form. If water surface
temperature gets into the upper 80's F, a thunderstorm cluster without
strong wind sheer can easily blow up into a major hurricane (but is far
from guaranteed to do so).

Hurricanes do form less very close to the equator, since they require
an air mass having angular momentum about an axis parallel to the earth's
axis.

As for the threshold water temperature: This will vary with air
temperature around the tropopause (and especially at average altitude
thereof). That is fairly constant in the tropics, and the air temperature
at the current altitude of the tropopause over the tropics is projected to
not warm as much as Earth's surface and surface-level-atmosphere is
projected to warm.
Lesser warming at tropopause level than at surface level is projected to
increase convection and that will actually hamper warming of the tropics
somewhat.

Another factor to consider is that the tropics will be warmed less by
global warming than most land areas and edge-of-sea-ice areas around 35-70
degrees from the equator because global warming reduces snow and ice
cover, causing increased absorption of sunlight. So if the globe warms by
1 degree as a whole, then Canada, the northern half of USA, some of
northern Europe, a big chunk of Siberia and sea-ice-edge areas would warm
a lot more than the globe as a whole, and the tropics would warm less than
the globe as a whole.

The tropics could warm to an extent only somewhat more than that
predicted by radiation balance alone by being more removed from a positive
feedback mechanism, and I do remember going to a website last year with an
online calculator and projecting by radiation balance that doubling CO2
content in the atmosphere would only warm the tropics by somewhere around
1 degree (I forget whether C or F). Extratropical areas would warm even
less if not for positive feedback from reduction of snow and ice cover.

So, global warming could cause only a minor worsening of number and
strength of hurricanes.

- Don Klipstein (don@xxxxxxxxx)
.

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