Gokul43201 said:
From that paper: If Hansen et al say a 17-year period is too brief for precise assessment, how is it fair to then make comparisons to an even briefer 10-year period of data?
Can you find a paper that talks about meaningful predictions for a 10-year period? We can then look at what that paper says.
I had indeed Hansen's paper in mind, as this was discussed in the Earth forum. I agree of course that "climate predictions over 10 years" are a bit short, but then a lot of fuzz was made about the quick rise in the 1980-1990-ies. So if 10 or 20 years are sufficient to "prove beyond doubt" the *dramatic* heating, then it should be worrisome that in the next 10 years, this is contradicted. Especially because the dramatic rise of the last decades was also in part used to estimate the "feedback amplification" for the CO2 forcing.
This is why it will only be possible to have any kind of real scientific certainty of any claim about climate change only at least 30 to 50 years from now. Anybody who claims anything with "scientific certainty" before that (theory, prediction, and significant experimental verification) is taking his working hypothesis for a fact. You say it yourself: even 17 years is not enough. "Climate change" has been with us since the 1990-ies. If models are made up now, and if their predictions need testing for 30 years, then we cannot have the typical "model prediction + data falsification" before 30 years or so from now. Only then, if the predictions and the data are coincident, we can start to have some form of scientific certainty.
We have no scientific certainty that the Higgs exists. Only when sufficient data will show it in the LHC, we will know with some form of scientific certainty. A climate model that makes any prediction *now* will need at least 30 years for it to be tested against noisy data. Before that, we cannot scientifically be certain.
The other part of the hockeystick that was "misleading" was the very flat part in the past. It showed the striking contrast between the sudden rise in the last decades, to an almost flat temperature record for the last 1000 years or more. I don't have to dig up the entire discussion, it is very well resumed in the wiki article:
http://en.wikipedia.org/wiki/Hockey_stick_graph and has been discussed over and over in the Earth forum. I know that wiki is not a scientific journal, but I can't write any better summary than what's written there. I take it that the discussion is fair, as it corresponds to things I've seen in different places.
Let us not forget what was the purpose of the hockey stick. It was not to show that there has been a warming during the last several decades. I don't think anyone can deny this - it is in the instrumental record. The purpose of the hockey stick was to demonstrate that what was happening in the last few decades (even the last century or so) was totally exceptional, an obvious deviation from the "natural course of things" in such an evident and dramatic way, that even a layman could evidently see that we were screwing up things.
If you have a flat curve for a thousand years, and then you see a dramatic and almost linear rise for the last century or so, then nobody has any doubts anymore. This is "scientifically established beyond doubt". What is happening now has never happened before, and it is not a 3 sigma effect. It is a 100 sigma effect. And that drama is almost completely absent in more detailled studies that have been done more recently.
Yes, there's still a temperature rise. Nobody is denying that. But the drama is gone.
But please, don't understand me wrong. I'm not saying that there is no warming. I'm not saying that there is no AGW, or that there is not going to be any dramatic AGW. This is not my point. My point is that the "scientific certainty" that has been displayed, and that has been used and widely published and communicated, was wrong.
If you look at the two plots in the wiki article, the upper one the famous "hockey stick", and the lower one, more recent and more thorough studies, then it should be obvious that the *power to convince* of the first is far more dramatic than the second, no ?
That said, if you ask for my personal opinion, if I have to bet anything, I would bet on AGW. Hey, I'm a strong proponent for nuclear power and AGW is one of my main motives. I think it is a very plausible hypothesis. But there's a difference between a "plausible hypothesis" and "a scientific reality". I think - to answer your other post - that there's a world of difference between the certainty I have that the sun will rise tomorrow (Newtonian physics) and that the temperature will rise with 6 degrees in 100 years. The last is only on the level of "I think the Higgs exists".
It might be that the Higgs doesn't exist. I would be surprised. I think it exists. But I keep open the possibility that it doesn't exist. I'm not "scientifically certain" that it exists. Only experiment will tell. It cannot be that at the sun will not rise tomorrow. I'm scientifically certain that the sun will rise tomorrow. If ever the sun doesn't rise tomorrow, then about everything I know is wrong.
