Over at Climate Audit (Steve McIntyre’s site) I’m sorry to say I’m partly responsible for starting a big discussion on climate sensitivity. I’m Andrew by the way.
Please don’t add to it though, I’m trying to move the discussion to
Anyway, I seem to have made some people angry, what with them insisting I’m wrong in various ways, and taking some comments personally. I think I’ve apologize for my most egregious offenses, and mistakes. I would like to thank Pat Keating for explaining why my assumptions about positive feedback were just a bit naive. But, Arthur Smith seems to think that it’s pretty clear that we know the feedbacks add to together to be positive. Why? Because the smart people say so! More seriously, he seems to not get that at no point has anyone seriously considered the possibility (that they are negative), and it is in fact fair to assume so. Nevertheless, he has pointed out that positive feedback is allowed. This is true, as long as positive feedback is small enough, say, amounting to at most a degree. Given their insistence on values of a raw climate sensitivity of 1.5 (of which I am suspicious) that means that it is reasonable to assume at most a climate sensitivity of 2.5, if the system is to remain stable. Nevertheless, Arthur actually believes that the range is something like 2.5-4, meaning the upper bound I just derived from his musings is his lower bound! The critics of Lubos, incidentally, aren’t actually being fair. I asked Lubos, and their “properly calculated value” of 1.35 is well within his error margin. Well, anyway, the real reason he’s wrong is actually that the feedbacks don’t add up to a big positive number, since he ignores negatives. Also, the statement that ice age data were used to obtain climate sensitivity is patently absurd. Why? Because using that data, I would obtain a climate sensitivity of more than 12! So in a way, he’s right, the ice data would mean feedback is higher than we think. But he completely misunderstands the data, evidently because Algore taught him about Ice Ages. Well, in my earlier post, I explained that CO2 is not the driver in these situations, but a teeny weeny amplifier of the initial forcing, which is orbital. Anyway, the issue over how strong climate sensitivity can only be sorted out once you know all the forcings well. The “Level of Scientific Understanding” on most forcings is classified by the IPCC as low. What does this mean? Well, in order to know what can, in reality, be attributed to CO2, you must be able to subtract all other effects, including the very poorly understood aerosols. Not to mention the fact that the IPCC and others assume (bad assumption) that the only influence of the sun worth talking about is Total Solar Irradiance. But we have good reason to believe its not that simple.
Some of you might say that the effect of aerosols might be underestimated, meaning that a strong global dimming is masking global warming. Why is this wrong? Because their effect is almost certainly overestimated. Why? Because, models react more strongly to simulated volcanoes than real ones.
Love this quote, by the way:
“Give me four parameters, and I can fit an elephant. Give me five, and I can wiggle its trunk.”
Which just goes to show that models that are full of arbitrary parameters fitting reality is meaningless. Not, of course, that they do that all that well.
Ordinarily, it is against my policy to edit my posts, but I’m making an exception because I failed to address another point. I was defending Patrick Michaels and Ross McKitrick’s paper (in which they claim that half of recent warming isn’t real) from a rather empty criticism by Arthur (I think?). Anyway, he pointed out what he thought was clever, that seeing as they addressed only the land data, their reducing the land warming should only reduce global warming by 15%, because land is only 30% of the earth surface, assuming no big errors in the sea surface data. Well, there are to reasons he’s completely wrong. First, as Steve pointed out, their are errors in the SST data. Well, there’s that, an then there is the fact that he has assumed that the contribution of the oceans to warming should be just as big as the land (by area). If the ocean is warming less than the land, then this assumption is false. Well, using the satellite data, the answer is that the trend is less than the that on land (less than the satellite land data, so implicitly less than the GISS or other surface station data.) So basically, there isn’t warming the ocean big enough to save him.
EDIT: Sorry, reading it again, something was incredibly vague. I’m not changing what i said or meant, I just left a word or to out do to typing quickly.