Even more impressive is the fact that, though astronomic or cosmic cycles and positions can be predicted with utmost precision, weather and climate on Earth still and most obviously can not. It seems there are many other factors involved; like - well, perhaps, indeed, the makeup of a planet's atmosphere.
So, the following is premised on the assumption that, just as does the Sun's intensity, the position of Earth in Space, and even its own geothermal heat, atmospheric carbon dioxide can and does influence this planet's surface temperature; at least it is doing so under the current circumstances.
If it doesn't, then other explanations have to be found for the phenomena observed.
If it does, the question is how, and how much; the increase in temperature induced by atmospheric CO2, as given by different authors, lies somewhere in the range of +0 °C to +30 °C, which almost renders any discussion useless.
The following, in parts 1 & 2, is therefore hypothetical in its attempt. It presents one possible way of interpreting the depictions of the data as found in public.
CO2: Photosynthesis and Climate Change
The following shall be discussed here:
- There has been a natural climate fluctuation for at least a million years
- This could, at least in part, be biological by cause
- Humans have most possibly played a role in the latest stages
There has been much discussion about climate change, and most of it refers in some way or another to the Vostok ice cores and similar evaluations.
Under the premise that the data gleaned from these is correct, their interpretation is correct (which is by no means certain, as the recent controversy of Mann vs. Ball shows), and their publicly available depiction in the graphs referred to below as well as other public statements are correct (which is by no means certain either), it would seem to follow that for the last million years, at least, the Earth's climate (rather: it's mean average surface temperature) has not only constantly changed, but that this change was a) confined in range and b) quite regular in nature.
During this time, the publicly acknowledged culprit behind climate change, the amount of carbon dioxide in the atmosphere of this planet, in equally confined and regular fluctuations, did not register above 290 ppm, its peak value before industrialization, nor did it fall below 180 ppm; not in the 800,000 years evaluated in total, and not in the 400,000 years - perhaps only 200,000 years - of supposed human existence contained therein. This differs wildly from the time before; and so other factors come into play as well, which will be touched upon below.
Such a fluctuation range of 110 ppm (or 0.011%) in natural polar atmospheric CO2 levels could intuitively be considered as negligible; however, the corresponding polar atmospheric temperature fluctuation range of around 12 °C, seems quite enough mark the difference between an "ice age" or glacial and a "warm period" or interglacial - which, by the way of speech, declares glacial epochs to be the norm.
This is borne out by the Vostok ice core data as referenced below: during the last 0.8 million years, the top half of the 12 °C range contains less than half the data; and it corresponds to a current global mean temperature of around 15 °C, which is not very much above the freezing point of water - even though the evaluation of the Vostok ice cores show us to be, right now, at or near the end of the current interglacial period and therefore at or around peak temperature.
More precisely, in comparison with previous interglacial peaks, previous peak CO2 levels were almost reached, before the massive utilization of fossil fuels began to artificially enhance them some 200 years ago, but the natural peak temperatures were not; nor do they show a tendency to that effect.
In fact, for some 10,000 years now, the polar atmospheric temperatures seem to have entered a "stable climate" anomaly, fluctuating tightly around a new stable mean. This coincides with the arrival of modern man.
Interpreting publicly available depictions of scientific data is always difficult and tends to be inaccurate; however, it is these that are driving the discussion, so it might help to take a step back for a closer look at what they actually show.
500 million years of climate change
The graphs presented here have been chosen from a variety of similar depictions, which seem to have been agreed upon as valid.
They cover three time frames, 0.4 and 0.8 million, 5 million and 600 million years, and later focus on the last 10,000 years. As one can imagine, the smaller time frames have a reasonable margin of error, the larger ones a significant one.
There may be more links to other graphs and external pages throughout this text to illustrate a given point, but they basically do not differ from the ones referenced here.
· The Vostok ice core data, 400,000 year overview:
· The Vostok ice core data, 800,000 year overview:
· The 5 million year overview (Wikipedia):
· The 65 million year overview (Wikipedia):
· The 500 million year overview:
Choosing the parameters
As part of the planetary and terrestrial fauna, we as humans are completely insensitive to atmospheric CO2 levels currently negligible to our wellbeing, which are, at the moment, being kept far below even the normal level in our own lungs by the constant efforts of floral photosynthesis - to which these levels, especially if terrestrial, are crucial; so while the terrestrial fauna is insensitive to atmospheric CO2 levels as low as today, the flora is not.
This differential sensitivity is reversed once atmospheric CO2 levels reach 2000 ppm and above, or about ten times the current level; at which point it begins to displace the atmospheric oxygen vital to terrestrial fauna; these levels were reached in the past (it should be stressed that, though terrestrial and marine environments and life ultimately share the same carbon and oxygen pool, the waters hold their own specific reservoirs).
However, the surrounding temperature, which by the way does not reach levels ten times the current value, even under much higher atmospheric carbon dioxide levels, directly affects our comfort, as we can feel it; and more importantly, water-borne, protein-based life on Earth has a viability window of only about 0-100 °C (higher life forms even less than half that range, topping at around 42 °C).
So, despite these scenarios not having come into effect yet, with or without human interference, worries are that this planet could develop a positive feed back loop or "runaway" icebox, or a similar greenhouse effect, which would drive its surface temperature irretrievably out of the viability window in one or the other direction; especially in the direction of heat, as it is possible to heat, but impossible to overall cool the environment in order to counteract.
Within that viability range, especially terrestrial plants both need and survive higher CO2 levels and higher temperatures (up to 55 °C, with their general optimum at around 42 °C) to thrive than terrestrial animals in general - which in turn must feed upon them, as animal life is dependent on plant life - and current peak values in particular; so one could say that, even at this time, the system in general is slightly tilted in disfavor of the flora and in favor of the fauna - which includes humans.
This may be significant. The common range, in which both terrestrial plants and higher animals can comfortably survive long term, stretches from about 0 °C (lower limit for flora) up to 42 °C (upper limit for fauna) for environmental temperature and from about 2000 ppm (upper limit for fauna) down to - surprise! 180 ppm (lower limit for flora) for atmospheric CO2 levels. That could be significant as well.
A look at the last 800,000 years
For the past 0.8 million years, but not for much beyond that time frame, the Vostok ice core graphs of 400,000 and 800,000 years
show a tight relationship between polar air temperatures, polar atmospheric carbon dioxide levels, and not to be overlooked, the passage of time; but cause and effect are in dispute, and inertia in both directions has to be considered.
Positive and negative feedback between the carbon dioxide level of an atmosphere and its temperature with different agents forms a high probability as well. And just to mention it, CH4 (methane) levels are equally closely correlated to polar temperatures, some say even more.
Theoretically, one or more of all three factors - polar temperatures, polar atmospheric carbon, and time could be a cause; and each (except time) could also be an effect.
Taking CO2 as a widely used representative for atmospheric carbon, the natural and periodic fluctuation over the last 800,000 years of polar atmospheric temperature and carbon dioxide levels could imply that neither CO2 levels nor temperature are the driver, but that time is, with the solar/planetary system running through a combination of complex periodic astronomic constellations - in which case there would be very little, if nothing, that could be done about it, since any change in human behavior would be without effect be on the extraterrestrial cause for natural climate change.
The wider scope: 5 - 500 million years
However, looking at the 5 million year resolution, these fluctuations and their results are not as regular or constant as one might expect under such a premise, assuming all cosmic cycles are known; after having fallen by about 6 °C during that time frame, this planet's overall average mean temperature and corresponding CO2 levels seem to have remained relatively consistent for the last 0.8 million years; while their short-term fluctuations, becoming more pronounced and regular over time, about 1.2 million years ago quite suddenly changed their frequency from 41,000 to 100,000 year cycles; at which point not only does the former bottom line now form its upper limit, but a new bottom line is also slowly established, between which two the span of polar atmospheric CO2 levels and temperatures have been augmented and limited to a stable maximum of 100 ppm and 10 degrees respectively - strangely enough for almost exactly the 0.8 million year time frame of the Vostok ice cores. Was Antarctica ice free up to then?
When did it all begin? The steady and constant fluctuation of atmospheric temperature over millennia seems to have begun some 35 million years ago, the underlying trend to lower temperatures some 15 million and the final trend to increase the spread or amplitude of that fluctuation some 7 million.
While the atmospheric carbon correlation is unknown, some of these numbers will turn up again later in a another context; but in the 500 million year time frame all bets are off.
By far most of that time, the average global temperature seems to in no way whatsoever correspond with the atmospheric carbon dioxide levels; moreover, it regularly seems to level off at around 25 °C, no matter how high that concentration becomes.
Whatever mechanism is driving the recent and ever-increasing natural climate change cycles over the last few million years, that mechanism itself seems to react to (or cause) a change in mean temperature: the more that falls, the more extreme and regular the changes in atmospheric CO2 levels and temperatures become; and so the mechanism in question could be reacting to it's own lowering of the median atmospheric temperature (and with that, CO2 levels) in an overall cooling positive feedback loop.
This development, the fluctuation itself of atmospheric temperatures and carbon dioxide levels between two thresholds, with a steadily widening spread in amplitude and, coincidentally, wavelength, and a coincidentally dropping median, until reaching the present, if most likely temporary final stability, could point more to internally triggered feedback loops, rather than independent, external forces.
Evaluating the ice core data curves
The publicly available graphs of the Vostok ice core data show that, for the past 800,000 years, there has been a sequence of climate changes on this planet from ice ages to warm periods, each natural cycle lasting very roughly around 100,000 years. In detail, we find that
· polar atmospheric CO2 levels and temperatures coincide, fluctuating naturally and periodically between around 180 and 290 ppm absolutely and +3 and -9 °C in relation to today;
· these fluctuations are regular, but not of equal length; a short and sharp warming period is followed by a protracted cooling period:
· a sharp rise in both polar temperatures and atmospheric carbon dioxide levels within a time period of around 10,000 years,
· to the level of 290 ppm and +3 °C relative to today; at which point they do not rise any further, nor level out, but abruptly flip to a slow decline during the following 90,000 years into the next glacial period;
· upon reaching the lower level of 180 ppm and -9 °C relative to today, they do not drop any further, nor level out, but abruptly flip to the next sharp rise that again lasts about 10,000 years, with both CO2 levels and temperatures rising almost ten times faster than they previously dropped;
· this behavior becomes more marked over time, corresponding with tighter data.
To note, the fluctuations within both atmospheric carbon dioxide and temperature levels of the last 0.8 million years are shown to be far greater than the variation in their minimum and maximum values; giving rise to the thought that, though the planetary conditions may run rampant within their natural boundaries, they can not pass certain upper or lower limits under a given situation - and that the correspondence of these with possible other boundaries might not be purely coincidental. There are no...
To take an even closer look at the details, the available Vostok ice core data curves for polar atmospheric temperatures and CO2 levels, which thankfully both correspond in time (if not always in amplitude), were marked with their "peaks" and "troughs" and evaluated, while endeavoring to keep the unavoidable outcome manipulation in pinpointing these to a minimum.
The 800,000 year amplitudes
Over the past few million years, the amplitude of natural climate change shows a trend to steadily increase; and though the published graphs for the past 0.8 million are not quite consistent in these values, the average polar atmospheric temperatures and CO2 levels that could be extracted from them are:
Interglacial temperature peaks in °C, relative to today:
-1, -2, -1, -2, +2, +3, +2, +3, +0
Relative temperature peak range: -2 °C | + 3 °C |, or 5 °C of 12 °C in total
Interglacial CO2 level peaks in ppm, absolute:
260, 240, 260, 250, 280, 300, 275, 280, 290 [pre-industrial]
Absolute CO2 peak range: 300 ppm | 240 ppm, or 60 ppm of 110 ppm in total
Glacial temperature troughs in °C, relative to today:
-8, -8, -8, -7, -8, -8, -8, -9, -9
Relative temperature trough range: -7 °C | -9 °C or 2 °C of 12° in total
Glacial CO2 level troughs in ppm, absolute:
190, 175, 170, 190, 190, 180, 180, 180, 180
Absolute CO2 trough range: 190 ppm|170 ppm or 20 ppm of 110 ppm in total
If this is the case, then the lower limit for both temperature and CO2 levels (1/6 of total range) is defined more sharply than the upper limit (1/2 of total range), suggesting that if there are terrestrial feedback loops driving the natural regular climate change cycles, the low point trigger would be more sharply defined than the high point trigger; and, while the spread between these points increases over time, the correspondingly sudden flip-flop in both values does suggest such triggers.
The 800,000 year wavelengths
Over the past few million years, but more markedly the last 0.8, the wavelengths of the natural climate change cycles also show a steady trend towards a slow increase.
Beginning 800,000 years ago (and allowing for some interpretation), the time elapsed (in thousand years) is,
- from interglacial peak to interglacial peak:
[offset: 10] 95, 105 (anomalous double peak), 100, 80, 75, 90, 115, 130, [offset: 0]
- and from glacial trough to glacial trough:
[offset: 0] 60, 70, 140 (anomalous double peak), 90, 85, 100, 115, 120, [offset: 20]
- the duration of interglacial peaks (in thousand years) is:
10, 45, 80 (anomalous double peak), 40, 35, 25, 15, 10, 20
- the duration of glacial troughs (in thousand years) is:
0, 50, 25, 60, 50, 50, 75, 100, 110
(Note the last glacial trough is offset to today by 20 thousand years, not 10.)
Combined, the waves of interglacial peaks and glacial troughs have steadily increased both in length and height over the last 0.8 million years with 9 natural climate change cycles; over time, the glacial troughs have grown longer, with somewhat lower temperatures, while the interglacial peaks have become shorter, but hotter.
The glacial bottom line remains relatively constant in both atmospheric CO2 levels and temperature, dropping very slightly, if at all, while both rise as a trend during interglacial peaks; excepting the very recent temperatures, which, compared to recent CO2 levels, are lagging behind.
It would be difficult to discern from this alone, which one of the two values, atmospheric CO2 levels or temperature, would be the primary driving force behind this kind of tripwire behavior, i. e. which would be the one more likely to act as or react to a trip value, triggering a counteraction; either with different CO2 levels acting as a variable in atmospheric insulation, or variable temperatures raising or lowering the storage or sequestration of carbon in the environment.
The arctic nature of the ice core measurements holds another difficulty: though variable in season, atmospheric carbon dioxide levels will be more or less the same both in the polar and equatorial regions of a planet; but temperatures most certainly are not.
And to assume that equatorial or even mean temperature fluctuations, due to any given cause, will equal the fluctuations in polar temperature, is daring as well, and seems to be refuted for at least the last 250 million years, in which polar temperatures are said to have fallen much further than equatorial ones (to wit: the projected anthropogenic global climate change is calculated very roughly at 1 °C increase for every 100 ppm increase in atmospheric CO2 levels; the antarctic Vostok ice cores, equally roughly, show a 10 °C difference for every 100 ppm).
But even if the relative difference in polar temperatures of -9 °C | +3 °C to today were reflected 1 : 1 in equatorial values, the mean of which currently lies at about 29 °C, a global drop in temperature of 9 °C would still leave it at a comfortable average of 20 °C, with no detriment to plant or animal life; and a rise of 3 °C would make it only slightly hotter on average than today, but still not dangerously so, especially not to plants - which, by the way, holds true the other way round: a slight change in equatorial temperatures could be reflected in a large one in the polar regions of this planet.
Comparing the data
A qualitative comparison of this data in two graphs shows that both peak & trough wavelengths, with the exception of the anomaly 600,000 years ago, as well as the duration of the glacial periods have steadily lengthened; while that of the interglacials - our current period - has shortened.
But, while both maximum and minimum polar temperature and atmospheric CO2 levels correlate quiet well generally over the observed stretch of time (though not necessarily before), this last and current period (of 20,000, not 10,000 years) breaks the trend in both duration of the glacial and interglacial, as well as the maximum temperature; and especially that last deviation does not seem to be an artifact.
[Continued in The Vostok Ice Cores pt. 2: Speculation, Suggestion and Mystery]