Call me an old grump but the SPM for the IPCC AR4 report wasn't terribly exciting. Which was, perhaps no great surprise: having read the draft chapters, or at least skimmed them, it was clear that nothing revolutionary was going to appear. They throw in the phrase Warming of the climate system is unequivocal which is a nice sound-bite but was true for the TAR too. Climate sensitivity is likely to be within 2-4.5 oC, but since this is only a 66% statement its quite weak; though they do go on to diss > 4.5 oC a bit. And the attribution key text is:
Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations12. This is an advance since the TAR's conclusion that "most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations". Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns.
So our advance since the TAR is insertion of the word "very" ;-)? No, thats unfair. There has been a lot of science since then, but the basic view of humans causing climate change hasn't really altered very much.
[CJR says in a comment Might be a good thing... too much change in the fundamentals would lead to cries of, "look - they keep changing their mind about what they think!". Quite true, and what I meant to say myself. I was feeling a bit grumpy this morning due to negative theta in my model runs :-(. What this (the SPM; not -ve T) confirms is that much of the fundamentals in the TAR and before were correct, and are just being refined. Wasn't there a famous quote from Michaelson about that...? -W]
[Update: a href="http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/00…">RP Jr is obliged to admit that it wasn't as exciting as thought it might be - serve him right for believing the press... -W]
Might be a good thing... too much change in the fundamentals would lead to cries of, "look - they keep changing their mind about what they think!"
I believe that the assertion about "much of the fundamentals in the TAR and before were correct, and are just being refined" that you have in mind is actually due to Lord Kelvin himself who proclaimed in 1900:
"There is nothing new to be discovered in physics now. All that remains is more and more precise measurement."
A few months later, Planck described the black body and started quantum theory, eventually showing that all previously envisioned classical ideas about continuous observables and strict determinism were wrong.
Five years later, Einstein also discovered special relativity and later general relativity, showing that all previous ideas about space and time were fundamentally incorrect, too.
It takes a courage to repeat Kelvin's monumentally wrong prediction again in 2007. Actually, is it courage or something else? We report, you decide.
Don't give up string theory for the history business, Lubos.
To me the most interesting change is that ice flow is no longer included in sea level rise estimates.
I see it as a symptom of how much recent discoveries about ice sheet dynamics have shaken things up.
Lubos: I'd like to note you used a quote from over a hundred years ago and a hundred years of scientific method have passed. That any science can be overturned is not proof of anything. How anyone with a PhD can commit such an obvious logical fallacy is quite frankly beyond belief.
Dear Geoff, I am used to these silly comments of intellectual dwarves like you - this is what dwarves do. The only thing I have argued is that science by its very definition is a process of permanent evolution of our knowledge and refinements and everyone who builds on the assumption that it must be otherwise is an obscurantist and an intellectually defective zealot. This includes both William Connolley as well as you.
I have also pointed out that Connolley has used a citation - he used it himself - that turned out to be as wrong as possible, and it didn't need 100 years to be identified as a mistake: in 3 months, it was clear that Kelvin was being unrealistic and the amount of wrongness in his prediction was spectacular.
These guys had much more accurate measurements and much more solid principles than anly Connolley-like climate pseudoscientist today can dream about. Still, they were wrong. If someone deliberately builds on consensus or even allows consensus to change his opinions, he is intellectually worthless and redundant piece of crap.
[Dear Lubos you can be rather unthinking at time, of course I knew the meaning of the cite I used. Nonetheless, the mere fact that the answers now are much the same as they were 5 years ago doesn't make the answers wrong as you'd like to believe -W]
"I am used to these silly comments of intellectual dwarves like you"
Lubos wouldn't be the first person who thought he didn't need to be honest because he was so "clever".
Lubos...you might want to scurry over to the Prometheus blog and drop your bon mots over there. I'm sure that crowd would be delighted with your wit.
I am glad to say that I called that one right and told RP jr. not to believe any press leaks. The bad news is that Benny agreed with me ;-(