G'day Blacknad,
A really reasoned argument. Thank you.
What you say may well be true. It is a primary difficulty in climate change that so little records exist and the study of historic climate has for a very long time been consigned to a very low level. It is also more difficult to study historic climate than simple look for fossils to study evolutionary paths. I understand how difficult it is to extrapolate from the scant fossil record for many periods just what was around let alone attempting to understand climate on a world scale. The evidence is not directly available and even indirect evidence is difficult to locate and subject to interpretation.
In broad brush terms the climate of the world is somewhat known. The concentrations of CO2 has at least a degree of certainty to it as does the concentration of oxygen, etc. So arguments about what happened in the past can only be as good as the evidence thus far uncovered.
How about a simple counter logic to yours as a starting point. This interglacial period has been of much longer duration than the "average" for this ice age. The oscillation of interglacial periods to glacial periods seemed to have settled down to a fairly consistent pattern starting around 120,000 years ago. This interglacial period breaks the mold in that it is several thousand years longer than the norm.
If peat bogs that are under permafrost existed in equal quantities during all interglacial periods then it would be expected that the extra years would eventually cause a difference in pattern of release to occur. The same goes for the retreat of glaciers and a number of other things. Given a long enough interglacial period and glaciers melt, the permafrost retreats etc.
Since humans have certainly not extended this interglacial period by several thousand years then the differences could also be considered to be natural, could they not?
I also have some problems with the suggestion that the numbers of ruminant animals being fewer in previous interglacial periods. We were not around to count them as we now are. We can currently say with some accuracy how many cows exist on this earth but we have no idea what that figure was even 2,000 years ago. However it is reasonable to assume that there were large numbers of ruminant animals (and they are not the only methane producing animals by the way) in the past. There is evidence of vast herds that roamed the earth in past geological times and in much more recent times. Before man?s impact in large numbers in many parts of the world, the numbers of herbivores that produce methane are actually so large they are difficult to imagine. I do remember vaguely a passage from an explorer?s diary of a couple of centuries back where he was talking of the migration of grass eaters in Africa, saying that he witnessed the movement of many millions of animals that stretched from horizon to horizon and took literally days to pass. While that is anecdotal and it could be argued that was a concentration in one small area and does not necessary mean than the whole world was overrun by herbivores, I still find it useful as a way of at least considering that number of ruminants in the world is not necessarily determined by whether man decided to domestic some of them.
Think of buffaloes as another example. The numbers of these creatures during the last interglacial periods would be truly breathtaking. Indeed, until man decided to slaughter them a few hundred years ago, it is quite possible - at least from the information I have read - that they existed in far greater numbers than the grazing stock that eventually replaced them.
This is one of the real problems in discussing climate change. To argue effectively your expertise needs to be truly immense, covering a large number of dissimilar fields. I lay no such claim and so I'm open to any discussion as to the number of animals that existed over time or evidence that what I have just suggested is wrong. I'm dredging into memories of study that is not directly related to my interests to address what has been suggested, and obviously I could be mistaken.
It is also true that methane went from nothing 30 years ago to the big bogie today. But this seems to have happened without any correlating increase in evidence as to why this has occurred. Have studies uncovered prior correlations between methane and climate from ice cores for instance other than the obvious that there should be somewhat more methane in warmer periods?
It is true in one ice core study that methane concentrations have changed from a stable 600 ppb (and parts per billion is what we are talking about here) to around 1400 ppb today (actually there are higher figures but these are not from ice samples but from air samples), with the trend of acceleration starting around 1800. While the acceleration has been in modern times, it is the 1800 start that would give me pause for thought if I was trying to establish a correlation between methane concentrations and human activities.
In earlier ice cores there has been shown a small correlation between fluctuations in methane and climate. But that should be expected. The warmer the climate, the more methane that should be produced. What the correlations do not show is methane CAUSING any climate change. As best as can be analysed, the methane fluctuations follows the climate (a slight lag has been picked up in some studies) and then we get right back to a chicken and egg question. But in this case the likelihood is much less than methane came first since there is such an obvious explanation for fluctuations simply due to increased biological activity, photosynthesis etc during warmer periods.
Finally, if methane really is a greenhouse gas 30 times or 50 times as effective at trapping atmospheric heat than CO2 for instance, so what? Its concentrations could be in the order of several magnitudes higher and it would still be dwarfed the effect CO2 is said to have and the effect that water vapour really does have.
I do hope this gives some pause for thought even if you do not agree with a word written. I find the very best ways of assisting me in research is to have someone with a violently counter view review it. Those that agree with you rarely suggest anything that actually makes you think about your own position or, if necessary, alter it.
Richard
