Wild et al. [2001], a blue-chip study, shows that the downward longwave radiation in cold, dry climates is dramatically under-estimated in the GCMs used in IPCC TAR, as shown in the following excerpt from their Figure 4 (from one of the best GCMs). The bias is systemic.
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FIG. 4. Annual cycles of model-calculated and observed DLR (W m22) at some of the most reliable high-latitude sites, midlatitude sites, and low-latitude sites (see Table 1 for more information on these sites): model calculations by ECHAM3 (dotted) and ECHAM4 (dashed), and observed (solid). MARTIN WILD, ATSUMU OHMURA, AND HANS GILGEN, JEAN-JACQUES MORCRETTE, ANTHONY SLINGO, 2001, Evaluation of Downward Longwave Radiation in General Circulation Models, Journal of Climate 14.
Abstract: The longwave radiation emitted by the atmosphere toward the surface [downward longwave radiation (DLR)] is a crucial factor in the exchange of energy between the earth surface and the atmosphere and in the context of radiation-induced climate change. Accurate modeling of this quantity is therefore a fundamental prerequisite for a reliable simulation and projection of the surface climate in coupled general circulation models (GCM). DLR climatologies calculated in a number of GCMs and in a model in assimilation mode (reanalysis) are analyzed using newly available data from 45 worldwide distributed observation sites of the Global Energy Balance Archive (GEBA) and the Baseline Surface Radiation Network (BSRN). It is shown that substantial biases are present in the GCM-calculated DLR climatologies, with the GCMs typically underestimating the DLR (estimated here to be approximately 344 W m22 globally). The biases are, however, not geographically homogeneous, but depend systematically on the prevailing atmospheric conditions. The DLR is significantly underestimated particularly at observation sites with cold and dry climates and thus little DLR emission. This underestimation gradually diminishes toward sites with more moderate climates; at sites with warm or humid atmospheric conditions and strong DLR emission, the GCM-calculated DLR is in better agreement with the observations or even overestimates them. This is equivalent to creating an excessively strong meridional gradient of DLR in the GCMs.The very same tendencies are independently found in stand-alone calculations with the GCM radiation codes in isolation, using observed atmospheric profiles of temperature and humidity for cloud-free conditions as input to the radiation schemes. A significant underestimation of DLR is calculated by the radiation schemes when driven with clear-sky atmospheric profiles of temperature and humidity representative for cold and dry climates, whereas the DLR is no longer underestimated by the radiation schemes with prescribed clear-sky profiles representative for a hot and humid atmosphere. This suggests that the biases in the GCM-calculated DLR climatologies are predominantly induced by problems in the simulated emission of the cloud-free atmosphere. The same biases are also found in the DLR fluxes calculated by the European Centre for Medium-Range Weather Forecasts (ECMWF) model in assimilation mode (reanalysis), in which the biases in the atmospheric thermal and humidity structure are minimized. This gives further support that the biases in the DLR are not primarily due to errors in the model-predicted atmospheric temperature and humidity profiles that enter the radiative transfer calculations, but rather are due to the radiation schemes themselves. A particular problem in these schemes is the accurate simulation of the thermal emission from the cold, dry, cloud-free atmosphere.
Climate Audit 
16 Comments
As a bystander comment, shouldn’t the GCMs be most accurate in cold, dry, cloudless atmospheres and less accurate with the issues of cloudiness and evaporation?
Also,
Does this mean that the expectations of the programmers in modelling radiative forcing are causing this problem?
Perhaps the errors are due to incorrect humidity profiles as discussed here:
http://www.co2andclimate.org/climate/previous_issues/vol8/v8n12/hot1.htm
The humidity above 10 km is underestimated substantially. Using the incorrect low humidity values would lead to an underestimation of the LW radiation in the GCMs and an overestimation of the SW radiation at the surface in the GCMs. Both of these biases have been observed in the models.
Perhaps even more alarming for the modelers is that it means the water vapor feedback cannot be very effective since the upper atmosphere is already saturated with water vapor. That would mean that about 1.5 C of the warming in typical models is erroneous.
This paper to be published is perhaps somewhat related.
Good posting Greg. The paper certainly sounds good. Actual observations over a relatively short time using a consistent set of instruments that only need short term stability instead of long term stability and correlation to other esoteric stuff.
Sounds like indisputable proof that the current models need a lot of work and are useless in their present condition for any kind of useful predictions.
A single, reproducable, observable fact that does not fit a theory/model is all it takes to disprove the theory/model. It is really too bad that so many prominent climate “scientists” have forgotten/ignored this simple axiom of real science.
Let’s keep ’em coming people.
Here’s a link to the Douglass & Knox paper that Greg pointed out:
Click to access 2004GL022119.pdf
Re: #5
Excellent.
Wow … thanks a lot Chas. I just read through it quickly and this, I believe, will prove to be a very important paper. They used a volcanic eruption to measure impulse response of the atmosphere. Anybody who has any experience with signal processing (DSP) will understand the implications of this paper. (The U of R has a pretty good EE department … hmmmm).
Here is another observation – changes in the earth’s albedo – that climate models do not take into account.
http://www.sciencemag.org/cgi/content/full/304/5675/1299?ijkey=HhdOjAJ0NDCDc&keytype=ref&siteid=sci
If they stand up to scrutiny, these observations will also have major implications.
Here’s a link to the earth-albedo paper that Micheal Mayson pointed out:
Click to access pal04.pdf
I’ve just tried a(Beta)Google search page http://scholar.google.com
It looks as if it might be pretty good at tracking down copies of papers.
Thanks Chas – I got to the Science site and the paper ( without having to log in) from here http://www.bbso.njit.edu/~epb/papers.html. There are some other interesting papers as well.
Michael it is curious how sometimes one seems to get to the full paper via a link to a journal,though the bbso link didnt do it for me this time. (BTW the link needs its last full stop removing).
Many thanks for pointing to the paper! It does look to be exceptionally important.
-There is a second (public)collection of interesting .pdfs on the site at: http://solar.njit.edu/publications.htm
incl a recent cloud:cosmic ray study 🙂
Chas – amongst those papers at http://solar.njit.edu/publications.htm is this one
“The Earthshine Project: Update on Photometric and Spectroscopic Measurements”
whihc comments:
“Our simulations suggest a surface average
forcing at the top of the atmosphere, coming only from
changes in the albedo from 1994/1995 to 1999/2001, of
2.7-1.4 W/m2 (Palle et al., 2003), while observations
give 7.5-2.4 W/m2. The Intergovernmental Panel on
Climate Change (IPCC, 1995) argues for a comparably
sized 2.4 W/m2 increase in forcing, which is attributed to
greenhouse gas forcing since 1850.
Still, whether the Earth’s reflectance varies with the
solar cycle is a matter of controversy, but regardless of
its origin, if it were real, such a change in the net sunlight
reaching the Earth would be very significant for the
climate system.”
and
“Traditionally the Earth’s albedo has been considered
as a roughly invariant parameter in global circulation
models and climate studies. With the earthshine project,
we have shown how, on the contrary, the Earth’s albedo
is quite a variable parameter for which a detailed study
of its seasonality, long-term variability and climate implications
need to be carefully undertaken, if we are to
fully understand the present changes in the Earth’s climate.”
!!! Micheal, I dont know if you post at RC, but it would be interesting to read what Gavin makes of these two. The ‘Water Vapour’ commenting looks open.
If your post is rejected/deleted then they are probably very significant 😉
Chas – I did post this at Real Climate but they appear to not know much about it – which I find disturbing – see http://www.realclimate.org/index.php?p=119#comments.
Nice post- Though sadly Rasmus seems to have confused the nightly values of Fig.2 with the annual means of Fig.3
They didnt seem to have come across De Laat and Maurellis’s industrial CO2:temperature trends work either.
I don’t know how this is incorporated in the models:
A parametrisation of ocean albedo which is depending on wind speed.
Click to access albcontour.pdf
Jin, Z., T. Charlock, W. Smith Jr., and K. Rutledge, 2004: A parameterization of ocean surface albedo. Geophys. Res. Let., 31, L22301, doi:10.1029/2004GL021180.
Click to access jingrl04.pdf
http://snowdog.larc.nasa.gov/jin/getocnlut.html