This comment from Dr. Robert Brown at Duke University is elevated from a comment to a full post for further discussion. Since we have a new paper (Shepherd et al) that is being touted in the media as “certain” using noisy data with no stable baseline, this discussion seems relevant.
So wait, you are saying that fossil fuels do not cause warming, but that if we shift away from them to clean energies, there is a risk of the earth cooling? Uh, could you just think that through and try agan?
No, that’s just some people on the list who are “certain” — with no more grounds than those of the warmists — that the Earth is about to cool. In the long run, of course, they are correct — the current interglacial (the Holocene) is bound to end at some point soon in geological time, but that could be anytime from “starting right now” to “in a thousand years” or even longer. Some are silly enough to fit a sine function to some fragment of data and believe that that has predictive value.
The problem is that nobody knows why the Eocene ended and the Pleistocene (the current ice age) started, and nobody knows exactly where and why the Pliestocene is a modulated series of glaciations followed by brief stretches of interglacial.
There are theories — see e.g. the Milankovitch cycle — but they have no quantitative predictive value and the actual causal mechanism is far from clear. So we do not know what the temperature outside “should” be, with and/or without CO_2. We do know historically that the Little Ice Age that ended around 200 years ago was tied for the coldest century long stretch of the entire Holocene — that is, the coldest for the last 11,000 or so years (where it might surprise you to learn that the Holocene Optimum was between 1.5 and 2 C warmer than it is today, without CO_2).
So the fact of the matter is that there is a risk of the Earth cooling — in fact, there is a risk of a return to open glaciation, the start of the next 90,000 year glacial era — but it is not a particularly high risk and we have no way to meaningfully do much better than to say “sometime in the next few centuries”. CO_2 might, actually, help prevent the next glacial era (or at least, might delay it) but even that is not clear — the Ordovician-Silurian ice age began with CO_2 levels of 7000 ppm. That is around 17 times the current level, almost 1% of the atmosphere CO_2 — and persisted for millions of years with CO_2 levels consistently in the ballpark of 4000 ppm. If the Earth’s climate system (which we do not understand, in my opinion, well enough to predict even a single decade out let alone a century) decides it is time for glaciation, I suspect that nothing we can do will have any meaningful effect on the process, just as I don’t think that we have had any profound warming influence on the Earth so far.
The fundamental issue is this. We have some thirty three years of halfway decent climate data — perhaps twice that if you are very generous — which is the blink of an eye in the chaotic climate system that is the Earth. There has been roughly 0.3 C warming over that thirty-three year stretch, or roughly 0.1 C/decade. It is almost certain that some fraction of that warming was completely natural, not due to human causes and we do not know that fraction — a reasonable guess would be to extrapolate the warming rate from the entire post LIA era, which is already close to 0.1 C/decade. It is probably reasonable to assign roughly 0.3 C total warming to Anthropogenic CO_2 — that is everything, not just the last thirty years but from the beginning of time. It might be as much as 0.5C, it might be as little as 0.1C (or even be negative), but the physics suggests a warming on the order of 1.2 C upon a complete doubling of CO_2 if we don’t pretend to more knowledge than we have concerning the nature and signs of the feedbacks.
At the moment there is little reason to think that we are headed towards catastrophe. When the combined membership of the AMA and AGU were surveyed — this is surveying climate scientists in general, not the public or the particular climate scientists that are most vocal on the issue — 15% were not convinced of anthropogenic global warming at all, and over half of them doubted that the warming anthropogenic or not would be catastrophic. It’s the George Mason survey — feel free to look it up. The general consensus was, and remains, that there has definitely and unsurprisingly been warming post LIA, that humans have caused some part of this (how much open to considerable debate as the science is not settled or particularly clear), that there is some chance of it being “catastrophic” warming in the future, a much larger chance that it will not be, and some chance that it will not warm further at all or even cool.
The rational thing to do is to continue to pursue the science, especially the accumulation of a few more decades of halfway decent data, until that science becomes a bit clearer, without betting our prosperity and the prosperity of our children and the calamitous and catastrophic perpetuation of global poverty and untold misery in the present on the relatively small chance of the warming being catastrophic and there being something we can do about it to prevent it from becoming so.
So far, if catastrophe is in the cards, the measures proposed won’t prevent it even according to those that predict it! In fact, it won’t have any effect on the catastrophe at all according to the worst case doom and gloomers. We could stop burning carbon worldwide tomorrow and if the carbon cycle model currently in favor with the CAGW crowd is correct (which I doubt) it would take centuries for the Earth’s CO_2 level to go back to “normal” — whatever that means, given that it varies by almost a factor of 2 completely naturally from glacial era to interglacial. In fact, according to that model the CO_2 levels will continue to go up as long as we contribute any CO_2 at all, because they’ve stuck an absurdly long relaxation time into their basic system of equations (one with very little empirical foundation, again IMO).
Again, I suggest that you reread the top article carefully. I actually do not think it is the best example of Monckton’s writing — a few people have noted that its tone is not terribly elevating, and I have to agree — but I sense and sympathize with his frustration, given the content of the article. There is a stench of hypocrisy that stretches from Al Gore’s globe-hopping by jet and his huge house and large car all the way to a collection of people with nothing better to do who have jetted to Doha to have a big party and figure out how to continue their quest for World Domination, hypocrisy with king-sized blinders that seem quite incapable of permitting the slightest bit of doubt to enter, even when bold predictions like those openly made in the 2008 report come back to bite them in the ass.
I myself am not a believer in CAGW. Nor am I a disbeliever. The only thing that I “believe” in regarding the subject is our own ignorance, combined with a fairly firm belief that there is little reason to panic visible in the climate record, and that is before various thumbs were laid firmly on the scales. Remove those thumbs and there is even less reason to panic.
My own prediction for the climate is this. We will probably continue to experience mild warming for another ten to twenty years — warming on the order of 0.1C per decade. It will probably occur in bursts — the climate record shows clear signs of punctuated equilibrium, a Hurst-Kolmogorov process — most likely associated with strong El Ninos (if we get back to where strong El Ninos occur — the last couple have fizzled out altogether, hence the lack of warming). In the meantime, we will without much additional effort beyond existing research and the obvious profit incentives drop the cost of solar power by a factor of four, and it will become at least competitive with the cheapest ways of generating electrical power. We will also have at least one major breakthrough in energy storage technology. The two together will cause solar to become more profitable than coal independent of subsidy, for much but not all of the world. Without anybody being inconvenienced or “doing” anything beyond pursuing the most profitable course, global consumption of carbon will then drop like a rock no matter what we do in the meantime.
Beyond twenty years I don’t think anybody has a clue as to what the temperature will do. I don’t even have a lot of confidence in my own prediction. It wouldn’t surprise me if it got cooler, especially if the Sun enters a true Maunder-style minimum. Nor would it surprise me if it got warmer than my modest prediction. But either way, I think roughly 500 ppm is likely to be the peak level of CO_2 before it comes down, and it may well fail to make it to 500 ppm, and even the catastrophists would have a hard time making a catastrophe out of that given 0.3 C of warming in association with the bump from 300 to 400.
We could make it more likely to cut off before 500 ppm — invest massively in nuclear power. Nuclear power is actually relatively cheap, so this is a cost-benefit win, if we regulate them carefully for safety and avoid nuclear proliferation (both risks, but less catastrophic than the inflated predictions of the catastrophists). But I don’t think we will, and in the end I don’t think it will matter.