I posed a question on the blog of Stu Ostro, senior meteorologist at
The Weather Channel, asking whether El Nino causes GW. See the El Nino
blog he http://tinyurl.com/lwyb6

We'll see if this politically charged hot potato is handled by TWC.

I suspect they will decline to answer. Better safe than sorry, after
all TWC is in the business of advertising, not necessarily explaining
science or answering weather questions.

But we might be pleasantly surprised. A safe answer, and
uncontroversial, would be a simple "no". But I would like to know
Stu's thoughts.

I'll check this blog in a few days and report back.

RL

Here is what the El Nino blog on TWC looks like as of today:

http://tinyurl.com/lwyb6

Yesterday was the day I always dread. It comes along every couple or
few years: the official pronunciamento that El Nino Is Here (this time
coming, by the way, just six days after the most recent update which
indicated otherwise).

Invariably, an announcement about the arrival of El Nino (or La Nina)
triggers the obligatory media onslaught. News articles yesterday
declared that El Nino is "an extreme warming of equatorial waters in
the Pacific Ocean that wreaks havoc with world weather conditions."
Fortunately, everything from pestilence to locusts hasn't been
attributed to this El Nino ... yet.

I was asked only semi-seriously by a producer if TWC could air within
its story on El Nino this 1997 Saturday Night Live clip. I responded,
somewhat to her surprise, that, as long as we had legal rights to
rebroadcast it, "Absolutely we should!" In it, Chris Farley brilliantly
personifies what to this day El Nino is made out to be. You may have
seen it on TWC last night or today.

Don't get me wrong, El Nino is an important and influential factor upon
the world's weather, but it is also a phenomenon that is often
misunderstood, and a term that lends itself to misuse and
sensationalism.

Let's take a look at what the deal really is with El Nino.


WHAT EL NINO IS

-A climate phenomenon that influences weather patterns. It specifically
refers to above-average sea surface temperatures (SSTs) in the central
and eastern equatorial Pacific Ocean.

-The opposite of El Nino (below-average SSTs in that portion of the
Pacific) is known as La Nina. When SSTs are near average, that is
called the "neutral phase."

-El Nino and La Nina are related to both SST changes and the natural
ebb and flow of trade winds across the tropical Pacific. The associated
fluctuation in atmospheric pressure is known as the Southern
Oscillation. The whole oceanic/atmospheric process is known as ENSO (El
Nino/Southern Oscillation).


WHAT EL NINO IS NOT

-A storm. A flood. A drought. A hurricane. A weather event or pattern.
(At times when its influence is particularly strong, such as when a
very active southern jet stream and storm track are present during
winter, that is sometimes referred to as an "El Nino pattern," El Nino
being a descriptor of the related, predominant weather pattern. However
El Nino itself is not a weather pattern per se.)

-Abnormal or bizarre. Both El Nino and La Nina are a natural part of
our world, and have likely been so for many thousands of years.

-The sole cause of individual weather events or the sole influence upon
seasonal weather patterns. (The water/land/atmosphere/sun climate
"system" is very complex.)

-Something that necessarily increases the amount of weather and climate
calamities. There are certain locations that do typically experience
specific kinds of impacts such as drought or flooding, but plenty of
extremes and disasters of all kinds occur around the world when El Nino
is not present. El Nino just tends to shift them around.


WHAT EL NINO DOES

-El Nino has a direct effect upon the atmosphere over the tropical
Pacific.

-It has an indirect influence upon weather patterns in other parts of
the world, including in and near the United States.

-The degree of this influence at any given time and place depends in
part on El Nino's intensity, which can vary, and on other weather and
climate factors.


Okay, now that we've established the basics, what about a few current
topics: myth or reality?


HURRICANE SEASON

As noted by me in an entry earlier in the summer, and by much more
formal studies such as this one which in turn references others, El
Nino tends to be an inhibiting factor when it comes to hurricanes in
the Atlantic basin.

Therefore is El Nino, which although formally announced this week has
been coming on for awhile, squashing this season in the Atlantic basin?

Well, if it is, then I ask: was El Nino, which also developed during
the 2004 hurricane season, responsible for Charley, Frances, Ivan, and
Jeanne? In fact, NOAA made the 2004 announcement about El Nino at the
exact same time (second week in September) as this year!

Why wasn't that season quiet? Because El Nino is just one factor that
goes into determining what happens during hurricane season. Although
it's an easy scapegoat, to what extent it's responsible for this
"quiet" 2006 season is open to question.

It's ironic (or, more aptly, symbolic?) that Gordon strengthened
significantly and became the Atlantic season's first major hurricane on
the same date that El Nino was designated as having developed.


A side note regarding this Atlantic hurricane season's alleged
inactivity: We're currently at three hurricanes and one major
hurricane, which is close to the long-term prorated average up through
this point in the season, and the eight named storms is actually three
above average.

It's just that the strongest ones so far -- Florence and Gordon, and
perhaps eventually Helene if it can overcome its disorganization --
have developed way out at sea and the current pattern favors
"recurvature" before reaching the Caribbean and North America. Turns
out that most of those which developed far to the east in 2004 and 2005
also went out to sea, and most of the bad ones which hit the U.S. the
past two years developed in the Gulf, Caribbean, and subtropical
Atlantic not far from land.

We'll have to see how many develop during the remainder of this season
and where they go, but remember that compared to 2005, most hurricane
seasons are "quiet" ... and I suspect that those who suffered damage to
their property or loss of loved ones due to Ernesto (perhaps as well as
folks in Bermuda) wouldn't consider this season to be quiet enough.


Side note #2: In the eastern Pacific, meanwhile, with Hurricane John's
remnants having soaked parts of New Mexico and Texas earlier this month
and Tropical Storm Lane now creeping north near Mexico, if one looks at
the historical record there's an interesting correlation between El
Nino and effects of tropical cyclones in the southwest U.S.


WINTER

With all the other proclamations has come this one: El Nino means a
mild winter, including for the northeast U.S. But does it? Well, maybe,
but not necessarily.

It is true that typically, above-average temperatures are predominant
across the northern tier of states in El Nino winters and especially
during moderate to strong ones. A warmer-than-average winter in, say,
the Northern Plains is a pretty good bet when El Nino is present, or
for that matter even when it's not these days due to the trend toward
warmer winters in the U.S. and elsewhere.

But ... the El Nino winter of 2002-03 was a memorably cold and snowy
one in the Northeast. And speaking of snow: here, to pick a place (the
biggest city in the country), are the snow totals during the four most
recent El Nino winters in the Big Apple:

Look at the extreme variation! One might expect the dearth in 1997-98
because that El Nino was exceptionally strong, but during all of the
other winters El Nino was weak or moderate. Once again, there are
additional factors at play that go into determining the outcome, such
as the NAO.

Other locations, for example Denver, experience a high degree of
snowfall variability during El Nino winters as well.


CALIFORNIA

Last but not least, the image which perhaps most prominently comes to
mind as soon as the "El Nino Is Here" headlines hit is that of storms
whacking California.

Is El Nino's reputation in California deserved? Yes and no. There does
tend to be a lot of storms coming into the state from the Pacific
during El Nino winters, and there's a pretty solid link between El Nino
and above-average winter precipitation, especially in Southern
California during strong El Ninos. The potent El Nino back in 1982-83
got a lot of people's attention, including that of scientists.

However, there have been El Nino winters in which central and northern
California have been drier than average, and in general the state has
not been hit equally hard during every El Nino. The amount of flooding
and storm damage depends on a number of factors, and many intense storm
systems and severe floods have also hit California while El Nino was
not present.

Although not updated recently, Jan Null has a great page which lays out
the reality when it comes to California flood disasters, as well as
this California/ENSO rainfall analysis and this piece on El Nino myths
in California.


THE BOTTOM LINE

While there can be some consistent and predictable attributes, all El
Ninos and La Ninas are not created equal, and the details of their
effects -- whether upon the Atlantic hurricane season, winter snowfall
and temperatures, or rainfall in California -- are not the same each
time.