Co2 Is, And Has Always Been, The Biggest Climate Control Knob In The Earth’S History

[PersianPaladin]

CO2 is the biggest control climate knob. And it has been the biggest knob as far back as we can tell. So says Richard Alley. Actually it isn't so much him saying this, as the latest science. Richard Alley is merely summarizing the science

He concludes by thoroughly debunking the continuously repeated denier talking point that CO2 cannot cause global warming because in the paleoclimate record indicates that temperature lags CO2 :

But what do we say to people who say the lag proves current warming isn't caused by CO2? We know that orbital changes (the

Milankovitch cycles

) kick off the ice ages – this was predicted 50 years before we had data (in the 1970s) to back it up. But temperature never goes far without the CO2, and vice versa, but sometimes one lags the other by about 2 centuries. And a big problem with the Milankovich cycles is that they only explain a small part of the temperature changes. The rest is when CO2 changes kick in. Alley offered the following analogy: credit card interest lags debt. By the denialist logic, because interest lags debt, then I never have to worry about interest and the credit card company can never get me. However, a simple numerical model demonstrates that interest is the bigger cause of debt (even though it lags!!). So, it's basic physics. The orbits initially kick off the warming, but the release of CO2 then kicks in and drives it.

So, CO2 explains almost all the historical temperature change. What's left? Solar irradiance changes, volcanic changes. When these things change, we do see the change in the temperature record. For solar changes, there clearly aren't many, and they act lik a fine tuning knob, rather than a major control. 40,000 years ago the magnetic field almost stopped (it weakened to about

10% of its current level

), letting in huge amounts of cosmic rays, but the climate ignored it. Hence, we know cosmic rays are at best a fine tuning knob. Volcanic activity is important, but essentially random ("if volcanoes could get organised, they could rule the world" – luckily they aren't organised). Occasionally several volcanoes erupting together makes a bigger change, but again a rare event. Space dust hasn't changed much over time and there isn't much of it (Alley's deadpan delivery of this line raised a chuckle from the audience).

So, what about

climate sensitivity

(i.e. the amount of temperature change for each doubling of CO2)? Sensitivity from models matches the record well (approx 3°C per doubling of CO2). Recently,

Royer et al

conducted an interesting experiment, calculating equilibrium climate sensitivity from models, and then comparing with the proxy records, to demonstrate that climate sensitivity has been consistent over the last 420 million years. Hence paleoclimate says that the more extreme claims about sensitivity (especially those claiming very low levels) must be wrong.

In contrast, if CO2 doesn't warm, then we have to explain why the physicists are stupid, and then we still have no other explanation for the observations.

If there is a problem, it is that occasionally the world seems a little more sensitive to CO2 than the models say. There are lots of possible fine-tuning knobs that might explain these – and lots of current research looking into it.

Oh, and this is a global story not a regional one; there are lots of local effects on regional climate.

Note that most of these recent discoveries haven't percolated to the IPCC yet – much of this emerged in the last few years since the last IPCC report was produced. The current science says that CO2 is the most important driver of climate throughout the earth's history…

What I found fascinating about the talk was the way that Alley brought together multiple lines of evidence, and showed how our knowledge is built up from a variety of sources. Science really is fascinating when presented like this.

Rest of the article and the video presentation is here: -

http://mind.ofdan.ca/?p=2771

Edited January 25, 2010 by PersianPaladin

[Essan]

Hate to say it because I admire and respect Alley. But I think he's wrong. It's just not as simple as that.

[PersianPaladin]

Hate to say it because I admire and respect Alley. But I think he's wrong. It's just not as simple as that.

If you watch the talk; its anything but simple. He talks about the interactions in more detail. The passage I quoted was a basic summary.

[Gray-Wolf]

My pal down in Antarctica, Dr G., has this to add;

http://moregrumbinescience.blogspot.com/2010/01/co2-and-temperature-for-800000-years.html

[PersianPaladin]

My pal down in Antarctica, Dr G., has this to add;

http://moregrumbines...0000-years.html

Interesting.

My own humble (non-qualified) opinion is that AGW has sufficient credibility behind it to warrant risk mitigation NOW. It doesn't mean that our method of risk mitigation has to correllate with the way governments often like to exploit crises.

[Gray-Wolf]

Interesting.

My own humble (non-qualified) opinion is that AGW has sufficient credibility behind it to warrant risk mitigation NOW. It doesn't mean that our method of risk mitigation has to correlate with the way governments often like to exploit crises.

Fully behind you there P.P., far too warped when first the local politicians and then big Govt decided to "Go Green" (as used to be). They are not ,were not and will never be the answer. Mainly because it'd take longer than 4 yrs and that's all they plan for.

I'm also sick of the Co2 follows temp thang, they (Temp/CO2) are linked and when one moves the other follows. It's always been that way, will always be that way.

[PersianPaladin]

Fully behind you there P.P., far too warped when first the local politicians and then big Govt decided to "Go Green" (as used to be). They are not ,were not and will never be the answer. Mainly because it'd take longer than 4 yrs and that's all they plan for.

I'm also sick of the Co2 follows temp thang, they (Temp/CO2) are linked and when one moves the other follows. It's always been that way, will always be that way.

Yup. Also be VERY AWARE of the "green economy" bubble. There are only a few good solutions out there, and they are all (rightly) focused on de-centralised local permaculture and biogas generation for sustainable usage.

Edited January 26, 2010 by PersianPaladin

[SleepyJean]

I have a question. If the Milankovitch Cycles cause initial warming which causes a release of oceanic co2 which in turn increases and drives further warming, what is it that causes the temperature to decline prior to the fall in co2? The Milankovitch Cycle? If this is the case, where are we in the Milankovitch Cycle? When can we expect the earth to start to return to its normal temperature zone (ie an ice age?) And is co2 higher now than it has ever been? (which looks like 300ppm, but has any possible "loss of data" been taken into account on these graphs - degradation of the gas samples in the ice cores for example. We are talking about 400,000 years, after all).

I realise these are probably very basic questions, but I read the reports above and while I had never seen it in quite that way before it still has questions for me. If you could point me to websites or papers that can answer them that would be great.

Thankyou,

SJ

[SleepyJean]

Right, just been reading all about Milankovitch cycles. I think I've forgotten it already Erm, we are in a nearly circular orbit at the minute, but this is on the "outwards" phase and will become increasingly elliptical (with increasing difference between summer and winter temperatures). We are about halfway on axial tilt (the up and down of the equator?) and the angle is getting lower, so this is decreasing the difference between summer and winter temperatures? And axial precession means that at present the southern hemisphere has a bigger difference between summer and winter temperatures than the northern hemisphere does.

So we are about halfway between ice ages at the minute, with no hint that the atmosphere should be cooling! Are we just before or just after the warmest point of the cycle? I would guess that we are just after the warmest point, but that these processes are long term so any reduction on temperatures on the basis of these particular cycles would be on a minute scale measurable possibly only over decades or even centuries.

However, the ice core and paleogeological records would seem to indicate that the current warmth of the planet is something that only ever lasts a few thousand years and that the majority of the time the planet is much cooler (although not always technically in an ice age)? Looking at the Vostok ice core graphs, the temperature (global?) is only above 0 for a maximum of about 15,000 years at a time and is below 0 for around 100,000 years at a time.

At present we have been mostly above 0 for about 15,000 years now and so we might expect to be starting to cool. According to the modern temperature record we are not cooling but in fact still warming. So this is the basis of global warming theory, perhaps?

Right, so that is where it is for me, if I have understood correctly. I haven't even looked at co2 or any other factors yet, just the very basics. One thing that does stand out to me, though, looking at the graphs, is that the wave of the graphs seems to increase in size with each cycle, generally speaking (obviously it has some variation but the general pattern is for longer, deeper waves) So there is the possibility that the increased length of this warm phase is within the "norm". But I would be looking at the fact that a return to lower temperatures tends to be relatively abrupt, just as the initial warming does. So if we are responsible for the warming things could theoretically just get hotter and hotter, but if the earth has in-built safety mechanisms (or this is naturally a longer cycle), we could find ourselves in a fairly abrupt cooling situation. So we need contingency plans for either situation and it all starts and ends with alternative fuel sources that don't involve bio-fuels.

And it still doesn't explain why the global temperature cools ahead of the reduction in co2...

[sunny starry skies]

Right, just been reading all about Milankovitch cycles. I think I've forgotten it already Erm, we are in a nearly circular orbit at the minute, but this is on the "outwards" phase and will become increasingly elliptical (with increasing difference between summer and winter temperatures). We are about halfway on axial tilt (the up and down of the equator?) and the angle is getting lower, so this is decreasing the difference between summer and winter temperatures? And axial precession means that at present the southern hemisphere has a bigger difference between summer and winter temperatures than the northern hemisphere does.

So we are about halfway between ice ages at the minute, with no hint that the atmosphere should be cooling! Are we just before or just after the warmest point of the cycle? I would guess that we are just after the warmest point, but that these processes are long term so any reduction on temperatures on the basis of these particular cycles would be on a minute scale measurable possibly only over decades or even centuries.

However, the ice core and paleogeological records would seem to indicate that the current warmth of the planet is something that only ever lasts a few thousand years and that the majority of the time the planet is much cooler (although not always technically in an ice age)? Looking at the Vostok ice core graphs, the temperature (global?) is only above 0 for a maximum of about 15,000 years at a time and is below 0 for around 100,000 years at a time.

At present we have been mostly above 0 for about 15,000 years now and so we might expect to be starting to cool. According to the modern temperature record we are not cooling but in fact still warming. So this is the basis of global warming theory, perhaps?

Right, so that is where it is for me, if I have understood correctly. I haven't even looked at co2 or any other factors yet, just the very basics. One thing that does stand out to me, though, looking at the graphs, is that the wave of the graphs seems to increase in size with each cycle, generally speaking (obviously it has some variation but the general pattern is for longer, deeper waves) So there is the possibility that the increased length of this warm phase is within the "norm". But I would be looking at the fact that a return to lower temperatures tends to be relatively abrupt, just as the initial warming does. So if we are responsible for the warming things could theoretically just get hotter and hotter, but if the earth has in-built safety mechanisms (or this is naturally a longer cycle), we could find ourselves in a fairly abrupt cooling situation. So we need contingency plans for either situation and it all starts and ends with alternative fuel sources that don't involve bio-fuels.

And it still doesn't explain why the global temperature cools ahead of the reduction in co2...

Hi SJ, I'll have a quick go at this. So far as I understand it, you trigger deglaciations or glaciations primarily through orbital forcing. They both work in the same manner, in that you have an initial forcing, which generally measured as an insolation maximum (deglaciation) or minimum (glaciation onset) at 65 degrees N. In the case of deglaciation, the initial insolation push is then enhanced by a feedback with CO2 (from oceans?), and further enhanced by feedbacks from collapsing an ice sheet. But the insolation 'push' does not last, and so the system is able to come to an equilibrium when there is no further deglaciation and CO2 levels equilibrate to their new level. Conversely, an insolation minimum of sufficient magnitude will push the system back out of equilibrium, as it's enough to reduce temperatures, allow absorption of CO2 back into ocean reservoirs, and initiate the regrowth of ice sheets. These processes then feed back on each other, and if you're lucky (or unlucky as the case may be) you have a maturely glaciated world again... until the insolation 'push' is enough to trigger deglaciation. This is much simplified and does not account for the dynamical effects such as the Dansgaard-Oeschger events (perhaps triggered by ice dynamics, or binge-purge cycles).

So I think the thing is to get away from the concept that feedbacks always lead to a 'runaway' scenario in either direction. The feedbacks with our current global configuration are enough to naturally produce slightly warmer-than-present temperatures, and significantly cooler-than-present, but we know that the world has been up to 10C warmer than present in the past, with much more CO2 in the atmosphere.

So a couple of things: We've just passed a 65 deg N insolation minimum (presently perihelion is in early January), and yet the world is not cooling as expected. And, as G-W points out very neatly, CO2 and temperature on Earth have always (in geological time) been intimately linked. Where one leads, the other follows...

sss

[Admiral_Bobski]

...but we know that the world has been up to 10C warmer than present in the past, with much more CO2 in the atmosphere.

We also know that it has been as cool as present (if not colder) with a lot more CO2 in the atmosphere, and we know that it has been a lot warmer with as little (or only fractionally more) CO2 in the atmosphere:

CB

Edited February 10, 2010 by Captain_Bobski

[Optimus Prime]

"...but we know that the world has been up to 10C warmer than present in the past, with much more CO2 in the atmosphere."

If that's the case then we need to start considering whether our actions are having a bigger impact then first thought.

[Devonian]

We also know that it has been as cool as present (if not colder) with a lot more CO2 in the atmosphere, and we know that it has been a lot warmer with as little (or only fractionally more) CO2 in the atmosphere:

CB

Good answers here, basically yes CO2 has a major effect on climate but not just CO2 (btw, the most relevant part from 6/7 minutes into the video).

So CO2 can, if it's concentration changes, both have a major effect but other things can as well. For example the configuration of the continents has a big effect on climate, as do change to solar output and orbital changes and other geological processes. However, big slugs of CO2 don't come along very often.

Btw, the author of this video is a geologist.

Edited February 10, 2010 by Devonian

[Cycles]

I have a question concerning the distribution of CO2 around the earth.

We know official instrument readings are taken on Mauna Loa in Hawaii, at about 11,000 feet (about 3,200m). The current concentratons of 385 ppm are used as the official figure. However when reconstructing atmospheric concentrations through ice core samples, the sites are in the Antarctic and very high latitudes in the northern hemisphere, and not at 11,000 feet as in Hawaii.

This brings a question about science saying concentrations have never been as high as 385 ppm. First of all...the ice core samples are at high latitudes. Second..they are nearer sea level and not at 11 thousand feet. Third, they are taken from ice cores and not today's instantaneous instruments. Fourth..do we have readings at 11 thousand feet near the ice core sample stations? And/or what are the readings in the free air near these stations?

Regards

David Dilley

[Essan]

We know that CO2 levels are higher today that at any time in the recent geological past by looking leaf stomata. These are used to absorb CO2 - and in the process transpire H2O. Ideally plants would like to transpire as little as possible. Numerous studies have shown that because of this, the higher the CO2, the less stomata leaves have - ie in higher concentrations they need less stomata to absorb the required CO2.

Comparison of modern leaves and those from numerous collections around the world (actual preserved leaves and fossils) show they have less stomata today, from which we can reasonably deduce that CO2 levels are also higher today.

(Not ever having been so interested in biology, I only learnt this recently from reading David Beerling's The Emerald Planet)

In any case, CO2 levels are also measured in Antarctica. For example, at Jubany

[sunny starry skies]

Clarification on CO2 levels here, with a nifty video showing how the levels vary with latitude. You can see how the South Pole sites varies least (being farthest from emissions), but that all sites steadily rise to the 380ppm mark. At the end of the animation you see the connection in with the Siple Dome ice core CO2 record.

http://www.skeptical...uncertainty.htm

The data is from the World Data Centre for Greenhouse Gases:

http://gaw.kishou.go...dcgg/wdcgg.html

So that comfortably answers your questions 1, 3 and 4 David.

As for elevation, well that is rather easier to deal with:

Firstly, the top of the ice sheets (depending on which dome you're talking about) are over 3000m.a.s.l. Vostok station is about 3500m, or 11,500 feet above sea level. Greenland Summit (GRIP, GISP2) is 10,500ft. Other core sites are lower, but it is immaterial, because the concentration of CO2 is vertically fairly constant (within ~10ppm) throughout the troposphere, with a drop as you cross into the stratosphere of about 7ppm.

Therefore your question 2 is answered on two counts, first that the long ice cores are (coincidentally) at a similar elevation to Mauna Loa (please tell me you didn't think the ice sheets were flat and at sea level???), and secondly that the air is well-mixed vertically and so measurements at sea level are not that different to those higher up in the troposphere.

Bischof et al (1980) in Nature: http://www.nature.co...s/288347a0.html

Good slides showing vertical mixing esp slides 14-18, the values are rarely more than 5-10ppm through the air column:

http://www.tiimes.uc..._eol_070418.pdf

sss

Edited March 11, 2010 by sunny starry skies

[Cycles]

SSS

Very good post with good links. Looks like you pretty much answered my question. I of course still have concern over why earth's temperatures dropped and remained steady from 1940 into about the 1980s..this of course during a period when CO2 was steadily going up.

Thank you SSS, most informative

Regards

David

[sunny starry skies]

SSS

Very good post with good links. Looks like you pretty much answered my question. I of course still have concern over why earth's temperatures dropped and remained steady from 1940 into about the 1980s..this of course during a period when CO2 was steadily going up.

Thank you SSS, most informative

Regards

David

The short answer is anthropogenic aerosols, but I'll leave you to look up the IPCC AR4, to read and understand why temperatures don't always dutifully follow CO2 rise, as I've done enough research on your behalf. There'll be links on Skeptical Science too, which debunk most of the common denier arguments.

sss

[Cycles]

The short answer is anthropogenic aerosols, but I'll leave you to look up the IPCC AR4, to read and understand why temperatures don't always dutifully follow CO2 rise, as I've done enough research on your behalf. There'll be links on Skeptical Science too, which debunk most of the common denier arguments.

sss

Yes I understand the IPCC thinking, and of course Natural Cycles which are much more powerful than anthropogenic.

Thank You SSS

Regards

David

[Cycles]

SSS....Have a question, please help me to understand this.

I pasted Vostok values below. In comparing lines 3 and 4...When the Age of the ice is 7043 bp (line 3) and 9523 (line 4), and the corresponding "Mean Age of Air" is 3833 and 6220 (with CO2 ppm 254.6)....is the CO2 a mean value during the period from 3833BP to 6220BP (almost 2400 years).

Age of age of CO2

Depth the ice the air concentration

(m) (yr BP) (yr BP) (ppmv)

149.1 5679 2342 284.7

173.1 6828 3634 272.8

177.4 7043 3833 268.1

228.6 9523 6220 262.2250.3 10579 7327 254.6

266 11334 8113 259.6

302.6 13449 10123 261.6

321.2 14538 11013 263.7

331.6 15208 11326 244.8

full Vostok text at http://cdiac.ornl.gov/ftp/trends/co2/vostok.icecore.co2

[sunny starry skies]

SSS....Have a question, please help me to understand this.

I pasted Vostok values below. In comparing lines 3 and 4...When the Age of the ice is 7043 bp (line 3) and 9523 (line 4), and the corresponding "Mean Age of Air" is 3833 and 6220 (with CO2 ppm 254.6)....is the CO2 a mean value during the period from 3833BP to 6220BP (almost 2400 years).

Age of age of CO2

Depth the ice the air concentration

(m) (yr BP) (yr BP) (ppmv)

149.1 5679 2342 284.7

173.1 6828 3634 272.8

177.4 7043 3833 268.1

228.6 9523 6220 262.2250.3 10579 7327 254.6

266 11334 8113 259.6

302.6 13449 10123 261.6

321.2 14538 11013 263.7

331.6 15208 11326 244.8

full Vostok text at http://cdiac.ornl.go...tok.icecore.co2

I suspect you're fishing for trouble, and could easily understand it if you tried, but for the benefit of others who might be interested, and to demonstrate that there is no problem with ice core CO2...

Depth (m) = sample depth. These are not necessarily at every possible sample depth through the core, as it will depend on the research questions answered. For example in the Fischer et al paper we had the argument about, they took high-resolution samples around the glacial terminations they were intersted in, but lower resolution samples for other parts of the core. If you want to show the basic shape of the sequence throughout a core, you don't sample at every possible location due to the cost/time of sampling, unless it is specifically relevant to your research question. In this case, Vostok, which has a low accumulation rate, is not sampled heavily for the Holocene as other cores do a better job of giving Holocene CO2, additionally they were studying the whole core.

Age of the ice (yr BP) = the age of the ice that encases the sample. Literally, the age the molecules of water were deposited on the surface of the ice sheet. This is determined by a combination of annual layer counting and an age-depth model for the ice sheet. Ages can be verified by several means, including marker horizons and matching with isotope records and palaeomagnetism in ocean cores, which can be dated independently. [an aside... google 'ice core dating' and you find lots of creationists worried about the age of the ice cores.... facts really get in the way of a good conspiracy don't they ]

Mean age of the air (yr BP) = the age of the air trapped inside the bubbles. This is different from the age of the ice as, I'm sure you're aware, air can mix downwards a certain distance into the ice. Over a period of time, bubbles will be trapped in any one layer as the gaps leading towards the surface are gradually closed off. This is not instantaneous, but it is a calculable property, and is dependent on the deposition rate of snow on the surface and the temperature of the snow. For any one layer in the core, air bubbles inside it will close within a certain, identifiable time period - ~300 years for Vostok, ~140years for Taylor Dome, references in Fischer et al 1999. Neftel et al (with references) give Siple Dome's closure age as 22 years for its historic CO2 curve (the one that neatly dovetails with the Mauna Loa curve).

http://cdiac.ornl.go.../co2/siple.html

CO2 Concentration (ppmv) = what it says on the tin, with measurement errors quoted in the relevant papers. They are small, compared to the variations observed.

A really good review, which I would encourage you to read if you are interested is Raynaud et al, 1993: The Ice Core Record of Greenhouse Gases, in Science.

abstract:

http://www.scopus.co...Cn4UBDyFX1x%3a2

full article (not sure if it's free):

http://www.jstor.org...origin=elsevier

And please tell me you've not read Jawoworski's rubbish on the subject (some of your questions suggest you might) - some of his many flaws are highlighted here:

http://www.ferdinand...jaworowski.html

In all these cases, you'll find that the errors, other possible sources of error, solutions and issues are discussed in the relevant papers. All it takes is for you to read those papers with an open mind, and not one closed to the idea that actually, we do have a very good idea of the variations of CO2 over the past 800,000 (most recently Luthi et al 2008 in Nature). This crucially constrains the climate-carbon cycle connection back 800,000 years (natural CO2 range 170-300ppm), and places our alterations of it very firmly into context... here is a hockey stick that has nothing to do with Mann or Jones!

I think it is crucial to note that samples are not always taken at the maximum resolution, though in all the studies I've read, multiple samples were taken at each sampling depth, therefore constraining the errors. Any experimental scientist will tell you this, particularly if the analyses are expensive or time-consuming. The numerous Antarctic cores provide essentially the same data, with widely-varying sample resolutions, and with overlaps to directly measured values, so we can have great confidence in the CO2 record.

sss

Edited March 12, 2010 by sunny starry skies

[Cycles]

Thank you SSS for your post...I certainly will read the links you posted this weekend, much on my plate right now.

Again, thank you for your time and patience

Regards

David Dilley

[kold weather]

The short answer is anthropogenic aerosols, but I'll leave you to look up the IPCC AR4, to read and understand why temperatures don't always dutifully follow CO2 rise, as I've done enough research on your behalf. There'll be links on Skeptical Science too, which debunk most of the common denier arguments.

sss

Not quite the whole answer though, Joe B has been making this point for a while but the period between the 40s-80s was a prolonged cold phase in the N.Hemisphere, you had the PDO kick into a cold phase in the 40s (ironically the 40s was when NW Europe started to get more severe cold winters...) the AMO took longer to kick down and didn't really switch cold till the latter part of the 50s with any great vigour, but the 60s was when we had prime time cooling with both the AMO/PDO in thier respective negative phase, thus bringing down global temps. EVentually we came out of that phase in the late 70s and 80s into a double positive warming phase in the 90s...no surprise that is when the global warming also increased, esp between 88-98 when both the PDO/AMO flipped 'warm'.

For the UK it should come as no surprise that we saw the real up rise of the yearly CET's (+10s) between 1995-1997...which is not per fluke that the warmer phase of the Atlantic kicked in...

[Cycles]

Some of my prior posts on this thread asked the question about mean values of CO2 taken from ice core samples, thus dampening and hiding CO2 spikes.

Below is an intersting post by Ferdinand Engelbeen on the Yahoo Group "Climate Sceptics" forum.

This is an interesting post on another forum and it states...

"Looks like that the distribution of a one-time

atmospheric CO2 pulse in the ice core bubbles is

smoothed assymetric, with a long tail over time.

Thus, indeed any fast change in constituents of

the atmosphere would be smoothed in the ice core.

For the large long-term changes

(glacials-interglacials), that doesn't play much

role, but any relative fast change (e.g. ocean

influences like the PDO) would be missed. Despite

that, other medium timespan changes like D.-O.

events (taking two to five thousand years) are

seen in the temperature proxy (ice isotopes) as

well as in the CO2 (gas level) data records. With

CO2 lagging temperature with some 1200 +/- 700

years (see

<http://www.ncdc.noaa.gov/paleo/taylor/indermuehle00grl.pdf>http://www.ncdc.noaa.gov/paleo/taylor/indermuehle00grl.pdf

).

Regards,

Ferdinand Engelbeen

[VillagePlank]

...

"Looks like that the distribution of a one-time

atmospheric CO2 pulse in the ice core bubbles is

smoothed assymetric, with a long tail over time.

...

That's really curious.

Such that is so curious I've looked and have no idea what it actually means. Assymetric rounding is such that there is rounding around the 0.5 since 0.5 gets rounded up under such a scheme so that there is a bias towards rounding upwards.

What the hell (a) smoothed assymetric, I must admit, is completely beyond me.

Edited March 13, 2010 by VillagePlank