Richard,

You completely misrepresent the report by taking the quotes out of context - I note your constant use of elipses to remove sections that don't support your argument.

Bob claimed Mann's report has been "totally discredited". The NSA report says Mann's basic conclusions have been supported by subsequent evidence.

You said the report showed Mann's study was 'unverifiable'. Your strategic use of elipses tells me you know this is not true.

I said the report showed subsequent evidence 'confirmed' Mann's basic thesis, and it does.

David and Cathy, please see ChrisC's link to realclimate and its discussion of the hockey stick:

http://www.realclimate.org/index.php/archives/2005/02/dummies-guide-to-the-latest-hockey-stick-controversy/

In particular, see answers to questions 8 and 9.

Even if you continue to believe Mann has been 'discredited', the fact remains subsequent evidence supports his basic claim - and that cannot be denied.

Skellett,

The conclusion by the NAS or anyone else that the late 20th century was "warmer than the last few hundred years" is about as surprising as the statement that "the sun will rise tomorrow". It is a scientifically trivial statement.

The whole issue with Mann's work was that it spanned back over the time of the Mediaeval Warm Period (MWP), and allowed pro-IPCC proponents to say that the late 20th century temperature peak was the "warmest in the last 1000 years".

As Bob Carter says, this "disproving" of the MWP - which was the pivotal and intended point of Mann's work - is now utterly discredited.

Rather than defending the indefensible, why not instead get to grips with the real situation (which is that the late 20th century warming is unusual in neither rate nor magnitude) and its implications (which are that there is no need for alarmist measures on climate change, such as the Kyoto Protocol)?

Cathy

Cathy,

You appear to believe in Myth #3, please refer to the following:

http://www.realclimate.org/index.php?p=11

It's a bit rich for you to demand that I "get to grips with the real situation" when you preface your demand with obvious untruths.

Science rarely gives us absolutely certain answers. Sometimes but rarely. Most of the time the best science can do is develop theories that explain and predict observed phenomena, and if contrary phenomena occur (as often happens), then the theories are refined to accomodate them.

Although the evidence is not beyond dispute, the modest rises in global temperature which have occurred during a period when CO2 levels have risen sharply, and the historical correspondence between rising temperatures and carbon levels, although not proven to be causally linked, do give us reason to be very concerned.

To those who say we should drop everything and cease our carbon emissions to address this 'crisis' I think that is an over-reaction. But to those who say, that simply because we don't have irrefutable truth, we should do nothing, that is a under reaction. We have to act on the best available information and as that information improves, we have refine our action.

We are like motorists speeding along the freeway who see flashing lights in the distance up ahead. Do we know it's unsafe to keep speeding along? No, but we ought to slow down just the same, and make ready to stop if necessary. Yes, slowing down will cost us, and unecessarily if it turns out the flashing light was not an issue for us, but safety is an issue for both a car on the freeway and our humble civillisation.

good to hear both sides of the story...

Puzzling that in the current debate on AGW we hear so little on what we now know about the last interglacial (known as Oxygen Isotope Substage 5e) some 117 - 125 ky ago (when global sea levels peaked at 4 - 6 m above present day levels). During that period atmospheric CO2 levels, based on ice core data (noting they possibly suffer some loss due to incomplete system closedness) were at least 300 ppmv (about 380 ppmv now). More significantly, all the isotopic and geomorphic evidence clearly suggests the last interglacial peak was fully bimodal with a peak separation of the order of 4 - 6 ky only. Now here we are today in the (Late?;-) Holocene and we know that conditions were significantly warmer over the period 1 - 8 ky ago (during the rise of human civilization). Proof? Sea levels on the NSW coast 7.5 - 2.5 ky ago went through a peak 1 - 1.5 m higher than now. Indeed, I can snorkel over the top of ~5 ky old coral bommies just off shore near my Wollongong house and it's a species of coral that no longer grows south of Qld! Anthropogenic? Obviously not! So are we simply heading into a 2nd interglacial peak? Who knows? What is th point I hear you cry. To me the point is utterly obvious. The system is clearly too big, too subtle, too oscillatory/variable for us to have any kind of decent predictive 'handle' on it as yet. It's tough enough predicting the weather 5 - 10 days hence!