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Supercomputing and Climate Research
Mr. Obvious writes: "It must have already been submitted, since the article is over a day old (gasp!) but there's a good
round-up
on the state of the art in supercomputing, as it applies to modeling the weather --- that is to say, modeling the planet --- over at the NYTimes. They go into lots of interesting things concerning how hard it is, what progress has been made lately, why the US researchers feel themselves to be hamstringed in comparison to those in Europe or Japan, and even into some things you probably didn't know (I didn't, at least) about the weather."
As we now have good models for why CO2 should cause temperature change,
Do we? Those models aren't based on the greenhouse effect of CO2 (which is easy to predict, and which apparantly can't raise world temperatures by more than a fraction of a degree). They're based on an assumed positive feedback from the greenhouse effect of water vapor: the idea being that that fraction of a degree rise from CO2 will increase evaporation from the oceans, which will put more water vapor in the air to cause a *real* greenhouse effect.
Needless to say, this is a hard theory to quantify; hence the need for all the supercomputers.
but not the other way round,
And this is just wrong. Ever opened up a hot can of soda?
There are currently 720 billion tons of carbon in the air. Sound like a lot? It's nothing compared to the 39 trillion tons of carbon in the oceans. And when you heat up the oceans, what happens? Same thing as in your soda: the solubility of carbon dioxide changes, and CO2 is released into the air. If the temperature goes up, the ocean releases CO2. If the temperature goes down, the ocean absorbs it.
So which is happening? Do temperature changes cause CO2 level changes, or vice versa? Hell if I know. I used to believe the latter, now I'm leaning toward the former. The most convincing piece of evidence I've seen is a paper (published and presumably peer-reviewed by Science, although it's been quoted by quite a few more biased sources since then). Atmospheric CO2 Concentrations over the last Glacial Termination has another graph showing those scary CO2/temperature correlations over about 12000 years... but with some less scary conclusions. It seems in their ice cores, CO2 changes lagged temperature changes by 800+/-600 years.
Good thing Al "Earth in the Balance" Gore was saving the planet all his years in Congress and the White House by being driven everywhere in a 4 mile-per-gallon limo eh?
I suspect they know a hell of a lot more about nonlinear dynamics (including "chaos theory") than you do. For instance, turbulent flows are generally chaotic, making it impossible to predict the path of a given particle for more than a brief amount of time. On the other hand, the resultant mixing can be easy to study statistically on a larger scale, and it is entirely possible that the longer the model runs the more accurate the aggregate results. Stated differently, it is entirely possible (even likely) that a system that is divergent when modeled on a small scale is convergent when modeled on a large scale.
Climatological modelers were among the first to realize the implications of Lorentz's results. They, and most other scientists in fields involving nonlinear dynamics, have spent the last three decades digesting and incorporating both the results spawned by his discovery, and earlier "forgotten" results like those of Poincaré. That's not to say all climatologists have sufficient understanding of chaos, but the community as a whole has long been aware of it.
As to the politics of the situation: just follow the money -- as usual.
I am a physicist with a strong background in chaos theory and I am also one of the team who ported (but not yet optimized) the modified Boulder model on the NEC supercomputer in Lugano/Manno (not Bern, as incorrectly stated).
So yes, the effort is multidisciplinary and - at least in Switzerland - climatologists are well aware of the implications (many of them are physicists).
See <http://www.climate.unibe.ch> (I hope that NCCR/Climate gets a real website up and running soon) and <http://www.cscs.ch>
--
fB
The above statements are false. As someone who works for a weather company and hears a lot of theories, it still very much in question whether manmade greenhouse gasses are causing global warming.
Our current evidence suggests that increased surface temperatures are more likely caused by increased development (ie, asphalt) nearby ground measurement stations. Also, cyclical sunspot activity results in a curve of zipper-pattern fluctations in the radiated energy that reaches the earth over ~11 year period. The above two observations *do* have substantial physical evidence to back them up, and are a better explanation for recent global warming than the greenhouse theory.
It must have already been submitted, since the article is over a day old
/. editor. Even if it had been posted already today, it still wouldn't stop a /. editor from posting it again.
That won't stop a
--
--
"Outlook not so good." That magic 8-ball knows everything! I'll ask about Exchange Server next.
I haven't worked in this field for 5 years, but even then the computer models were fast enough to run the models several times with slightly different inputs. This is a standard technique to determine the sensitivity of the model to small errors in the initial values - classic chaos theory stuff.
What happens is you find the vast bulk of the model output is essentially the same. The variability is in the exact location of fronts, exactly the type of stuff that has always been difficult to predict.
Given a long enough time frame, everyone will fall under this uncertainty. So you still can't make long-term forecasts, but you *can* give decent 7-10 day forecasts if you have the flexibility to occasionally say that it's impossible to forecast the weather on some of those days. In the vast majority of cases that's good enough - it allows people to avoid scheduling activities when the weather is likely to be nasty.
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
Wow could you please give us a brief synopsis of your research papers which back up your theory. You must be published in science or other scientific journals if your research is that solid. I would love to read your articles and am curious to know where you got your meteorology degree and what your phd dissertation was on.
You must be a very well informed and regarded climatologists to be so absolutely sure of your facts like this I look forward to reading your articles and resume.
Thanks.
War is necrophilia.
The middle of last month (JUNE!) it snowed 14 inches bozeman montana.
War is necrophilia.
You would expect the vice president of the most powerful country in the world to be driven around in an escort?
Idiot.
War is necrophilia.
Care to present any of this evidence? I haven't heard of any natural processes which would significantly raise the amounts of greenhouse gases in the atmosphere over the last 50 years.
BTW, I though the debate was mainly about how the climate will change and how screwed we will be when it does. What caused it may make interesting research, but we aren't going to be able to stop it, whether it's anthropogenic or not.
OK. You are right.
And the National Academy of Sciences (US) report on global warming, drafted by the senior US scientists in the field, is wrong. As is every other major collaborative meta-analysis of existing evidence.
You point out that the EPA and UN-funded scientists have found evidence of global warming. Notice where their funding comes from. If Exxon was paying the bill, these same guys would no doubt have found the opposite. Government and industry researchers don't get tenure.
The UN didn't FUND the scientific research, only the report.
There actually is very little debate even on this topic anymore, either in the scientific community or in the VAST majority of world leaders (Dubya being an exception). The northern hemisphere is warming. Human generated gases are a principal cause. Even with climatic fluctuations, the changes in the last 50 years are ring clear as a bell. The situation is similar to that about 10 years ago, when everyone except the tobacco producers were claiming that nicotine was addictive. Well, guess what - it is the most addictive substance on the planet.
No one stands to make a tenth the money from global warming as the energy companies stand to make from selling energy. The bottom line is that there is really no way to get out of it without using clean energy or less energy. Clean energy costs more, and less energy stunts growth. Either way there are economic consequences.
But you have to think about the consequences of failing to act quickly enough. New Orleans is under sea level. So is Amsterdam. Virtually all the US east coast cities south of DC will be under water - places like Virginia Beach, Charleston, Savannah, Miami. And that pales in comparison to what will occur in low lying areas in Asia. (Note: so far Antarctic ice is unaffected. If it continues to be unaffected there will be no oceanic rise of note)
Besides that - entire ecosystems in the northern hemisphere are shifting climate so rapidly that native species do not have time to migrate further north. The amount of warming in the last 50 years can be translated to a shift in latitude. And in some areas, notably Alaska and Siberia, these shifts are killing native species.
I think if you do your research a little and read the works of the scientists who study climatic change, you would have very little doubt indeed about whether there is northern hemispheric warming or whether human generated gases are at least substantially to blame.
Actually that makes me wonder.
Does the Heisenburg (?) uncertainty principle apply at a macroscopic level ?
If we observe the weather, can we do so without modifying it ?
fwiw, i've always wanted to somehow work that into my defense whilst protesting a speeding ticket..
"boy, i clocked you doing 77mph back there"
"do you know which way i was going ?"
"yes"
"then you couldn't possibly have known how fast I was going"
My opinions are my own, and do not necessarily represent those of my employer.
My bluetooth SETI@HOME comment was really about the problem of data gathering. If people can buy a bluetooth weather station module and put it on their roof/in their garden/in the house we could see a huge increase in sampling. Yes we still need more sampling at higher levels, but it is about evolving greater sample spaces to match our increasing processing power. As a further response suggests we could make radical advances in the future with nanoprobe technology (resistence is futile). Either way I still believe the current "boundary" of predictability will be broken in my lifetime.
Never underestimate the dark side of the Source
You are a quiter! Simple as that! I fully expect to see major advances in weather prediction techniques in my life time (I suspect I have 25-100 years to go :-). Take Moores Law, the internet and human wisdom ... I have hope. Perhaps they will make a Bletooth devices that lets you contribute to the new SETI@HOME and monitor your local weather. Perhaps the Newtonian-Motzart of the digital age will come up with something way out there that leaps us forward. Chaos theory exists, however where is the threshold of understandability? Can we understand the system well enough to know where it is? Are we sure nothing will make a difference?
Never underestimate the dark side of the Source
The IPCC report is a sham. The scientific conclusions were ALTERED to match the political conclusions. This is a fact, which caused much crying of foul in the scientific community. "Nature" was caught in a hamstring over the scientific integrity of the report was questioned. Specifically, sections of the report which clearly stated that the models were imperfect and could not with any certainty predict future climate events were REMOVED from the report.
The current climate models are not even predictive - they can not even recreate past climate events, let alone predict future ones.
As to the report put in front of G. Bush, its an even bigger fraud. The scientists who signed the report DID NOT WRITE IT. It was written by functionaries. Several of the signees were global warming sceptics, who do not support anthropogenic climate change hypotheses.
Derek
...to blame it all of the damned butterflys...
Looking at the article:
0 3C LIM.html
http://archives.nytimes.com/2001/07/03/science/
I can see that they're standing beside many racks of SGI Origin 3000 gear (whether it's a single machine or many smaller machines depends on the cabled configuration -- O3K uses a mesh of cables rather than a backplane for its third-generation ccNUMA architecture).
At any rate, I'm curious as to who company they'll be buying their new system from. The only clue I can gather is their mention of 5120 CPUs to churn out 40 TFLOPS... that's 7.8 GFLOP per CPU which pretty much rules out SGI or even the latest Pentium/Xeon, Itanium, UltraSPARC III, or Alpha (unless one uses a very Apple-esq SIMD benchmark but I would imagine they want and need something more flexible for true performance with SISD, SIMD, and MIMD combined, rather than just bragging rights for a high single benchmark and top spot on Top500). My guess is they're going with either the not-yet-released Cray SV2 (which will combine the parallel strengths of the T3E with the vector strenghts of the SV1ex) or NEC's successor to the SX-5 (SX-5 is marketed by Cray in the USA, but under its creator, NEC, in other countries).
Anyone have additional insight?
Nobody had the technology in 1950, and I doubt we do now, to measure the temperature around the globe and get a global, annual average accurate to a tenth of a degree. Forget it.
e nces/Meteorology/Urban_Climate/
:)
:)
Three words, buddy: satellite remote sensing. You're right about one thing - we didn't have that technology back in the '50s. But starting with the TIROS satellites, that all changed. Currently, there exists a plethora of satellite sensing systems which not only measure temperature, but moisture content, cloud cover, and a whole slew of other relevant parameters, all with reasonable accuracy.
One other thing that bugs the crap out of me about "global warming". NOBODY EVER TALKS ABOUT CONCRETE, STEEL, AND ASPHALT!!! Hasn't ANYBODY ever noticed how hot a street or roof gets in the sun?!? I expect a few temperature measurements in growing cities would be more than enough to throw off their temperature measurements.
Try this on for size:
http://directory.google.com/Top/Science/Earth_Sci
Just because you're not listening doesn't mean we're not talking about it.
Greenland was green when it got its name, folks.
Actually, Leif Eriksson named the island "Greenland" because he thought people would want to move there if the island had an attractive name. Read "Greenlander's Saga" for more information.
Concidering that planktin, not rain-forests as the greenies would like you to think, fix something like 70-80% of the CO2 in the atmosphere, it would appear that the earth is more than capable of absorbing whatever increase in CO2 we're providing.
Care to post a reference? IANABiologist, but I would assume that water-borne plankton would absorb CO2 from the ocean - so the ocean (not the plankton) would have to provide the additional uptake of CO2 for the plankton to make a difference. But I could be wrong - I'm not really good with fish.
There are two things to consider when talking about the climate: one, that the climate has definitely warmed in the recent years. Two, we have yet to figure out why. Certainly climate models show the impact of CO2, but they're designed to do so. Other climate models use different, more natural phenomenon to produce the same warming. Essentially, if you want to say that "X causes global warming" it's possible to create a model that will indeed show that X causes global warming. Climate modelling is just too complicated to come up with a definitive answer. But, given the possible outcome of anthropogenic climate change, do we simply ignore the problem as a Chicken Little scenario, as you tritely suggest?
Buy my book! I just lost a fortune in tech stocks and I need money!
Hehehe...did you invest all your money in DrKoop.com?
But what does my opinion matter, I just vote here. It's not like I have any money or anything.
IBM has already been doing top notch work with the National Weather Service in forecasting. They worked with the NWS to develop a modeling system called Deep Thunder that could provide highly accurate predictions for a local area (25 miles or so). They apparently used it during the 1996 Olympic games in Atlanta to ensure that the closing ceremony would not get drenched. Read about Deep Thunder in this Wired article and on IBM's web site.
"sweet dreams are made of this..."
I think the moderators have demonstrated quite effectively the reality that modern weather/climate science is almost completely driven by the environmental extremists whose chief research tactic is to shout -- no scream -- down anybody who discovers something that doesn't fit into their neat little global warming agenda.
I'll start to believe the possibility of significant human contributions to global warming and the so-called greenhouse effect when I see intelligent discussions of viewpoints that disagree with the current wacko political agenda.
The first question I'd like to see addressed is how exactly the earth emerged from the last ice age without the assistance of the internal combustion engine.I was going to post anonymously, but then I got a grip and realized that all I'm going to suffer is the loss of a couple karma points on /. Like I could care.
The best diplomat I know is a fully activated phaser bank.
The best diplomat I know is a fully activated phaser bank.
-- Scotty.
actually, the first poster is entirely correct - although I cannot recall the equation of the uncertaintly principle it still holds true in the macroscopic world, it's just that the wave functions of macroscopic objects (ala schroedinger equation) are far greater than their associated uncertainty. The process of the police observing your speed does change your direction (solid objects also have wave functions, they are just far less significant than in elementary particles), but to such a small extent that it not appreciable:
The radar pulse interacts with the molecules of your car, imparting a small degree of energy coming in from a certain vector (like a gentle breeze) which does change the direction of the car but to such a small degree that it is totally undetectable, and only of mathematical curiosity.
-Nano.
IMHO, there is already a scientific consensus on both of the things you mention. An overwhelming majority of the climate scientists is convinced that we are responsible for the climate change. I believe that those few who disagree are industry lapdogs.
What we don't have is a political consensus on reducing the emissions. Scientists are not listened, especially when the right thing to do would be expensive and unpleasant. (I think GW Bush has not nominated a science advisor yet. If he has, please inform me.)
This has been due to high pressure systems from up North coming down South.
The other interesting thing is that insurance companies are now very wary of insuring many areas susceptible to tropical storms. FLorida actually had to force insurance companies to insure people who insist on building in dangerous areas. In Australia, there are now areas where insurance rates have gone up hundreds of %, and some areas just cannot get insurance.
In fact, Hurricane Andrew drained several billion dollars from Australian re-insurers and sent then broke, Not again!
Microsoft - Where would you like to go today, Maybe Jail?
That are significant in terms of the list. For example any that would even make it in the top 100? Ya, sure, I know of supercomputers that aren't in the list but they wouldn't even make it (much less rank high enough to make a difference). Now if you happen to know the location of a teraflop unit not on there than please, enlighten us.
It's warming right here in the USA. I don't need a scientist to tell me this; when I step outside the front door it feels hotter over the last 10 years.
10 years is not a geological timescale. On a true geological timescale, a century looks like an instant.
It's likely that 100 million years from now, the effects of the human race plotted against time are going to look indistinguishable from the effects of the comet that wiped out the dinasaurs. Given human nature, I doubt that there's even anything that can be done to avoid that.
At the very least, we all get to witness one of the biggest events in the earth's history, like being a passenger in a huge slow-motion train wreck.
(First, a preface. I'm a member of a computational astrophysics research group. We have ported our codes to the kinds of hybir d architectures of the machines discussed here, and have benchmarked their performances. Moreover, we have previously run on vector machines, so we have a fair idea of the pros and cons of the two approaches.)
While zavyman points out the basic problems inherent in parallelizing any discretized numerical model, the problem in obtaining good performance on hybrid architectures like the IBM SP-2s and SGI Origins which currently top out the top 500 list goes much deeper.
First, these machines are built around a hybrid architecture. Each node has a few processors (typically between 4 and 16, depending on the model), which utilize shared memory. These nodes connect to one another via an internode interconnect, with relatively modest bandwidth.
While this hybrid architecture allows supercomputer manufacturers like IBM and SGI to scale into the thousands of processors, it also introduces a substantial complexity into building of high-performance codes. Ideally, one would like to run threads-based parallelization on each node, and MPI between nodes, though the reality is that most codes in use use only MPI.
One can get decent scalability (into the hundreds of processors) when one runs physical models with limited communication -- ie, which simulate hyperbolic PDES like those of hydrodynamics (as zavyman describes above). However, things become more interesting when one considers more varied physics, such as that involved in solving elliptic PDEs (such as Poisson's equation for self-gravity or electrostatics). Because elliptic equations connect everything with everything else on the spatial domain, the communication costs ARE MUCH HIGHER. It is extremely challenging to build a multiphysics code with such varied parallelization demands. Indeed, it is a fair statement that no one has yet achieved excellent performance on anything close fo the thousands of processors available on these hybrid machines. For instance, another poster describes a climate model available from another research group. However, if you dig deeper, you find that they state,
"ForesightWX uses an IBM 12-node system with 52 processors working 24 hours a day. The cluster fits snuggly in a small room. A decade ago the same power would have filled the building."
52 processors is a far cry from the thousands of processors available to the users of these machines. Since each processor is slower than a vector processor like the Cray (by about a factor of 3 - 5), and assuming ideal speedup, such modest levels of parallelization lead to speedups of about 10-15 relative to a single Cray T90 processor. It is quite evident that there is little net gain over running the same simulation on 8-16 T90 nodes.
Moreover, due to the hardware constraints described above, IT MAY VERY WELL BE THE CASE WE NEVER SEE EXCELLENT MULTIPHYSICS PERFORMANCE ON THEM.
(One can get better parallel performance by increasing the problem size, but as the article points out, doubling the resolution of a simulation increases the cost by a factor of 16; hence, simply increasing the problem size may lead to unacceptably long computation times.)
I think massively parallel architectures will ultmately be the wave of the future, but there is little getting around the fact that the current generation of IBM-SP2s are dogs in the performance category.
Bob
Science, like Nature, must also be tamed, with a view turned towards its preservation.
This is a monte-carlo approach (hence the name Casino-21). Each machine will run a completely *independent* climate simulation with no interaction with anyone else's machine. The point being that each simulation is set of with a slightly different set of options on the "control dials" of the model. The big ensemble of results will then help scientists determine the sensitivity of the climate to different effects.
OK, Moore's law will solve a lot of the problems, but not all of them. One of the big problems is gathering input data! We have this huge system to model, and we only have datapoints every few hundred miles. The air column goes up 10s of thousands of feet. Even if the govt put a gound station on a grid of 10 miles on a side, you still have to send up weather ballons to get readings of the air column (Temp, humidity, winds aloft etc) all the way up.
So, there are HUGE holes in the data. Makes it hard to make a model
-- 73 de KG2V For the Children - RKBA! "You are what you do when it counts" - the Masso
This graph is one of the scariest things I have seen in a long time. It's a plot of the temperature variations and CO2 levels over the last 500,000 years measured from ice cores drilled out from Lake Vostok in the Antarctic. The two series track each other incredibly closely.
As we now have good models for why CO2 should cause temperature change, but not the other way round, it is something to take very seriously.
The figure was taken from The Economist magazine, a paper not usually associated with extreme anti-business views. Two recent articles gave good summaries of our present state of knowledge about global warming, and how both the data and the models have improved over the last ten years:
- The Reality of Global Warming (14 June 2001)
- The science and politics of global warming (16 Nov 2000)
(Titles given are those used in the magazine's index of its environmental stories online.)Article on the report for the Bush administration from the National Academy of Sciences.
Background piece before the last 'Kyoto' meeting in the Hague
One worrying new possibility is that there may be an abrupt change (bifurcation) in the ecosystem response as the temperature rises. At the moment about 50% of the manmade CO2 emissions are being absorbed by the Amazon rain forest. But the latest Hadley Centre models predict that if the temperature continues to rise, this greatly increases the frequency of much drier weather in this region, causing the forest to dry out, ultimately leading to uncontrollable forest fires. This would release vast amounts of more CO2 into the atmosphere if the whole lot went up -- perhaps ten times as much as human activities.
(And that is not the ultimate nightmare positive-feedback scenario, which is the enormous amounts of methane hydrate locked up at the bottom of the ocean in the arctic permafrost. The only thing that keeps it stable is the high pressure and low temperature. There is thought to have been a runaway destabilisation 55 million years ago, which raised the temperature 15 degrees C in less than 20 years).
I suppose somebody might come up with a techno-fix solution. But the complacency of gambling on that is like playing Russian roulette with five of the six chambers loaded.
I dount that the situation has changed remarkably since then. One thing that I'm sure hasn't changed is that there is no shortage of really solid data to support both sides: that the temperature really has risen, and that it really hasn't. There are thousands of temperature time series, some direct and some inferred, some are climbing, some are falling, and most aren't changing significantly after controlling for all the relevant sources of variance.
Globally it is likely that the 1990s was the warmest decade and 1998 the warmest year recorded (since 1861). Certainly this seems to be the case in the northern hemisphere not simply since 1861 but for the last ten centuries.
Yep, I hope so. We are still coming out of a little ice age, returning to the higher temperatures which were the norm when the Vikings grew grapes in Newfoundland. The scary thought is that we might find out, in 100 years, that the temperatures are really going down.
You point out that the EPA and UN-funded scientists have found evidence of global warming. Notice where their funding comes from. If Exxon was paying the bill, these same guys would no doubt have found the opposite. Government and industry researchers don't get tenure.
There are literally thousands of responsible scientists who work in these fields who believe that any sort of costly action to "avert global warming" is a bad, irresponsible idea. Some of them are Exxon employees, but certainly not all. Here and here (loosely related) are a couple of random links which might help make the point that it isn't a settled issue in the minds of people who understand it and aren't funded by the Government or Greenpeace (HINT: both these groups find it easier to get money from the public if they can claim that the sky is falling.)
In short, ad homenim arguments are less productive than usual here, since we see the usual suspects on each side of the issue. The energy companies are pushing their issue, Greenpeace is pushing theirs, and so on.
We need to consider the consequences of being wrong. Seeing the global temperature rise by 1 to 2 degrees C is probably going to make the world a better place to live in the long run. That's the maximum likelihood prediction from most of the models that folks on either side take seriously. The doomsday 5+degree C senarios have very low probabilities under most models.
Consider the cost of "taking action": Millions of people around the world, most of them already desperately poor, will die earlier and more miserably if we do anything to limit energy use. The only thing I can think of to reduce greenhouse gasses without causing disaster is replacing coal with nuclear power. That isn't going to happen anytime soon, unfortunately, because of the same agenda that is driving the "its getting hotter" side of the issue.
See what I've been reading.
I hate it when the press makes it sound like America is the jack-ass backwards donkey of the supercomputing world. This writer implies the Japanese and Europeans have vastly superior computing power. This is clearly the notion of a chucklehead. Take a look at The Top 500. By its (Linpack) metric, 8 of the top 10 machines are in America. Three of them are DEDICATED to weather or environmental work (Naval Oceanographic Office, National Centers for Environmental Prediction). A fourth one at NERSC is relatively open, compared to defense machines, and I'd be willing to bet weather code is running on it regularly. These are all teraflops machines. Japan has the other two in the top 10. Anybody know the job mix on those two? Europe's fastest machine is the Hitachi in Muenchen. The fastest dedicated European weather machiens are the T3Es at the Deutscher Wetterdienst and at the UK Meteorological Office.
I don't buy these whiny weathermen's complaints. The difference is that the American machines are all massively parallel machines (mostly IBM SP). The Japanese manufacturers all make vector machines, some of which the Europeans use. The Cray T3E is kind of a weird in-between architecture. It takes a good programmer to use a MPP to its full capability. The vector users, on the other hand, have 30 years of old code and practice which keeps them in the game. If the Americans would suck it up and learn to use their amazingly fast IBMs we would hear whining from the other side of both ponds. If you try to run your old code for the Cray C90 on an IBM SP, you are going to get terrible performance. If you rewrite the code, you may get great performance. But these guys aren't rewriting the code. Take for example the machines at NCEP. These create the daily production weather models used all over the US. They are IBMs which replaced a Cray that self-immolated about 1.5 years ago. When they brought the new machines up, I wonder if they rewrote the code beyond making it run? If you know, enlighten us!
- Kabauze
Nobody had the technology in 1950, and I doubt we do now, to measure the temperature around the globe and get a global, annual average accurate to a tenth of a degree. Forget it.
One other thing that bugs the crap out of me about "global warming". NOBODY EVER TALKS ABOUT CONCRETE, STEEL, AND ASPHALT!!! Hasn't ANYBODY ever noticed how hot a street or roof gets in the sun?!? I expect a few temperature measurements in growing cities would be more than enough to throw off their temperature measurements.
Then, there's the well-ignored fact that we're coming out of a mini ice-age, which peaked circa 1850. Greenland was green when it got its name, folks. The earth got colder since then and is warming back up, completely without our assistance.
And another thing... I saw just the other day that one of NASA's earth-monitoring has recorded a 30% increase in the levels of planktin in the oceans over the last 10 years. That's not a prediction, folks, that's a direct measurement. Concidering that planktin, not rain-forests as the greenies would like you to think, fix something like 70-80% of the CO2 in the atmosphere, it would appear that the earth is more than capable of absorbing whatever increase in CO2 we're providing.
Really, these global warming people sound about as rediculous as the Y2K people. The sky is falling! The sky is falling! Buy my book! I just lost a fortune in tech stocks and I need money!
If you're interested in lending a hand to such research into climate change, some folks at the Rutherford Appleton Laboratory would appreciate your help with their Casino-21 distributed client. Its still in the preparatory stages (ie client comming soon), and requires a significant investment in terms of commitment as compared to such things as SETI@home: "Casino-21 client will most likely require at least 128MB of memory, and 500MB of free disk space".
troodon.net
The article notes the objection of global warming skeptics as if there is scientific consensus that a) the build-up of so-called "greenhouses gases" causes the Greenhouse Effect (probably true) and b) that an increase in the concentration of greenhouse gases is anthropogenic (probably false):
Yes, the Earth is warming in some areas, e.g. Siberia. But, this is totally expected if you look on a geological timescale, vis-a-vis the Ice Age cycle. The debate is centered on whether or not man or natural processes (cycles of flora and fauna, volcanoes) are driving the current trend. I have not seen any convincing evidence to support the existence of anthropogenic phenomenon, and plenty to support the existence of natural phenomenon.
*** Proven iconoclast, aspiring epicurean ***
These crazy scientists are going to modify the weather pattern on Earth : as they progress in their weather simulations, they'll need more and more supercomputers, which in turn will run so hot they'll raise the temperature world-wide, which will make it harder for the scientists to simulate the weather, so they'll need more supercomputers ...etc... ARGHH, SOMEBODY STOP THEM !
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
If the Americans would suck it up and learn to use their amazingly fast IBMs we would hear whining from the other side of both ponds.
Great, what the hell do you think we are doing over at Argonne National Labs? I mean, have you tried to paralellize an atmospheric climate modeler? I don't think so. Coding for a vector-based machine is pretty straight forward. You concentrate on once machine as if it had one processor and one bank of memory, and code away, occasionally noting if your loops are not easily vectorized. The compiler magically does the rest, and your program runs really fast. That's why the Japanese machines are nice.
On the other hand, imagine designing an atmospheric climate modeler on a large cluster. The current paradigm being used and developed is MPI Let's see what you have to worry about. One, since the processors are not sharing memory, messages have to be passed between them to share memory. No biggie. But now consider that the whole atmosphere has to be broken up into pieces of a grid. On the boundaries, grid points must be shared by two or more processors. At each timestep, those points must be synchronized. Code must exist to know the processors that border one another and that know which points to share.
Now what happens if you want to combine different models together, as in the atmosphere, ocean, land, and sea-ice models. This is known as a climate coupler. Well, now you have differing grids for each of the models because they were developed independently. Now your program must handle interpolation of the grid points and must again know which processors border one another so that data is efficiently transfered. Finally, there must be decent load handling so that each processor is doing its fair share of the work.
I'm now working on the climate coupler project here at Argonne. Vector machines are quite easy to program, but we do know that they will lose out to massively parallelized clusters. It's just that the programming is much more difficult, since the messaging is always the bottle neck. Communications development follows a rate similar Moore's Law, but with a longer doubling time. For maximum efficiency, the programmer must handle the messaging model directly.
The modeling group here at Argonne understands the issue, and we are working on a general climate system to run quickly on parallized machines. No you know why you can't just do a simple code rewrite. You need to redesign the whole system.
Accelerated Climate Prediction Initiative.
as it applies to modeling the weather --- that is to say, modeling the planet
The article's a little misleading. It starts with a discussion of the weather, then moves on to discuss modelling of the climate. It's basically impossible to predict the weather -- meaning the exact temperature, rainfall, cloud cover, etc. -- more than a week in advance, because you have to specify the model with essentially infinite precision or chaotic effects take over. In fact weather prediction was one of the earliest manifestations of chaos theory. The climate -- meaning long term averages -- can exhibit stable behaviour that is possible to model in the long term. Don't look for this technology to dramatically improve weather prediction.
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