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« The Pause comes of age - Josh 295 | Main | Inner damage »
Wednesday
Oct012014

Climate models and clouds

Idly looking for something to write about this morning I sidled over to Geophysical Research Letters where my eye alighted on the abstract of a paper by Cheruy et al. It concerns the CMIP5 climate models and considers clouds and the transfer of moisture from land to atmosphere. Here's the abstract:

Over land, most state-of-the-art climate models contributing to Coupled Model Intercomparison Project Phase 5 (CMIP5) share a strong summertime warm bias in midlatitude areas, especially in regions where the coupling between soil moisture and atmosphere is effective. The most biased models overestimate solar incoming radiation, because of cloud deficit and have difficulty to sustain evaporation. These deficiencies are also involved in the spread of the summer temperature projections among models in the midlatitude; the models which simulate a higher-than-average warming overestimate the present climate net shortwave radiation which increases more-than-average in the future, in link with a decrease of cloudiness. They also show a higher-than-average reduction of evaporative fraction in areas with soil moisture-limited evaporation regimes. Over these areas, the most biased models in the present climate simulate a larger warming in response to climate change which is likely to be overestimated.

If I'm understanding this correctly, when you consider climate models' simulation of clouds and land-atmosphere coupling, the warmer models show the most marked biases against observations.

But don't worry, they are just fine and dandy for informing policymakers.

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Reader Comments (19)

Seems to me that if we want rid of this kind of sh*t we should get UKIP in. Roger Helmer said yesterday at Doncaster that UKIP will repeal the 2008 Climate Change Act.

http://rogerhelmermep.wordpress.com/

It won't work quite like that I suspect because UKIP likely won't get into a controlling state.

Oct 1, 2014 at 9:43 AM | Unregistered CommenterEx- expat Colin

Making a tentative return to blog-posting I have already noted a blogpost from Tamsin on communicating the uncertainties (which I believe Richard Betts also focusses on). Basically "communicating the uncertainties" boils down to accepting there are uncertainties, but they don't matter - probably most of us on this blog have, in their normal life and their work, had to make decisions not having all the facts. It is one of those things that normal people don't have a problem with. I should post the discussion later today, but in it Tamsin lays out what the scientists are certain of:

“The earth WILL continue to warm, rainfall WILL become heavier in many places (such as wet tropical regions), and sea level WILL continue to rise.” (my capitals).

My argument goes as follows:

In the days of more modesty in science, scientists would have prefaced such a statement with the cover all “All other things being equal…” But not today and certainly not in the clisci community, where there appears to be no uncertainty at all about their ability to foretell the future. Which is, well… a bit primitive

What makes a scientific theory plausible is that it is able to explain the past and foretell what will happen in future circumstances accurately. The most counterintuitive science in history, quantum mechanics, does this with immense success. The more the theory explains the physical world both past and future the more plausible it is.

I am not an expert either in climate science of computer modelling so can’t misrepresent the uncertainties, but simply point them out. Simply put there are about 1000 questions that could be asked about Tamsin’s statement above. Not unreasonably, the first one being why the CMIP5 models have consistently overestimated the temperature rise in their predictions. I can’t speak for everyone of course, but I think the inability to foretell future temperatures, surely the easiest of all the predictions, shows massive uncertainty in the model outputs.

Not getting the predictions right from the get-go suggests “all other things” aren’t equal, and that the uncertainties are really massive gaps in our knowledge, not minor issues that can be dealt with once we’ve dismantled the industrial power of the Western Industrial Civilisations.

Oct 1, 2014 at 9:45 AM | Unregistered Commentergeronimo

have always been fascinated byt how Climate models, like government social programs, defy evolutionary pressures and continue to exist despite uselessness.

Oct 1, 2014 at 9:45 AM | Unregistered CommenterDEEBEE

have always been fascinated byt how Climate models, like government social programs, defy evolutionary pressures and continue to exist despite uselessness.

Oct 1, 2014 at 9:45 AM | Unregistered CommenterDEEBEE


Once you start to view them as a form of ornamentation, then it starts to make more sense. A bit like a Peacock's tail.

Oct 1, 2014 at 9:53 AM | Unregistered Commentermichael hart

I should post the discussion later today, but in it Tamsin lays out what the scientists are certain of:

“The earth WILL continue to warm, rainfall WILL become heavier in many places (such as wet tropical regions), and sea level WILL continue to rise.” (my capitals).


Other than the rainfall (never looked at the data) what is there to disagree with when compared to the data over the last 200 years that we have. A simple natural recovery from the LIA gives you the same outcome except that at some point in the future there will be a drop in Temps and the sea rise will stop when the next LIA arrives, when that will be is unknown.

Hardly a support of CO2 induced warming and just shows how little is really known about the Earth's Climate despite the £BN's spent.

Oct 1, 2014 at 10:04 AM | Registered CommenterBreath of Fresh Air

In 1974, Lacis and Hansen introduced into GISS' Atmospheric Science Sagan's aerosol optical physics. It's present in the models as the ✓3(1-g) terms. It was wrong then and it's wrong now.

It claims that as optical depth increases, more scattered sunlight returns to Space; an asymptote to 1.0 hemispherical albedo; ludicrous. Real Mie scattering gives 0.5; there's a second process. Twomey knew it; his work was suppressed in 2004 to keep the 'Global Dimming' myth in AR4. Anyoine can look at ral clouds and work it out. Time for the truth to be accepted methinks.

Oct 1, 2014 at 10:17 AM | Unregistered Commenterturnedoutnice

Tamsin deceives, whether intentionally or not.
First, the stats on rainfall are anything but clear, and additionally, the fudge factor built into the 'prediction' is wide enough to turn a supertanker around in. So of what value is this prediction?
Second, the Earth has not continued to warm for 18 years now. Refusing to address that makes Tamsin look less than forthright. Additionally, in recent climate periods the Earth has warmed more than it did for longer than it did in the period just prior to the current hiatus. So again Tamsin makes a prediction that is meaningless.
Third, sea levels have been rising for well over 100 years, at about the same rate. Atolls are not drowning, coastlines are not sinking, lowlands are not being engulfed. Tamsin is consistently predicting nothing that has not been giong on for far longer than so-called global warming

Oct 1, 2014 at 10:35 AM | Unregistered Commenterhunter

The temporary correlation of atmospheric CO2 and temperature started almost two generations ago. Until then, climate science was a minor backwater as far as I can tell. There followed the rapid construction of the AGW scare, a huge increase in people working in the field and a big rush into modelling of the climate.

I am sure that in such circumstances methodical building of basic understanding went out of the window as the race went on to develop ever more complex GCMs. I really do wonder about the validity of the basic (and less basic) assumptions that underpin the science. The explosion in the number of people working in the field begs the question of how all these people were taught and the expertise of those doing the teaching.

it seems incredible that two decades after the alleged CO2 driven warming ceased climate scientists are starting to consider ocean oscillations, the behaviour of clouds and solar effects. It seems to me that not only are these absent in the models but they are not really understood at a basic level. The rush to work on CO2 driven warming seems to have excluded the basic understanding of many of the important drivers of our climate.

When I hear clever young climate scientists of the current generation spouting about their scientific convictions I do wonder about the quality of the science that they accept as fact.

Oct 1, 2014 at 10:38 AM | Unregistered CommenterSchrodinger's Cat

But WE all KNEW this - so why does it take climate scientists (I use the term loosely) take so long to come to these conclusions..?

Don't want to, perhaps..?

Oct 1, 2014 at 11:14 AM | Unregistered Commentersherlock1

So the models respond to high surface temperatures in mid-latitudes by reducing cloud cover in Summer. This is just positive cloud feedback.

The models suspend evaporation because the run out of surface water in sensitive areas of the same regions. This essentially turns cooling by evaporation into a positive feedback in these regions.

The use of global dimming is only a fix for the average surface temperatures of highly sensitive GCM's.

The use of positive feedback leaves its fingerprint in the model outputs by significantly reducing the rate at which heat loss from the surface increases with surface temperature. This in turn should increases the amplitudes of seasonal and (I strongly suspect) diurnal temperature variations predicted by highly sensitive GCM's. Is this what is been seen here?

The other effect of the positive feedback is that the highly sensitive GCM's should generate a slightly earlier maximum for summer temperatures. Is this true?

Oct 1, 2014 at 11:33 AM | Unregistered CommenterTrago 12

They also show a higher-than-average reduction of evaporative fraction in areas with soil moisture-limited evaporation regimes.

Do they mean ''deserts''?

Which is why deserts are hotter than rainforests. Basic physics

Oct 1, 2014 at 11:38 AM | Unregistered CommenterJohn Marshall

Geronimo / Bofa / hunter, Tamsin's blog post is a bit off-topic, why not comment there or chez moi?

The Cheruy et al paper starts off with


Most state-of-the-art climate models from the Coupled Model Intercomparison Project (CMIP) tend to overpredict the summer near-surface temperature at midlatitudes. It is the case for Regional Climate Model as well. Biases in the present-day simulations cast doubts on the reliability of the future climate projections, and question the use of near-surface variables produced by numerical climate models for climate change impact studies.

Oct 1, 2014 at 11:44 AM | Registered CommenterPaul Matthews

DB

"continue to exist despite uselessness"

Rather like Messrs. Gummer and Yeo. And Dave.

Oct 1, 2014 at 12:25 PM | Registered Commenterjamesp

Since

"most state-of-the-art climate models contributing to Coupled Model Intercomparison Project Phase 5 (CMIP5) share a strong summertime warm bias..."

Then,

"the models which simulate a higher-than-average warming..."

= "the worst models". Given just how badly we know the models perform on average, those ones must be seriously worst.

That's a curious fate that has a tendency to afflict people who start describing their models as "state of the art". Reality tends to find the art wanting.

Oct 1, 2014 at 1:15 PM | Unregistered Commentermichael hart

Climate Models: recycling GIGO (Garbage in, Grants out)

Oct 1, 2014 at 3:06 PM | Unregistered CommenterBernd Felsche

IPCC treats ALL the models it uses as having equal predictive validity, irrespective of past performance. There is no quality control based on conformance to reality.

Unless a model has been formally rejected by a peer reviewed study, it's as good as any other.

Oct 1, 2014 at 3:18 PM | Unregistered CommenterPolitical Junkie

The wisdom of peasants, who base their range of possibilities the natural world may come up with on a lifetime of careful observations, seems quite superior to the half-baked ideas of 'scientists' who have avoided careful observations like the plague.

Oct 1, 2014 at 11:24 PM | Unregistered CommenterAlexander K

At some time climate change was caused by warming (or cooling), but it was always the temperature that caused it.
"Over these areas, the most biased models in the present climate simulate a larger warming in response to climate change which is likely to be overestimated."

Now it seems to be reversed. Climate change gives warming!
The circle is now fully closed with a self fullfilling theory.

Oct 2, 2014 at 9:00 PM | Unregistered CommenterSvend Ferdinandsen

There are two issues here: (1) the global energy balance and (2) the local energy balance. The residual energy ( difference of solar short wave in and longwave (sigmaT4) out, Rn. varies diurnally and seasonally. Rn, in turn, is the sum of latent heat (LE, evaporation E) plus sensible heat (H), and soil heat flux (+/- G). LE and H are generally >95% Rn. The partitioning of the Rn-G into heating (H) and evaporation (LE) was studied in the 1920's by Bowen. In all terrestrial environments the partitioning of LE and H is primarily determined by the surface conductances to water and heat transfer, determined by a combination of surface stomatal conductance (gs) and aerodynamic conductances (ga). Given that ga is a fixed property of plant architecture (height, roughness etc), gs, surface stomatal conductance, is the prime determinant of LE flux and hence surface cooling.

Modelling the diurnal and seasonal variations of surface conductance is basically the key to modelling surface temperature change by biological mechanisms, and it is here that small changes in the modelling parameters can generate long-term cumulative soil water losses that change the H/LE ratio, and more Rn goes into heating (H).

Oct 3, 2014 at 2:12 PM | Registered Commenterdrjip

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