Tag Archives: GCM

General Circulation Models – Another Failure (by a factor of 10, possibly 100)

UPDATE: I guess it’s GENERAL CIRCULATION Models¬†(not “Global Climate Models”) and never again will I trust a journalist (when did I say that already… ūüėČ ) –

From MarsDaily (links added by me):

New analysis of data sent back by the SPICAM spectrometer on board ESA’s Mars Express spacecraft has revealed for the first time that the planet’s atmosphere is supersaturated with water vapour.

[…]¬†descriptions of the vertical distribution of water vapour – a key factor in the study of Mars’ hydrological cycle – has generally been based upon global climate models. This gap in the data has now been addressed by the SPICAM (Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars) imaging spectrometer on Mars Express.

[…]¬†Surprising new results [published in this week’s Science], based on SPICAM data obtained during the northern spring and summer, indicate that the vertical distribution of water vapour in the Martian atmosphere is very different from previous assumptions.

[…]¬†Until now, it was generally assumed that such supersaturation cannot exist in the cold Martian atmosphere: any water vapour in excess of saturation was expected to be converted immediately into ice. However, the SPICAM data have revealed that supersaturation occurs frequently in the middle atmosphere – at altitudes of up to 50 km above the surface – during the aphelion season, the period when Mars is near its farthest point from the Sun.

Extremely high levels of supersaturation were found on Mars, up to 10 times greater than those found on Earth. Clearly, there is much more water vapour in the upper Martian atmosphere than anyone ever imagined. It seems that previous models have greatly underestimated the quantities of water vapour at heights of 20-50 km, with as much as 10 to 100 times more water than expected at this altitude.¬†[…]

Kudos to RealClimate's Honesty and Sincerity

And no, I am not being sarcastic.

It’s just that (finally!) there is a RC claim that can be compared to the real world; next to it, a good dose of outright sincerity (surely it must have been there before,¬† perhaps buried in the polemic…)

From What the IPCC models really say (May 12, 2008):

  • Claims that GCMs project monotonic rises in temperature with increasing greenhouse gases are not valid. Natural variability does not disappear because there is a long term trend. The ensemble mean is monotonically increasing in the absence of large volcanoes, but this is the forced component of climate change, not a single realisation or anything that could happen in the real world.
  • […]
  • Over a twenty year period, you would be on stronger ground in arguing that a negative trend would be outside the 95% confidence limits of the expected trend (the one model run in the above ensemble suggests that would only happen ~2% of the time).

Note that even the fabled 20-year negative trend may still be interpreted as consistent with at least one model run.

But it’s a good step in the right direction: bringing back climate science from its forcings cage to the actual world…

Climate Models Are Irrelevant, and Latest IPCC Models a Regression

(many thanks to LM for pointing this out)

  • “[GCM] model outputs at annual and climatic (30‚Äźyear) scales are irrelevant with reality
  • model predictions are much poorer that an elementary prediction based on the time average
  • The GCM outputs of AR4, as compared to those of TAR, are a regression in terms of the elements of falsifiability they provide, because most of the AR4 scenarios refer only to the future, whereas TAR scenarios also included historical periods

Those are not the insane ramblings of yours truly, but the conclusions of D. Koutsoyiannis et al’s “Assessment of the reliability of climate predictions based on comparisons with historical time series“, a poster presentation at the European Geosciences Union General Assembly 2008 in Vienna, Austria, 13‚Äź18 April 2008.

Of course, it’s only a poster presentation…and of course, there was really no space at all to talk about it in the news, eg on the BBC.

Well, there is one good thing that has come out of this though: some¬†explicit references in RealClimate about the need to have “a very civilized and friendly chat, “to be respectful, sincere, and show courtesy in our criticism, even when we argue why we think that a paper has flaws“, and that “we some day may be mistaken, so it’s important to be humble and check our drafts amongst ourselves“.

This will mean no more verbal attacks about “negationism”, and few if any displays of condescension. Sure it will…¬†

Climate Change Detection/Attribution? Some Hope!

Curious situation on the website of the PCMDI – the “Program for Climate Model Diagnosis and Intercomparison”, at the Lawrence Livermore National Laboratory, with a stated mission:

to develop improved methods and tools for the diagnosis and intercomparison of general circulation models (GCMs) that simulate the global climate

Here’s what the PCMDI has to say about “devising robust statistical methods for climate-change detection/attribution“:

Coming soon…

That’s it.

Wow.

Sure.

Well, it looks like we will just have to be patient. We will be told how to detect and attribute climate change…one day, perhaps after some considerable amount of time will have ben spent in the frankly rather wasteful efforts of mostly comparing climate models to each other, rather than to the actual world.

p.s.: Applause to the PCMDI for their frankness:

The need for innovative analysis of GCM climate simulations is apparent, as increasingly more complex models are developed, while the disagreements among these simulations and relative to climate observations remain significant and poorly understood. The nature and causes of these disagreements must be accounted for in a systematic fashion in order to confidently use GCMs for simulation of putative global climate change.