I would be interested in your thoughts about this. I began to have a feeling of outrage again on a number of grounds:
Where have you got to about all this?
My personal take? That you have a point. Climate is innately variable, and most of the variations that we have seen have been driven by orbital issues or by the sunspot cycle. That is simple fact that nobody disputes. The Gore charts which were (and are) used to show the relationship between CO2 and ice ages is mendacious, as everyone knows that the Milankovitch cycles - orbital issues of the Earth around the sun - drive these cycles. Researchers have tried to sort out the chicken and egg - CO2 variations ahead of or behind climate changes - and have been unable to draw a satisfactory conclusion. Which is to say they all plump for "before" but their data do not, in truth, support this.
Carbon dioxide as dominant driver?
The single greatest long-run support for CO2 as a dominant signal is the long run cooling that followed the rise of the Himalayas. These weathered, and their weathering chemistry (still) removes CO2 from the atmosphere. That, without doubt, cooled the climate and triggered the long series of glaciations that are themselves triggered by orbital behaviour.
The problem is, however, that the concentrations at which changes in CO2 have gross effects as a greenhouse gas are probably well below current levels. The Himalayas may have cranked CO2 down below 100 ppm. When it is where it is now - four times that level - the atmosphere is black at the relevant wavelengths, and adding more is going to have relatively marginal effects. Gases such as methane and nitrogen oxides, particles such as soot and sulphates from combustion, or dust from farming are much more likely to be important additions in the current state. Indeed, we know very well that Arctic melting is down chiefly to particulates darkening the ice, and to a current that has switched to pushing warm water into the Arctic ocean. I'll get back to that in a moment.
This last brings up the issue of propaganda and mendacity. An unpleasant side of this debate is the coarse aggression of the "converted" against the pretty much anyone who is not of their number. I recall working alongside IPCC authors in the 1990s, where the atmosphere then was fraught and is now, of course, even more polarised. Even in the 1990s, there was a strong sense that a vast lobby of malign interests were set to destroy the efforts of the true band of brothers. You were with them or against them. Science granting authorities would only fund schemes with supportive assumptions built into them, and major journals were even then in crusader mode. (Now, both AAAS Science and Nature rail at "denialists" with every issue. It is notable that the last IPCC document took it as read that there was significant climate change, and that what was marginally debatable was whether this was caused by humans.)
Let me given on example of the consequences of the 'true believer' approach. As you are aware, temperature values have been steady for quite some time. This is being attributed to "heat lost to the oceans." The relevant paper is Yu Kosaka and Shang-Ping Xie (Nature 501 pp403-407 (2013) doi:10.1038/nature12534). This consists entirely of a modelling exercise. There are no data involved, yet it is the peg on which the rescue of the warming trend is hung. It is speculation, expressed through a complex computer model. Indeed, it is now the habit of prestigious journals to publish papers that are based on modelling of data obtained from other models. All of the temperature series that are used are necessarily adjusted (choose your word carefully!) to reflect the changing circumstances to the sites from which historical measures have been taken: eg Heathrow was a grass runway in the 1930s and is now a concrete arena, five or so degrees hotter by virtue of its new physical geography.
Other factors in play
Carbon dioxide is now something like 48% higher than it was in pre-industrial times. If it was an important driver of climate at such concentrations, one would expect to find a major signal. But we have to scrabble around in the data to find anything: half a degree, after much massaging. Meanwhile, the models take scant account of the other factors that humans have generated, such as - in particular - soot. Regionally, soot has an immense impact, India cuts its incoming light by large percentage in the burning season, and that heats the air. We pump out large amounts of sulphate - which is generally reflective, and which nucleates clouds, which are very reflective indeed - and we fix enormous amounts of nitrogen oxides. These are greenhouse gases, but they are also fertilisers that darken the Earth due to more plants, including desert varnish, a lichen-and-bacteria complex that darkens the soil of desert regions. My point is that there are a lot of other factors at work, yet CO2 is always put at stage centre.
Saturated CO2 spectra and models
Consider the implications if the current atmosphere is already largely black at current CO2 concentrations. First, additions would have limited climatic effects, even if there are other long run undesirable consequences, such as ocean acidification. Second, it would seriously bias our interpretation of the past. The long run cooling trend to which I alluded earlier, consequential on the rise of the Himalayas. is the result of concentration at which the atmosphere is not black, and where adding or removing CO2 has a major effect. However, that would have no relevance to the present, where the atmosphere is black.
It is strange, therefore, that climate models have no allowance built into them for this saturation effect. The assumption is that something called the Beer Lambert law applies, whereby absorbance is linearly related to concentration. That only works when the absorbing agent is very dilute as compared to its saturation levels. By analogy, ink added to water first tints it, and the resulting tint is a good indication of the amount of ink that is involved. Measure how much light you find absorbed, and you can estimate the concentration of the ink. However, adding ink to water that is already ink-black water will give you so tiny an increase in absorption as to make measurement very difficult. The marginal increase in absorption is very small at high concentrations, and the curve that relates concentration to percent of the light absorbed is an asymptote. Our current atmosphere is right on the flat bit of the asymptote, which is not at all taken into account in the models that are used.
Is there climate change?
So, bottom line: is there climate change? Of course, because the climate bounces around all the time. We are recovering from an ice age that had the North sea and Scotland under a kilometre of ice. Glaciers covered much of North America. Finland is still rebounding from its glacial burden, rising a centimetre a year. The Sahara was a prairie, the Mediterranean an salt flat and the Black sea a fresh water lake, around which settled farming began. Indeed, there is speculation that the filling of the Black sea was the origins of the Noah's flood legends. But that was entirely due to natural variation - orbital issues, the fact that ocean currents wander about like a hose pipe in a swimming pool.
But is there anthropogenic climate change? Equally, of course there is. We have ploughed up much of the land that can be farmed and irrigated a great deal that once could not. We have pumped fertilisers into the ocean, rendering it different in many separate ways. We have dumped soot and dust onto any surface that will take it. Human construction is roughly the volume of the entire Himalayas. We have changed atmospheric chemistry and physics with gases, particles, probably water vapour. But is the chief cause of whatever humans are doing down to carbon dioxide? Personally, I doubt it. Soot alone accounts for the entire signal that we measure - actually, rather more than accounts for it. Carbon dioxide may be important in the higher atmosphere, where particulates do not much enter, but this is also the domain of water vapour, and that has gone up a lot even in the scant period in which we have been able to measure it.
But is it down to CO2?
The shameful thing is that the counter-views have been crushed in the academic community. Simple, factual questions, such as how dark is the atmosphere at CO2 wavelengths, do not get asked. It took the Star Wars program to show that a CO2 laser could not be used as a weapon, because the atmosphere absorbed its output very quickly. Early attempts to use CO2 lasers as free air data transmission conduits, replacing microwaves dishes, also ran into the same problem. It's already black, very very black, that atmosphere.
The bottomest of the bottom lines is that this band waggon has now rolled so far that whatever the truth of the matter, its inertia will demand that commerce behave as though the story is valid, whether it is or it is not. The matter is not now open to public discussion in state circles - whatever individual legislators may tell you in private - and public questioning of these issues is taken as a sign of questionable judgment and general wickedness. It may be pusillanimous to say this, but it is best to take the grants and shut up.