ENSO and climate

[oku]

Hi,

I currently have a discusion with a skeptic. I am trying to get the
point across that the radiation balance of the earth can only be
influenced by the three factors 1) solar radiation, 2) albedo and 3)
absorption of long wave radiation by the atmosphere (see here:
http://ipcc-wg1.ucar.edu/wg1/FAQ/wg1_faq-1.1.html). If we have high
average temperature during El Nino, and low during La Nina periods,
then this *seems* to contradict that. I understand that in El Nino,
warm ocean water releases heat to the atmosphere, and during a La Nina
the cold ocean water soaks up that heat. Since we measure surface
temperatures and not deep ocean temperatures, there is no
contradiction. Is that correct? Would it also be correct to conclude
that long term changes in ocean currents therefore cannot change the
average temperature of the earth (disregarding feedbacks), but just
local climates, because the amount of energy that can be released/
soaked up by the oceans is finite? (The guy I have the discussion with
seems to be a fan of William Gray)

Thanks,
Oliver

[Alastair]

El Nino involves a couple of other things. Clouds emit radiation to
the Earth and to space. So during an El Nino when there is cloud over
much of the Pacific the clouds cause warming. But I think the main
warming is from the release of heat stored in the ocean due to warm
water piled up against the East Indies by the Trade Winds. The IPCC
have not included exchange of heat with the ocean as a factor,
presumably because the exchange is always temporary.

Cheers, Alastair.

[Raymond Arritt]

Alastair wrote:
> The IPCC
> have not included exchange of heat with the ocean as a factor,
> presumably because the exchange is always temporary.

This is incorrect. The climate models referenced in AR4 are coupled
ocean-atmosphere GCMs, which include exchange of heat, mass and
momentum between the atmosphere and ocean.

Ray

[sploo.laroo]

I have often pondered this question about ENSO contributions to
interannual variations in global average temperature. I wonder if it
has been fully addressed in the literature, hence a reference to a
good paper on this would be helpful if someone has one.

Oliver mentions the ocean, and certainly this plays a part. In the
eastern tropical pacific, the typical condition has the oceanic
thermocline shallow enough that the trade winds driven upwelling draws
cool water from below the thermocline to the surface. During El Nino,
the thermocline dips and the cool sub-thermocline water is now too
deep for the upwelling to draw on. Thus, we typically think of "warm
water moving from the west pacific to the east pacific" during an El
Nino, but I think it is more accurate to say that the eastern pacific
warms while the west pacific stays about the same temperature, and the
warming of the east has more to do with vertical mixing in the ocean
than west-to-east mixing. So El Nino shuts down a process in the
eastern pacific that under non-El Nino conditions acts to cool the
atmosphere. This is certainly an important factor, but I've often
wondered if this is really sufficient to explain the global-scale warm
anomaly.

Oliver also mentions albedo and long-wave absorption. Given that
clouds impact both of these, and dramatic changes in tropical cloud
patterns accompany El Nino, I've always assumed that these changes in
clouds play a role in the global temperature anomaly. Alastair
mentions cloud-induced warming, but the cloud albedo contributes a
cooling that is comparable in magnitude to the warming from the cloud
greenhouse effect, so it may not be as simple as saying there are more
clouds. Someone must have looked at the changes in cloud radiative
forcing during El Nino. Anyone know of the paper?

Regarding "the amount of energy that can be released/soaked up by the
oceans is finite": that might be true, but we're a long way from
warming the deep ocean as much as it could be, and the time it takes
to mix thermal anomalies through the entire depth of the ocean is
millennial in scale. So by all means, changes in ocean currents that
alter the rate of vertical mixing of thermal energy in the ocean can
have profound impacts on the global average surface temperature.

-Eric

[Tom Adams]

On Apr 25, 4:34 pm, oku <oku...@gmail.com> wrote:

Here's theory that there is heat transfer out of the Pacific during El
Nino:

http://www.cnn.com/NATURE/9902/23/global.warming.enn/index.html

Seems be a theory to explain a single event in 1998. So the
correlation is theoretical right, not in evidence beyond the 1998
event?

[Alastair]

On Apr 28, 5:14 pm, Raymond Arritt <rwarr...@bruce.agron.iastate.edu>
wrote:

I was not criticising the IPCC climate models (although they are
wrong. :-)

I was trying to answer the question posed: Why do El Nino's cause
global warming?

The IPCC FAQ at http://ipcc-wg1.ucar.edu/wg1/FAQ/wg1_faq-1.1.html
says:

"There are three fundamental ways to change the radiation balance of
the Earth: 1) by changing the incoming solar radiation (e.g., by
changes in Earth’s orbit or in the Sun itself); 2) by changing the
fraction of solar radiation that is reflected (called ‘albedo’; e.g.,
by changes in cloud cover, atmospheric particles or vegetation); and
3) by altering the longwave radiation from Earth back towards space
(e.g., by changing greenhouse gas concentra­tions)."

Oliver wanted to know which of these three causes the warming during
an El Nino.

Because the IPCC are writing about radiation balance, they have
omitted the fourth factor involved in heat balance and that is input
to and output from ocean storage of heat. Of course that factor is
included in the ocean atmosphere coupled general circulation models
but it is not included in the FAQ.

It seems to me that during an El Nino the water collected in the Warm
Pool floods back over the Pacicfic Ocean. The surface then loses heat
as latent heat which rises, condenses, and radiates blackbody
radiation both upwards cooling the climate system, and downward
raising the surface air temperature giving the effect of warming the
planet. It cools and warms the planet at the same time!

It's an interesting problem.

Cheers, Alastair.

[Tom Adams]

"Average temperatures in areas such as California and France may drop
over the next 10 years, influenced by colder flows in the North
Atlantic, said a report today by the institution based in Kiel,
Germany. Temperatures worldwide may stabilize in the period."

http://www.bloomberg.com/apps/news?pid=20601087&sid=aU.evtnk6DPo&refer=worldwide

On Apr 25, 4:34 pm, oku <oku...@gmail.com> wrote:

[Raymond Arritt]

Tom Adams wrote:
> "Average temperatures in areas such as California and France may drop
> over the next 10 years, influenced by colder flows in the North
> Atlantic, said a report today by the institution based in Kiel,
> Germany. Temperatures worldwide may stabilize in the period."
>
> http://www.bloomberg.com/apps/news?pid=20601087&sid=aU.evtnk6DPo&refer=worldwide

They showed these results at the EGU meeting a couple of weeks ago.
When Keenlyside said that internal decadal variability could offset
expected warming over the next decade, I shuddered... certain people
will use the spurious break in the trend as an excuse to delay
addressing the long-term problem.

Ray

[Michael Tobis]

Indeed this would be a serious setback in the short term, inevitably. As James points out on his blog, it will also provide an interesting test of model fidelity. I think it will be of some use polemically if it verifies and of some use scientifically in either case.

Note that there is substantial decadal variability so such a hiatus is to be expected sooner or later. David Appell has a nice terse summary and an instructive graphic. http://davidappell.blogspot.com/2008/05/coming-global-cooling.html

As a sort of tarnished silver lining, if this pans out, when things bounce back people will overestimate the rate of warming yielding some overcompensation for imminent underestimation.

mt

[Tom Adams]

On May 1, 1:01 pm, "Michael Tobis" <mto...@gmail.com> wrote:
> Indeed this would be a serious setback in the short term, inevitably. As
> James points out on his blog, it will also provide an interesting test of
> model fidelity. I think it will be of some use polemically if it verifies
> and of some use scientifically in either case.
>
> Note that there is substantial decadal variability so such a hiatus is to be
> expected sooner or later. David Appell has a nice terse summary and an

> instructive graphic.http://davidappell.blogspot.com/2008/05/coming-global-cooling.html

>
> As a sort of tarnished silver lining, if this pans out, when things bounce
> back people will overestimate the rate of warming yielding some
> overcompensation for imminent underestimation.
>
> mt
>

> On 5/1/08, Raymond Arritt <rwarr...@bruce.agron.iastate.edu> wrote:
>
>
>
>
>
> > Tom Adams wrote:
> > > "Average temperatures in areas such as California and France may drop
> > > over the next 10 years, influenced by colder flows in the North
> > > Atlantic, said a report today by the institution based in Kiel,
> > > Germany. Temperatures worldwide may stabilize in the period."
>

> >http://www.bloomberg.com/apps/news?pid=20601087&sid=aU.evtnk6DPo&refe...

>
> > They showed these results at the EGU meeting a couple of weeks ago.
> > When Keenlyside said that internal decadal variability could offset
> > expected warming over the next decade, I shuddered... certain people
> > will use the spurious break in the trend as an excuse to delay
> > addressing the long-term problem.
>

> > Ray- Hide quoted text -
>
> - Show quoted text -

The Bloomberg article said "Temperatures worldwide may stabilize in
the period" the period being the next 10 years. Is that not what
the report said?

The article gives the impression that the oceans should be heating up
even if the global temperature is not going up. So is there some
other observation (other than global surface temperature) that will
show global warming even if 1998 remains as the record surface
temperature for 20 years?