Recent Paper from Dr. Lindzen

[Richard S Courtney.]

ajmplanner:

You asked;

“A new paper from Dr. Lindzen and Dr. Choi appears to falsify some AGW claims through analysis of observational data.  The paper is quite technical, so if Dr. Courney or anyone else can transalte this paper into English for the rest of us, that would be helpful.  Thanks.  Link to the paper at

http://wattsupwiththat.com/2009/07/23/ne...m-lindzen/”

And I said I would try.  The following is my attempt.

The paper is titled
“On the determination of climate feedbacks from ERBE data”
is by Richard S. Lindzen and Yong-Sang Choi
and was revised on July 14, 2009 for publication to Geophysical Research Letters

Lindzen & Choi (hereafter refered to as L&C) analysed data from the ERBE experiment.

As brief explanation of the ERBE experiment I can do no better than to quote NASA at
http://asd-www.larc.nasa.gov/erbe/ASDerbe.html

It says there:

“The radiation budget represents the balance between incoming energy from the Sun and outgoing thermal (longwave) and reflected (shortwave) energy from the Earth. In the 1970's, NASA recognized the importance of improving our understanding of the radiation budget and its effects on the Earth's climate. Langley Research Center was charged with developing a new generation of instrumentation to make accurate regional and global measurements of the components of the radiation budget. The Goddard Space Flight Center built the Earth Radiation Budget Satellite (ERBS) on which the first ERBE instruments were launched by the Space Shuttle Challenger in 1984. ERBE instruments were also launched on two National Oceanic and Atmospheric Administration weather monitoring satellites, NOAA 9 and NOAA 10 in 1984 and 1986.”

Additional information on ERBE can be obtained by using the links in that URL.

The radiation budget is important because
(i)  If the Earth obtains more “incoming energy from the Sun” than the Earth emits to space as “outgoing thermal (longwave) and reflected (shortwave) energy” then the Earth will warm.
but
(ii) If the Earth obtains less “incoming energy from the Sun” than the Earth emits to space as “outgoing thermal (longwave) and reflected (shortwave) energy” then the Earth will cool.

(As an aside, it should be noted that warming or cooling need not mean change in temperature because it could take the forms of e.g. melting of ice or freezing of water at constant temperature).

Radiative forcing
is the change to the flux of radiation at the tropopause (i.e. the top of the troposphere which is the lowest layer of the atmosphere).

Climate sensitivity
is the degree of response of the climate system to a change in radiative forcing.  It is usually stated as an average change of global temperature for a change of radiative forcing equivalent to the change in radiative forcing from a doubling of atmospheric CO2 concentration. 

Feedback
Is a change to the climate sensitivity different from that expected purely from a change to the radiation budget.  Positive feedback provides more change to temperature than expected (i.e. high climate sensitivity).  And negative feedback provides less change to temperature than expected (i.e. low climate sensitivity).


So, L&C obtained the data provided by the ERBE experiment of
(a) incoming energy from the Sun to the Earth
and
(b) outgoing thermal (longwave) and reflected (shortwave) energy from the Earth to space.

They concentrated their studies on the data obtained from tropical regions of the Earth.  The bulk of solar radiation absorbed by the Earth is received in the tropics (which is why the tropics are hot).

And they found that
“for the entire tropics, the observed outgoing radiation fluxes increase with the increase in sea surface temperatures (SSTs).”

And they report
“The observed behavior of radiation fluxes implies negative feedback processes associated with relatively low climate sensitivity.”

In other words, they observed that in the tropics the sea surface warms LESS than could be expected from an increased heat input.  (The feedbacks are observed to be negative and this would tend to negate any warming).

This is important because, as L&C say,
“This is the opposite of the behavior of 11 atmospheric models forced by the same SSTs.”

In other words, the models say that in the tropics the sea surface warms MORE than expected from an increased heat input.  (The feedbacks suggested by the models are positive and this would tend to enhance any warming).

The reason for the observed negative feedbacks is not revealed by the L&C study, but they do explain the difference between what they observed and what the models suggest.  They say;
“Results also show, the feedback in ERBE is mostly from shortwave radiation while the feedback in the models is mostly from longwave radiation.”

Simply, L&C find the negative feedback is provided by reflected radiation and this suggests it is a result of changes to albedo (i.e. the reflectivity of the Earth) probably provided by changes to low level clouds. 

But the models suggest a positive feedback would be provided by radiation emitted from the Earth’s surface and from greenhouse gases in the air.

In reality, the positive and negative feedbacks probably both exist.  L&C find the net effect of the feedbacks is negative while the models suggest the net affect is positive.

Importantly, L&C suggest
“it is evident that, because the system attempts to restore equilibrium, there will be a tendency to underestimate negative feedbacks relative to positive feedbacks that are associated with longer response times.”

Put another way, L&C are saying that the negative feedbacks happen fast but the positive feedbacks occur over longer time.  So, observations over decadal time will clearly show the positive feedbacks but the negative feedbacks could be ‘overlooked’ to some degree because they do not occur over such long times (they will be intermittent ‘events’ within the measurement period).

Very importantly, L&C say
“ERBE data appear to demonstrate a climate sensitivity of about 0.5°C which is easily distinguished from sensitivities given by models.”

In other words, L&C say their analysis indicates that if atmospheric CO2 concentration were to double then global temperature would only increase by “about 0.5°C”:  this is much less than the rise of between 3.5 and 6 °C the models suggest for a doubling of CO2. 

However, their findings are from the tropical region and the feedbacks may differ at distances from the tropics.  Therefore, L&C say;
“Following Lindzen et al. [2001], allowing for sharing this tropical feedback with neutral higher latitudes could reduce the negative feedback factor by about a factor of two. This would lead to an equilibrium sensitivity that is 2/3 rather than 1/2 of the non-feedback value. This, of course, is still a small sensitivity.”

So, when the different feedback magnitudes of non-tropical regions are considered then it could be that L&C’s determination of climate sensitivity would double from “about 0.5°C” to about 1 °C for a doubling of atmospheric CO2 concentration.  But that is still much less than is suggested by the climate models.

The ERBE data is not capable of determining the mechanisms that provide the magnitudes of the feedbacks but L&C are now studying more recent data from CALIOP in an attempt to determine the mechanisms.

I hope the above ‘translation’ is clear and adequate.  Let me know if not.

Richard